Merge pull request #173 from Unity-Technologies/categorical-parameter-fixes

Fixed and polished a few Randomization UI elements

com.unity.perception/CHANGELOG.md

 * Can now render intermediate frames between captures.
 * Capture can now be triggered manually using a function call, instead of automatic capturing on a schedule.
 
+Categorical Parameters will now validate that their specified options are unique at runtime.
+
-Randomizers now access their parent scenario through the static activeScenario property
+Randomizers now access their parent scenario through the static activeScenario property.
 
 Unique seeds per Sampler have been replaced with one global random seed configured via the ScenarioConstants of a Scenario
 
 
 RandomizerTagManager.Query<T>() now returns RandomizerTags directly instead of the GameObjects attached to said tags
 
-Semantic Segmentation Labeler now places data in folders with randomized filenames
+Semantic Segmentation Labeler now places data in folders with randomized filenames.
+The uniform toggle on Categorical Parameters will now reset the Parameter's probability weights to be uniform.
 
 ### Deprecated
 
 
 Semantic Segmentation Labeler now produces output in the proper form for distributed data generation on Unity Simulation by placing output in randomized directory names
 
-Texture Randomizer is now compatible with HDRP
+Texture Randomizer is now compatible with HDRP.
+
+Categorical Parameters no longer produce errors when deleting items from long options lists.
+Parameter, ISampler, and non-generic Sampler class UIs now render properly in MonoBehaviours and ScriptableObjects.
 
 ## [0.6.0-preview.1] - 2020-12-03
 

com.unity.perception/Editor/Randomization/Editors/PerceptionEditorAnalytics.cs

 using System;
 using JetBrains.Annotations;
-using UnityEditor;
-namespace UnityEngine.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
+        const string k_VendorKey = "unity.perception";
+        const string k_RunInUnitySimulationName = "runinunitysimulation";
-        const string k_VendorKey = "unity.perception";
-        const string k_RunInUnitySimulationName = "runinunitysimulation";
-        static bool s_IsRegistered = false;
+        static bool s_IsRegistered;
 
         static bool TryRegisterEvents()
         {
-            bool success = true;
+            var success = true;
             success &= EditorAnalytics.RegisterEventWithLimit(k_RunInUnitySimulationName, k_MaxEventsPerHour, k_MaxItems,
                 k_VendorKey) == AnalyticsResult.Ok;
 
 
-        enum RunStatus
-        {
-            Started,
-            Failed,
-            Succeeded
-        }
-
-        struct RunInUnitySimulationData
-        {
-            [UsedImplicitly]
-            public string runId;
-            [UsedImplicitly]
-            public int totalIterations;
-            [UsedImplicitly]
-            public int instanceCount;
-            [UsedImplicitly]
-            public string existingBuildId;
-            [UsedImplicitly]
-            public string errorMessage;
-            [UsedImplicitly]
-            public string runExecutionId;
-            [UsedImplicitly]
-            public string runStatus;
-        }
-
-            var data = new RunInUnitySimulationData()
+            var data = new RunInUnitySimulationData
             {
                 runId = runId.ToString(),
                 totalIterations = totalIterations,
             if (!TryRegisterEvents())
                 return;
 
-            var data = new RunInUnitySimulationData()
+            var data = new RunInUnitySimulationData
             {
                 runId = runId.ToString(),
                 errorMessage = errorMessage,
             if (!TryRegisterEvents())
                 return;
 
-            var data = new RunInUnitySimulationData()
+            var data = new RunInUnitySimulationData
             {
                 runId = runId.ToString(),
                 runExecutionId = runExecutionId,
+        }
+
+        enum RunStatus
+        {
+            Started,
+            Failed,
+            Succeeded
+        }
+
+        struct RunInUnitySimulationData
+        {
+            [UsedImplicitly]
+            public string runId;
+            [UsedImplicitly]
+            public int totalIterations;
+            [UsedImplicitly]
+            public int instanceCount;
+            [UsedImplicitly]
+            public string existingBuildId;
+            [UsedImplicitly]
+            public string errorMessage;
+            [UsedImplicitly]
+            public string runExecutionId;
+            [UsedImplicitly]
+            public string runStatus;
         }
     }
 }

com.unity.perception/Editor/Randomization/Editors/RunInUnitySimulationWindow.cs

 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using Unity.Simulation.Client;
-using UnityEditor;
-using UnityEngine.Experimental.Perception.Randomization.Editor;
+using UnityEngine;
-namespace UnityEngine.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
 {
     class RunInUnitySimulationWindow : EditorWindow
     {
-        SysParamDefinition m_SysParam;
+        IntegerField m_InstanceCountField;
+        ObjectField m_MainSceneField;
+        Button m_RunButton;
+        ObjectField m_ScenarioField;
+        SysParamDefinition m_SysParam;
-        IntegerField m_InstanceCountField;
-        ObjectField m_MainSceneField;
-        ObjectField m_ScenarioField;
-        Button m_RunButton;
 
         [MenuItem("Window/Run in Unity Simulation")]
         static void ShowWindow()
         }
 
         /// <summary>
-        /// Enables a visual element to remember values between editor sessions
+        ///     Enables a visual element to remember values between editor sessions
         /// </summary>
         /// <param name="element">The visual element to enable view data for</param>
         static void SetViewDataKey(VisualElement element)
             var sysParamDefinitions = API.GetSysParams();
             var sysParamMenu = root.Q<ToolbarMenu>("sys-param");
             foreach (var definition in sysParamDefinitions)
-            {
                 sysParamMenu.menu.AppendAction(
                     definition.description,
                     action =>
                     });
-            }
 
             sysParamMenu.text = sysParamDefinitions[0].description;
             m_SysParam = sysParamDefinitions[0];
                 runGuid,
                 m_TotalIterationsField.value,
                 m_InstanceCountField.value,
-                existingBuildId: null);
+                null);
             try
             {
                 ValidateSettings();
 
                 var appParamsString = JsonConvert.SerializeObject(configuration, Formatting.Indented);
                 var appParamId = API.UploadAppParam(appParamName, appParamsString);
-                appParamIds.Add(new AppParam()
+                appParamIds.Add(new AppParam
                 {
                     id = appParamId,
                     name = appParamName,
-                EditorUtility.DisplayProgressBar("Unity Simulation Run", $"Uploading app-param-ids for instances: {i + 1}/{m_InstanceCountField.value}", progressStart + progressIncrement * i);
+                EditorUtility.DisplayProgressBar(
+                    "Unity Simulation Run",
+                    $"Uploading app-param-ids for instances: {i + 1}/{m_InstanceCountField.value}",
+                    progressStart + progressIncrement * i);
             }
 
             return appParamIds;
 
             Debug.Log($"Generated app-param ids: {appParams.Count}");
 
-            EditorUtility.DisplayProgressBar("Unity Simulation Run", $"Uploading run definition...", 0.9f);
+            EditorUtility.DisplayProgressBar("Unity Simulation Run", "Uploading run definition...", 0.9f);
 
             var runDefinitionId = API.UploadRunDefinition(new RunDefinition
             {
             });
             Debug.Log($"Run definition upload complete: run definition id {runDefinitionId}");
 
-            EditorUtility.DisplayProgressBar("Unity Simulation Run", $"Executing run...", 0.95f);
+            EditorUtility.DisplayProgressBar("Unity Simulation Run", "Executing run...", 0.95f);
 
             var run = Run.CreateFromDefinitionId(runDefinitionId);
             run.Execute();

com.unity.perception/Editor/Randomization/Editors/ScenarioBaseEditor.cs

-using System.Collections;
-using System.Linq;
-using UnityEditor;
-using UnityEditor.UIElements;
+using UnityEngine;
-using UnityEngine.Experimental.Perception.Randomization.VisualElements;
+using Object = UnityEngine.Object;
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
-    class ScenarioBaseEditor : UnityEditor.Editor
+    class ScenarioBaseEditor : Editor
+        VisualElement m_ConstantsListVisualContainer;
+        VisualElement m_InspectorPropertiesContainer;
+        VisualElement m_RandomizerListPlaceholder;
+        VisualElement m_Root;
-        VisualElement m_Root;
-        VisualElement m_InspectorPropertiesContainer;
-        VisualElement m_ConstantsListVisualContainer;
-        VisualElement m_RandomizerListPlaceholder;
 
         public override VisualElement CreateInspectorGUI()
         {
             m_ConstantsListVisualContainer = m_Root.Q<VisualElement>("constants-list");
             m_ConstantsListVisualContainer.Clear();
 
-            var iterator = m_SerializedObject.GetIterator();
-            if (iterator.NextVisible(true))
+
+            var iterator = m_SerializedObject.GetIterator();
+            iterator.NextVisible(true);
+            iterator.NextVisible(false);
+            do
-                do
+                switch (iterator.name)
-                    switch (iterator.name)
+                    case "m_Randomizers":
+                        m_RandomizerListPlaceholder.Add(new RandomizerList(iterator.Copy()));
+                        break;
+                    case "constants":
+                        m_HasConstantsField = true;
+                        UIElementsEditorUtilities.CreatePropertyFields(iterator.Copy(), m_ConstantsListVisualContainer);
+                        break;
+                    default:
-                        case "m_Script":
-                            break;
-                        case "m_Randomizers":
-                            m_RandomizerListPlaceholder.Add(new RandomizerList(iterator.Copy()));
-                            break;
-                        case "constants":
-                            m_HasConstantsField = true;
-                            CreateConstantsFieldsWithToolTips(iterator.Copy());
-                            break;
-                        default:
-                        {
-                            foundProperties = true;
-                            var propertyField = new PropertyField(iterator.Copy());
-                            propertyField.Bind(m_SerializedObject);
-                            m_InspectorPropertiesContainer.Add(propertyField);
-                            break;
-                        }
+                        foundProperties = true;
+                        var propertyField = UIElementsEditorUtilities.CreatePropertyField(iterator, m_Scenario.GetType());
+                        m_InspectorPropertiesContainer.Add(propertyField);
+                        break;
-                } while (iterator.NextVisible(false));
-            }
+                }
+            } while (iterator.NextVisible(false));
 
             if (!foundProperties)
                 m_InspectorPropertiesContainer.style.display = new StyleEnum<DisplayStyle>(DisplayStyle.None);
                 m_InspectorPropertiesContainer.style.marginBottom = 0;
                 m_ConstantsListVisualContainer.style.display = new StyleEnum<DisplayStyle>(DisplayStyle.None);
             }
-        }
-
-        void CreateConstantsFieldsWithToolTips(SerializedProperty constantsProperty)
-        {
-            constantsProperty.NextVisible(true);
-            do
-            {
-                var constantsPropertyField = new PropertyField(constantsProperty.Copy());
-                constantsPropertyField.Bind(m_SerializedObject);
-
-                var originalField = target.GetType().GetField("constants").FieldType.GetField(constantsProperty.name);
-                var tooltipAttribute = originalField.GetCustomAttributes(true).ToList().Find(att => att.GetType() == typeof(TooltipAttribute));
-                if (tooltipAttribute != null)
-                    constantsPropertyField.tooltip = (tooltipAttribute as TooltipAttribute)?.tooltip;
-
-                m_ConstantsListVisualContainer.Add(constantsPropertyField);
-
-            } while (constantsProperty.NextVisible(true));
         }
     }
 }

com.unity.perception/Editor/Randomization/PropertyDrawers/ColorHsvaDrawer.cs

-using UnityEditor;
+using System;
+using UnityEngine;
-namespace UnityEngine.Perception.Randomization.Editor.PropertyDrawers
+namespace UnityEditor.Experimental.Perception.Randomization.PropertyDrawers
 {
     [CustomPropertyDrawer(typeof(ColorHsva), true)]
     class ColorHsvaDrawer : PropertyDrawer

com.unity.perception/Editor/Randomization/PropertyDrawers/ParameterDrawer.cs

 using System;
-using UnityEditor;
+using UnityEngine;
-namespace UnityEngine.Perception.Randomization.Editor.PropertyDrawers
+namespace UnityEditor.Experimental.Perception.Randomization.PropertyDrawers
 {
     [CustomPropertyDrawer(typeof(Parameter), true)]
     class ParameterDrawer : PropertyDrawer

com.unity.perception/Editor/Randomization/Uxml/Sampler/FloatRangeElement.uxml

 <UXML xmlns="UnityEngine.UIElements" xmlns:editor="UnityEditor.UIElements">
     <VisualElement>
+        <Style src="../../Uss/Styles.uss"/>
         <VisualElement style="flex-direction: row; margin: 1px, 1px, 1px, 3px;">
             <Label text="Range" class="unity-base-field__label" style="min-width: 147;"/>
             <VisualElement class="sampler__float-range" style="flex-grow: 1; flex-direction: row;">

com.unity.perception/Editor/Randomization/Uxml/Sampler/SamplerElement.uxml

 <UXML xmlns="UnityEngine.UIElements" xmlns:editor="UnityEditor.UIElements">
-    <VisualElement name="sampler-template" style="margin-bottom: 4px;">
+    <VisualElement style="margin-bottom: 4px;">
-        <VisualElement style="flex-direction: row; align-items: center;">
-            <Label name="sampler-name" text="Sampler Name" class="unity-base-field__label"/>
-            <editor:ToolbarMenu name="sampler-type-dropdown" text="Placeholder Sampler Type" class="sampler__type-menu"/>
-        </VisualElement>
+        <Label name="display-name" text="Sampler Name" class="unity-base-field__label"/>
         <VisualElement name="fields-container" style="margin-left: 18px;"/>
     </VisualElement>
 </UXML>

com.unity.perception/Editor/Randomization/Uxml/Sampler/SamplerElement.uxml.meta

 fileFormatVersion: 2
-guid: e91be9c80e944358b231c125be80a749
-timeCreated: 1594847524
+guid: a4752f9d99d8497e9a147942da225b5f
+timeCreated: 1612043461

com.unity.perception/Editor/Randomization/VisualElements/Parameter/CategoricalOptionElement.cs

 using System;
-using UnityEditor;
+using UnityEngine;
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
-        int m_Index;
+        int m_Index;
         SerializedProperty m_ProbabilitiesProperty;
 
         internal CategoricalOptionElement(
             m_CategoryProperty = categoryProperty;
             m_ProbabilitiesProperty = probabilitiesProperty;
-
-            var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
-                $"{StaticData.uxmlDir}/Parameter/CategoricalOptionElement.uxml");
-            template.CloneTree(this);
+            // Reset this categorical item's UI
+            Clear();
+            var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
+                $"{StaticData.uxmlDir}/Parameter/CategoricalOptionElement.uxml");
+            template.CloneTree(this);
+
             m_Index = i;
             var indexLabel = this.Q<Label>("index-label");
             indexLabel.text = $"[{m_Index}]";
             option.BindProperty(optionProperty);
+
+            // Remove the redundant element label to save space
             var label = option.Q<Label>();
             label.parent.Remove(label);
 
             else
             {
                 probability.SetEnabled(true);
-                probability.RegisterValueChangedCallback((evt) =>
+                probability.RegisterValueChangedCallback(evt =>
                 {
                     if (evt.newValue < 0f)
                         probability.value = 0f;

com.unity.perception/Editor/Randomization/VisualElements/Parameter/ColorHsvaField.cs

-using UnityEditor;
+using System;
+using UnityEngine;
-namespace UnityEngine.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
-        SerializedProperty m_Property;
+        SerializedProperty m_A;
+        SerializedProperty m_Property;
-        SerializedProperty m_A;
 
         public ColorHsvaField(SerializedProperty property)
         {

com.unity.perception/Editor/Randomization/VisualElements/Parameter/DrawerParameterElement.cs

-using UnityEditor;
-using UnityEngine.Experimental.Perception.Randomization.Editor;
-using UnityEngine.Experimental.Perception.Randomization.Parameters;
+using System;
-namespace UnityEngine.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
-        Parameter m_Parameter;
+        const string k_CollapsedParameterClass = "collapsed";
-        const string k_CollapsedParameterClass = "collapsed";
-
-        bool collapsed
-        {
-            get => m_Collapsed.boolValue;
-            set
-            {
-                m_Collapsed.boolValue = value;
-                m_Property.serializedObject.ApplyModifiedPropertiesWithoutUndo();
-                if (value)
-                    AddToClassList(k_CollapsedParameterClass);
-                else
-                    RemoveFromClassList(k_CollapsedParameterClass);
-            }
-        }
 
         public DrawerParameterElement(SerializedProperty property)
         {
 
             var drawer = this.Q<VisualElement>("drawer");
             drawer.Add(new ParameterElement(property));
+        }
+
+        bool collapsed
+        {
+            get => m_Collapsed.boolValue;
+            set
+            {
+                m_Collapsed.boolValue = value;
+                m_Property.serializedObject.ApplyModifiedPropertiesWithoutUndo();
+                if (value)
+                    AddToClassList(k_CollapsedParameterClass);
+                else
+                    RemoveFromClassList(k_CollapsedParameterClass);
+            }
         }
     }
 }

com.unity.perception/Editor/Randomization/VisualElements/Parameter/ParameterElement.cs

 using System;
 using System.Collections.Generic;
-using UnityEditor;
-using UnityEngine.Experimental.Perception.Randomization.Editor;
+using UnityEngine;
+using Object = UnityEngine.Object;
-namespace UnityEngine.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
 {
     class ParameterElement : VisualElement
     {
-        Parameter parameter => (Parameter)StaticData.GetManagedReferenceValue(m_SerializedProperty);
-        CategoricalParameterBase categoricalParameter => (CategoricalParameterBase)parameter;
-
         public ParameterElement(SerializedProperty property)
         {
             var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
             CreatePropertyFields();
         }
 
+        Parameter parameter => (Parameter)StaticData.GetManagedReferenceValue(m_SerializedProperty);
+        CategoricalParameterBase categoricalParameter => (CategoricalParameterBase)parameter;
+
         void CreatePropertyFields()
         {
             m_PropertiesContainer.Clear();
                 return;
             }
 
-            var currentProperty = m_SerializedProperty.Copy();
+
+            var currentProperty = m_SerializedProperty.Copy();
-            {
-                    if (currentProperty.type.Contains("managedReference") &&
-                        currentProperty.managedReferenceFieldTypename == StaticData.samplerSerializedFieldType)
-                        m_PropertiesContainer.Add(new SamplerElement(currentProperty.Copy(), parameter));
-                    else
-                    {
-                        var propertyField = new PropertyField(currentProperty.Copy());
-                        propertyField.Bind(currentProperty.serializedObject);
-                        m_PropertiesContainer.Add(propertyField);
-                    }
+                    var propertyField = new PropertyField(currentProperty.Copy());
+                    propertyField.Bind(currentProperty.serializedObject);
+                    m_PropertiesContainer.Add(propertyField);
-            }
         }
 
         void CreateCategoricalParameterFields()
             listView.style.flexGrow = 1.0f;
             listView.style.height = new StyleLength(listView.itemHeight * 4);
 
-            VisualElement MakeItem() => new CategoricalOptionElement(
-                optionsProperty, probabilitiesProperty);
+            VisualElement MakeItem()
+            {
+                return new CategoricalOptionElement(
+                    optionsProperty, probabilitiesProperty);
+            }
+
             listView.makeItem = MakeItem;
 
             void BindItem(VisualElement e, int i)
                     listView.Refresh();
                 };
             }
+
             listView.bindItem = BindItem;
 
             var addOptionButton = template.Q<Button>("add-option");
                 optionsProperty.arraySize++;
+                var newOption = optionsProperty.GetArrayElementAtIndex(optionsProperty.arraySize - 1);
+                switch (newOption.propertyType)
+                {
+                    case SerializedPropertyType.ObjectReference:
+                        newOption.objectReferenceValue = null;
+                        break;
+                    case SerializedPropertyType.String:
+                        newOption.stringValue = string.Empty;
+                        break;
+                }
+
                 m_SerializedProperty.serializedObject.ApplyModifiedProperties();
                 listView.itemsSource = categoricalParameter.probabilities;
                 listView.Refresh();
             var addFolderButton = template.Q<Button>("add-folder");
             if (categoricalParameter.sampleType.IsSubclassOf(typeof(Object)))
-            {
                 addFolderButton.clicked += () =>
                 {
                     var folderPath = EditorUtility.OpenFolderPanel(
                         optionProperty.objectReferenceValue = categories[i];
                         probabilityProperty.floatValue = uniformProbability;
                     }
+
-            }
             else
                 addFolderButton.style.display = new StyleEnum<DisplayStyle>(DisplayStyle.None);
 
             {
                 if (Mathf.Approximately(scrollView.verticalScroller.highValue, 0f))
                     return;
-                if ((scrollView.scrollOffset.y <= 0f && evt.delta.y < 0f) ||
+                if (scrollView.scrollOffset.y <= 0f && evt.delta.y < 0f ||
                     scrollView.scrollOffset.y >= scrollView.verticalScroller.highValue && evt.delta.y > 0f)
                     evt.StopImmediatePropagation();
             });
             uniformToggle.BindProperty(uniformProperty);
-            void ToggleProbabilityFields(bool toggle)
-            {
-                if (toggle)
-                    listView.AddToClassList("collapsed");
-                else
-                    listView.RemoveFromClassList("collapsed");
-            }
-            ToggleProbabilityFields(uniformToggle.value);
+
+            if (uniformToggle.value)
+                listView.AddToClassList("collapsed");
+            else
+                listView.RemoveFromClassList("collapsed");
+
-                uniformToggle.RegisterCallback<ChangeEvent<bool>>(evt => ToggleProbabilityFields(evt.newValue));
+                uniformToggle.RegisterCallback<ChangeEvent<bool>>(evt =>
+                {
+                    listView.ToggleInClassList("collapsed");
+                    if (!evt.newValue)
+                        return;
+                    var numOptions = optionsProperty.arraySize;
+                    var uniformProbabilityValue = 1f / numOptions;
+                    for (var i = 0; i < numOptions; i++)
+                    {
+                        var probability = probabilitiesProperty.GetArrayElementAtIndex(i);
+                        probability.floatValue = uniformProbabilityValue;
+                    }
+
+                    m_SerializedProperty.serializedObject.ApplyModifiedProperties();
+                    listView.itemsSource = categoricalParameter.probabilities;
+                    listView.Refresh();
+                });
 
             m_PropertiesContainer.Add(template);
         }
             if (!folderPath.StartsWith(Application.dataPath))
                 throw new ApplicationException("Selected folder is not an asset folder in this project");
             var assetsPath = "Assets" + folderPath.Remove(0, Application.dataPath.Length);
-            var assetIds = AssetDatabase.FindAssets($"t:{assetType.Name}", new []{assetsPath});
+            var assetIds = AssetDatabase.FindAssets($"t:{assetType.Name}", new[] { assetsPath });
             var assets = new List<Object>();
             foreach (var guid in assetIds)
                 assets.Add(AssetDatabase.LoadAssetAtPath(AssetDatabase.GUIDToAssetPath(guid), assetType));

com.unity.perception/Editor/Randomization/VisualElements/Randomizer/AddRandomizerMenu.cs

 using System.Collections.Generic;
 using NUnit.Framework;
 using Unity.Mathematics;
-using UnityEditor;
-using UnityEngine.Experimental.Perception.Randomization.Editor;
-namespace UnityEngine.Experimental.Perception.Randomization.VisualElements
+namespace UnityEditor.Experimental.Perception.Randomization
+        VisualElement m_DirectoryChevron;
+        TextElement m_DirectoryLabelText;
+        Dictionary<string, HashSet<string>> m_MenuDirectories = new Dictionary<string, HashSet<string>>();
+        VisualElement m_MenuElements;
+        List<MenuItem> m_MenuItems = new List<MenuItem>();
+        Dictionary<string, List<MenuItem>> m_MenuItemsMap = new Dictionary<string, List<MenuItem>>();
+
+        RandomizerList m_RandomizerList;
+
+        string m_SearchString = string.Empty;
+
+        public AddRandomizerMenu(VisualElement parentElement, VisualElement button, RandomizerList randomizerList)
+        {
+            m_RandomizerList = randomizerList;
+            var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
+                $"{StaticData.uxmlDir}/Randomizer/AddRandomizerMenu.uxml");
+            template.CloneTree(this);
+            style.position = new StyleEnum<Position>(Position.Absolute);
+
+            var buttonPosition = button.worldBound.position;
+            var top = math.min(buttonPosition.y, parentElement.worldBound.height - 300);
+            style.top = top;
+            style.left = buttonPosition.x;
+
+            focusable = true;
+            RegisterCallback<FocusOutEvent>(evt =>
+            {
+                if (evt.relatedTarget == null || ((VisualElement)evt.relatedTarget).FindCommonAncestor(this) != this)
+                    ExitMenu();
+            });
+
+            var directoryLabel = this.Q<VisualElement>("directory-label");
+            directoryLabel.RegisterCallback<MouseUpEvent>(evt => { AscendDirectory(); });
+            m_DirectoryLabelText = this.Q<TextElement>("directory-label-text");
+            m_DirectoryChevron = this.Q<VisualElement>("directory-chevron");
+
+            var searchBar = this.Q<TextField>("search-bar");
+            searchBar.schedule.Execute(() => searchBar.ElementAt(0).Focus());
+            searchBar.RegisterValueChangedCallback(evt => searchString = evt.newValue);
+
+            m_MenuElements = this.Q<VisualElement>("menu-options");
+
+            CreateMenuItems();
+            DrawDirectoryItems();
+        }
+
         string currentPath
         {
             get => m_CurrentPath;
             }
         }
 
-        string m_SearchString = string.Empty;
         string searchString
         {
             get => m_SearchString;
             }
         }
 
-        RandomizerList m_RandomizerList;
-        VisualElement m_MenuElements;
-        TextElement m_DirectoryLabelText;
-        VisualElement m_DirectoryChevron;
-        Dictionary<string, List<MenuItem>> m_MenuItemsMap = new Dictionary<string, List<MenuItem>>();
-        Dictionary<string, HashSet<string>> m_MenuDirectories = new Dictionary<string, HashSet<string>>();
-        List<MenuItem> m_MenuItems = new List<MenuItem>();
-
-        class MenuItem
-        {
-            public Type randomizerType;
-            public string itemName;
-
-            public MenuItem(Type randomizerType, string itemName)
-            {
-                this.randomizerType = randomizerType;
-                this.itemName = itemName;
-            }
-        }
-
-        sealed class MenuItemElement : TextElement
-        {
-            public MenuItemElement(MenuItem menuItem, AddRandomizerMenu menu)
-            {
-                text = menuItem.itemName;
-                AddToClassList("randomizer__add-menu-directory-item");
-                RegisterCallback<MouseUpEvent>(evt => menu.AddRandomizer(menuItem.randomizerType));
-            }
-        }
-
-        sealed class MenuDirectoryElement : VisualElement
-        {
-            public MenuDirectoryElement(string directory, AddRandomizerMenu menu)
-            {
-                AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
-                    $"{StaticData.uxmlDir}/Randomizer/MenuDirectoryElement.uxml").CloneTree(this);
-                var pathItems = directory.Split('/');
-                this.Q<TextElement>("directory").text = pathItems[pathItems.Length - 1];
-                RegisterCallback<MouseUpEvent>(evt => menu.currentPath = directory);
-            }
-        }
-
-        public AddRandomizerMenu(VisualElement parentElement, VisualElement button, RandomizerList randomizerList)
-        {
-            m_RandomizerList = randomizerList;
-            var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
-                $"{StaticData.uxmlDir}/Randomizer/AddRandomizerMenu.uxml");
-            template.CloneTree(this);
-            style.position = new StyleEnum<Position>(Position.Absolute);
-
-            var buttonPosition = button.worldBound.position;
-            var top = math.min(buttonPosition.y, parentElement.worldBound.height - 300);
-            style.top = top;
-            style.left = buttonPosition.x;
-
-            focusable = true;
-            RegisterCallback<FocusOutEvent>(evt =>
-            {
-                if (evt.relatedTarget == null || ((VisualElement)evt.relatedTarget).FindCommonAncestor(this) != this)
-                    ExitMenu();
-            });
-
-            var directoryLabel = this.Q<VisualElement>("directory-label");
-            directoryLabel.RegisterCallback<MouseUpEvent>(evt => { AscendDirectory(); });
-            m_DirectoryLabelText = this.Q<TextElement>("directory-label-text");
-            m_DirectoryChevron = this.Q<VisualElement>("directory-chevron");
-
-            var searchBar = this.Q<TextField>("search-bar");
-            searchBar.schedule.Execute(() => searchBar.ElementAt(0).Focus());
-            searchBar.RegisterValueChangedCallback(evt => searchString = evt.newValue);
-
-            m_MenuElements = this.Q<VisualElement>("menu-options");
-
-            CreateMenuItems();
-            DrawDirectoryItems();
-        }
-
         void ExitMenu()
         {
             parent.Remove(this);
 
             var upperSearchString = searchString.ToUpper();
             foreach (var menuItem in m_MenuItems)
-            {
-            }
         }
 
         void CreateMenuItems()
                                     m_MenuDirectories.Add(path, new HashSet<string>());
                                 m_MenuDirectories[path].Add(childPath);
                             }
+
                             path = childPath;
                         }
 
                     rootList.Add(new MenuItem(randomizerType, randomizerType.Name));
                 }
             }
+
+        }
+
+        class MenuItem
+        {
+            public string itemName;
+            public Type randomizerType;
+
+            public MenuItem(Type randomizerType, string itemName)
+            {
+                this.randomizerType = randomizerType;
+                this.itemName = itemName;
+            }
+        }
+
+        sealed class MenuItemElement : TextElement
+        {
+            public MenuItemElement(MenuItem menuItem, AddRandomizerMenu menu)
+            {
+                text = menuItem.itemName;
+                AddToClassList("randomizer__add-menu-directory-item");
+                RegisterCallback<MouseUpEvent>(evt => menu.AddRandomizer(menuItem.randomizerType));
+            }
+        }
+
+        sealed class MenuDirectoryElement : VisualElement
+        {
+            public MenuDirectoryElement(string directory, AddRandomizerMenu menu)
+            {
+                AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
+                    $"{StaticData.uxmlDir}/Randomizer/MenuDirectoryElement.uxml").CloneTree(this);
+                var pathItems = directory.Split('/');
+                this.Q<TextElement>("directory").text = pathItems[pathItems.Length - 1];
+                RegisterCallback<MouseUpEvent>(evt => menu.currentPath = directory);
+            }
         }
     }
 }

com.unity.perception/Editor/Randomization/VisualElements/Randomizer/DragToReorderManipulator.cs

-using UnityEngine.Experimental.Perception.Randomization.VisualElements;
+using System;
+using UnityEditor.Experimental.Perception.Randomization;
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
+        VisualElement m_DragHandle;
+        VisualElement m_ParameterContainer;
-        VisualElement m_DragHandle;
-        VisualElement m_ParameterContainer;
 
         protected override void RegisterCallbacksOnTarget()
         {
 
             var randomizerIndex = m_RandomizerElement.parent.IndexOf(m_RandomizerElement);
             for (var i = 0; i < middlePoints.Length; i++)
-            {
-            }
+
             ReorderParameter(randomizerIndex, middlePoints.Length);
         }
 

com.unity.perception/Editor/Randomization/VisualElements/Randomizer/RandomizerElement.cs

 using System;
-using UnityEditor;
-using UnityEngine.Experimental.Perception.Randomization.Editor;
+using UnityEngine.Experimental.Perception.Randomization.Randomizers;
-namespace UnityEngine.Experimental.Perception.Randomization.VisualElements
+namespace UnityEditor.Experimental.Perception.Randomization
+        const string k_CollapsedParameterClass = "collapsed";
-        SerializedProperty m_Property;
-
-        Randomizers.Randomizer randomizer => (Randomizers.Randomizer)StaticData.GetManagedReferenceValue(m_Property);
-
-        public Type randomizerType => randomizer.GetType();
-
-        const string k_CollapsedParameterClass = "collapsed";
-
-        public RandomizerList randomizerList { get; }
-
-        public bool collapsed
-        {
-            get => m_Collapsed.boolValue;
-            set
-            {
-                m_Collapsed.boolValue = value;
-                m_Property.serializedObject.ApplyModifiedPropertiesWithoutUndo();
-                if (value)
-                    AddToClassList(k_CollapsedParameterClass);
-                else
-                    RemoveFromClassList(k_CollapsedParameterClass);
-            }
-        }
+        SerializedProperty m_Property;
 
         public RandomizerElement(SerializedProperty property, RandomizerList randomizerList)
         {
             FillPropertiesContainer();
         }
 
-        void FillPropertiesContainer()
-        {
-            m_PropertiesContainer.Clear();
-            var iterator = m_Property.Copy();
-            var nextSiblingProperty = m_Property.Copy();
-            nextSiblingProperty.NextVisible(false);
+        Randomizer randomizer => (Randomizer)StaticData.GetManagedReferenceValue(m_Property);
+
+        public Type randomizerType => randomizer.GetType();
+
+        public RandomizerList randomizerList { get; }
-            var foundProperties = false;
-            if (iterator.NextVisible(true))
+        public bool collapsed
+        {
+            get => m_Collapsed.boolValue;
+            set
-                do
-                {
-                    if (SerializedProperty.EqualContents(iterator, nextSiblingProperty))
-                        break;
-                    if (iterator.name == "<enabled>k__BackingField")
-                        continue;
-                    foundProperties = true;
-                    var propertyField = new PropertyField(iterator.Copy());
-                    propertyField.Bind(m_Property.serializedObject);
-                    m_PropertiesContainer.Add(propertyField);
-                } while (iterator.NextVisible(false));
+                m_Collapsed.boolValue = value;
+                m_Property.serializedObject.ApplyModifiedPropertiesWithoutUndo();
+                if (value)
+                    AddToClassList(k_CollapsedParameterClass);
+                else
+                    RemoveFromClassList(k_CollapsedParameterClass);
+        }
-            if (!foundProperties)
+        void FillPropertiesContainer()
+        {
+            m_PropertiesContainer.Clear();
+            UIElementsEditorUtilities.CreatePropertyFields(m_Property, m_PropertiesContainer);
+
+            if (m_PropertiesContainer.childCount == 0)
                 m_PropertiesContainer.style.display = new StyleEnum<DisplayStyle>(DisplayStyle.None);
         }
     }

com.unity.perception/Editor/Randomization/VisualElements/Randomizer/RandomizerList.cs

 using System;
-using System.Collections.Generic;
-using UnityEditor;
-using UnityEditor.UIElements;
-using UnityEngine.Experimental.Perception.Randomization.Editor;
-namespace UnityEngine.Experimental.Perception.Randomization.VisualElements
+namespace UnityEditor.Experimental.Perception.Randomization
-        SerializedProperty m_Property;
-
-        public ScenarioBase scenario => (ScenarioBase)m_Property.serializedObject.targetObject;
-
-        VisualElement inspectorContainer
-        {
-            get
-            {
-                var viewport = parent;
-                while (!viewport.ClassListContains("unity-inspector-main-container"))
-                    viewport = viewport.parent;
-                return viewport;
-            }
-        }
+        SerializedProperty m_Property;
 
         public RandomizerList(SerializedProperty property)
         {
                 m_Property.serializedObject.Update();
                 RefreshList();
             };
+        }
+
+        public ScenarioBase scenario => (ScenarioBase)m_Property.serializedObject.targetObject;
+
+        VisualElement inspectorContainer
+        {
+            get
+            {
+                var viewport = parent;
+                while (!viewport.ClassListContains("unity-inspector-main-container"))
+                    viewport = viewport.parent;
+                return viewport;
+            }
         }
 
         void RefreshList()

com.unity.perception/Editor/Randomization/VisualElements/Randomizer/RandomizerReorderingIndicator.cs

-using UnityEngine.UIElements;
+using System;
+using UnityEngine.UIElements;
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
 {
     class RandomizerReorderingIndicator : VisualElement
     {

com.unity.perception/Editor/Randomization/VisualElements/Sampler/FloatRangeElement.cs

-using UnityEngine;
-using UnityEditor;
+using System;
+using UnityEngine;
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
 {
     class FloatRangeElement : VisualElement
     {

com.unity.perception/Editor/Randomization/VisualElements/Sampler/SamplerElement.cs

 using System;
-using System.Linq;
-using UnityEditor;
-using UnityEditor.UIElements;
-using UnityEngine.Experimental.Perception.Randomization.Parameters;
-using UnityEngine.Experimental.Perception.Randomization.Samplers;
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
+namespace UnityEditor.Experimental.Perception.Randomization
-        Parameter m_Parameter;
-        ISampler m_Sampler;
-        SerializedProperty m_Property;
-        SerializedProperty m_RangeProperty;
-        VisualElement m_Properties;
-        ToolbarMenu m_SamplerTypeDropdown;
-
-        public SamplerElement(SerializedProperty property, Parameter parameter)
+        public SamplerElement(SerializedProperty property)
-            m_Property = property;
-            m_Parameter = parameter;
-            m_Sampler = GetSamplerFromSerializedObject();
-
-            if (m_Sampler == null)
-                CreateSampler(typeof(UniformSampler));
-
-            var samplerName = this.Q<Label>("sampler-name");
-            samplerName.text = UppercaseFirstLetter(m_Property.name);
-
-            m_Properties = this.Q<VisualElement>("fields-container");
-            m_SamplerTypeDropdown = this.Q<ToolbarMenu>("sampler-type-dropdown");
-            m_SamplerTypeDropdown.text = SamplerUtility.GetSamplerDisplayName(m_Sampler.GetType());;
-            foreach (var samplerType in StaticData.samplerTypes)
-            {
-                var displayName = SamplerUtility.GetSamplerDisplayName(samplerType);;
-                m_SamplerTypeDropdown.menu.AppendAction(
-                    displayName,
-                    a => { ReplaceSampler(samplerType); },
-                    a => DropdownMenuAction.Status.Normal);
-            }
-            CreatePropertyFields();
-        }
-
-        void ReplaceSampler(Type samplerType)
-        {
-            CreateSampler(samplerType);
-            m_SamplerTypeDropdown.text = SamplerUtility.GetSamplerDisplayName(samplerType);
-            CreatePropertyFields();
-        }
-
-        void CreateSampler(Type samplerType)
-        {
-            var newSampler = (ISampler)Activator.CreateInstance(samplerType);
-            CopyFloatRangeToNewSampler(newSampler);
-            m_Sampler = newSampler;
-            m_Property.managedReferenceValue = newSampler;
-            m_Property.serializedObject.ApplyModifiedProperties();
-        }
-
-        void CopyFloatRangeToNewSampler(ISampler newSampler)
-        {
-            if (m_RangeProperty == null)
-                return;
-
-            var rangeField = newSampler.GetType().GetField(m_RangeProperty.name);
-            if (rangeField == null)
-                return;
-
-            var range = new FloatRange(
-                m_RangeProperty.FindPropertyRelative("minimum").floatValue,
-                m_RangeProperty.FindPropertyRelative("maximum").floatValue);
-            rangeField.SetValue(newSampler, range);
-        }
-
-        void CreatePropertyFields()
-        {
-            m_RangeProperty = null;
-            m_Properties.Clear();
-            var currentProperty = m_Property.Copy();
-            var nextSiblingProperty = m_Property.Copy();
-            nextSiblingProperty.NextVisible(false);
-
-            if (currentProperty.NextVisible(true))
-            {
-                do
-                {
-                    if (SerializedProperty.EqualContents(currentProperty, nextSiblingProperty))
-                        break;
-                    if (currentProperty.type == "FloatRange")
-                    {
-                        m_RangeProperty = currentProperty.Copy();
-                        m_Properties.Add(new FloatRangeElement(m_RangeProperty));
-                    }
-                    else
-                    {
-                        var propertyField = new PropertyField(currentProperty.Copy());
-                        propertyField.Bind(m_Property.serializedObject);
-                        var originalField = m_Sampler.GetType().GetField(currentProperty.name);
-                        var tooltipAttribute = originalField.GetCustomAttributes(true).ToList().Find(att => att.GetType() == typeof(TooltipAttribute));
-                        if (tooltipAttribute != null)
-                        {
-                            propertyField.tooltip = (tooltipAttribute as TooltipAttribute)?.tooltip;
-                        }
-                        m_Properties.Add(propertyField);
-                    }
-                }
-                while (currentProperty.NextVisible(false));
-            }
-        }
+            var displayName = this.Q<Label>("display-name");
+            displayName.text = property.displayName;
-        static string UppercaseFirstLetter(string s)
-        {
-            return string.IsNullOrEmpty(s) ? string.Empty : char.ToUpper(s[0]) + s.Substring(1);
-        }
-
-        ISampler GetSamplerFromSerializedObject()
-        {
-            var configType = m_Parameter.GetType();
-            var field = configType.GetField(m_Property.name);
-            return (ISampler)field.GetValue(m_Parameter);
+            var fieldsContainer = this.Q<VisualElement>("fields-container");
+            UIElementsEditorUtilities.CreatePropertyFields(property, fieldsContainer);
         }
     }
 }

com.unity.perception/Editor/Randomization/VisualElements/Sampler/SamplerElement.cs.meta

-fileFormatVersion: 2
-guid: 134b50014b9f4c0694a087d3529ea4c2
-MonoImporter:
-  externalObjects: {}
-  serializedVersion: 2
-  defaultReferences: []
-  executionOrder: 0
-  icon: {instanceID: 0}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: 
+fileFormatVersion: 2
+guid: a5920440efa84756a581dda95394a14f
+timeCreated: 1612042675

com.unity.perception/Runtime/Randomization/Parameters/CategoricalParameter.cs

         public override void Validate()
         {
             base.Validate();
+
+            // Check for a non-zero amount of specified categories
+
+            // Check for duplicate categories
+            var uniqueCategories = new HashSet<T>();
+            foreach (var option in m_Categories)
+                if (uniqueCategories.Contains(option))
+                    throw new ParameterValidationException("Duplicate categories");
+                else
+                    uniqueCategories.Add(option);
+
+            // Check if the number of specified probabilities is different from the number of listed categories
             if (!uniform)
             {
                 if (probabilities.Count != m_Categories.Count)

com.unity.perception/Runtime/Randomization/Randomizers/Randomizer.cs

         /// <summary>
         /// Enabled Randomizers are updated, disabled Randomizers are not.
         /// </summary>
-        [field: SerializeField] public bool enabled { get; set; } = true;
+        [field: SerializeField, HideInInspector] public bool enabled { get; set; } = true;
 
         /// <summary>
         /// Returns the scenario containing this Randomizer

com.unity.perception/Runtime/Randomization/Samplers/ISampler.cs

 using System;
-using Unity.Collections;
-using Unity.Jobs;
 using UnityEngine;
 
 namespace UnityEngine.Experimental.Perception.Randomization.Samplers

com.unity.perception/Tests/Runtime/Randomization/ParameterTests/CategoricalParameterTests.cs

         public void NegativeProbabilities()
         {
             var parameter = new StringParameter();
-            var optionsArray = new [] { ("option1", 1f), ("option1", -1f) };
+            var optionsArray = new [] { ("option1", 1f), ("option2", -1f) };
+        {
+            var parameter = new StringParameter();
+            var optionsArray = new [] { ("option1", 0f), ("option2", 0f) };
+            Assert.Throws<ParameterValidationException>(() => parameter.SetOptions(optionsArray));
+        }
+
+        [Test]
+        public void DuplicateCategoriesTest()
         {
             var parameter = new StringParameter();
             var optionsArray = new [] { ("option1", 0f), ("option1", 0f) };

com.unity.perception/Editor/Randomization/PropertyDrawers/FloatRangeDrawer.cs

+using System;
+using UnityEngine;
+using UnityEngine.Experimental.Perception.Randomization.Samplers;
+using UnityEngine.UIElements;
+
+namespace UnityEditor.Experimental.Perception.Randomization.PropertyDrawers
+{
+    [CustomPropertyDrawer(typeof(FloatRange))]
+    class FloatRangeDrawer : PropertyDrawer
+    {
+        public override VisualElement CreatePropertyGUI(SerializedProperty property)
+        {
+            return new FloatRangeElement(property);
+        }
+
+        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+        {
+            EditorGUI.PropertyField(position, property, label, true);
+        }
+
+        public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+        {
+            return EditorGUI.GetPropertyHeight(property);
+        }
+    }
+}

com.unity.perception/Editor/Randomization/PropertyDrawers/FloatRangeDrawer.cs.meta

+fileFormatVersion: 2
+guid: 2aaf69aad9c844a592283d36b3c14d8f
+timeCreated: 1612042769

com.unity.perception/Editor/Randomization/PropertyDrawers/SamplerDrawer.cs

+using System;
+using UnityEngine;
+using UnityEngine.Experimental.Perception.Randomization.Samplers;
+using UnityEngine.UIElements;
+
+namespace UnityEditor.Experimental.Perception.Randomization.PropertyDrawers
+{
+    [CustomPropertyDrawer(typeof(ISampler), true)]
+    class SamplerDrawer : PropertyDrawer
+    {
+        public override VisualElement CreatePropertyGUI(SerializedProperty property)
+        {
+            return fieldInfo.FieldType.IsInterface
+                ? new SamplerInterfaceElement(property) as VisualElement
+                : new SamplerElement(property);
+        }
+
+        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+        {
+            EditorGUI.PropertyField(position, property, label, true);
+        }
+
+        public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+        {
+            return EditorGUI.GetPropertyHeight(property);
+        }
+    }
+}

com.unity.perception/Editor/Randomization/PropertyDrawers/SamplerDrawer.cs.meta

+fileFormatVersion: 2
+guid: 87021ed3ca1241f8953af2ee975504c4
+timeCreated: 1612040428

com.unity.perception/Editor/Randomization/Uxml/Sampler/SamplerInterfaceElement.uxml

+<UXML xmlns="UnityEngine.UIElements" xmlns:editor="UnityEditor.UIElements">
+    <VisualElement name="sampler-template" style="margin-bottom: 4px;">
+        <Style src="../../Uss/Styles.uss"/>
+        <VisualElement style="flex-direction: row; align-items: center;">
+            <Label name="sampler-name" text="Sampler Name" class="unity-base-field__label"/>
+            <editor:ToolbarMenu name="sampler-type-dropdown" text="Placeholder Sampler Type" class="sampler__type-menu"/>
+        </VisualElement>
+        <VisualElement name="fields-container" style="margin-left: 18px;"/>
+    </VisualElement>
+</UXML>

com.unity.perception/Editor/Randomization/Uxml/Sampler/SamplerInterfaceElement.uxml.meta

+fileFormatVersion: 2
+guid: e91be9c80e944358b231c125be80a749
+timeCreated: 1594847524

com.unity.perception/Editor/Randomization/VisualElements/Sampler/SamplerInterfaceElement.cs

+using System;
+using UnityEditor.UIElements;
+using UnityEngine.Experimental.Perception.Randomization.Samplers;
+using UnityEngine.UIElements;
+
+namespace UnityEditor.Experimental.Perception.Randomization
+{
+    class SamplerInterfaceElement : VisualElement
+    {
+        VisualElement m_PropertiesContainer;
+        SerializedProperty m_Property;
+        SerializedProperty m_RangeProperty;
+        ToolbarMenu m_SamplerTypeDropdown;
+
+        public SamplerInterfaceElement(SerializedProperty property)
+        {
+            m_Property = property;
+            var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
+                $"{StaticData.uxmlDir}/Sampler/SamplerInterfaceElement.uxml");
+            template.CloneTree(this);
+
+            if (sampler == null)
+                CreateSampler(typeof(UniformSampler));
+
+            var samplerName = this.Q<Label>("sampler-name");
+            samplerName.text = UppercaseFirstLetter(m_Property.name);
+
+            m_PropertiesContainer = this.Q<VisualElement>("fields-container");
+            m_SamplerTypeDropdown = this.Q<ToolbarMenu>("sampler-type-dropdown");
+            m_SamplerTypeDropdown.text = SamplerUtility.GetSamplerDisplayName(sampler.GetType());
+            ;
+            foreach (var samplerType in StaticData.samplerTypes)
+            {
+                var displayName = SamplerUtility.GetSamplerDisplayName(samplerType);
+                ;
+                m_SamplerTypeDropdown.menu.AppendAction(
+                    displayName,
+                    a => { ReplaceSampler(samplerType); },
+                    a => DropdownMenuAction.Status.Normal);
+            }
+
+            CreatePropertyFields();
+        }
+
+        ISampler sampler => (ISampler)StaticData.GetManagedReferenceValue(m_Property);
+
+        void ReplaceSampler(Type samplerType)
+        {
+            CreateSampler(samplerType);
+            m_SamplerTypeDropdown.text = SamplerUtility.GetSamplerDisplayName(samplerType);
+            CreatePropertyFields();
+        }
+
+        void CreateSampler(Type samplerType)
+        {
+            var newSampler = (ISampler)Activator.CreateInstance(samplerType);
+            CopyFloatRangeToNewSampler(newSampler);
+            m_Property.managedReferenceValue = newSampler;
+            m_Property.serializedObject.ApplyModifiedProperties();
+        }
+
+        void CopyFloatRangeToNewSampler(ISampler newSampler)
+        {
+            if (m_RangeProperty == null)
+                return;
+
+            var rangeField = newSampler.GetType().GetField(m_RangeProperty.name);
+            if (rangeField == null)
+                return;
+
+            var range = new FloatRange(
+                m_RangeProperty.FindPropertyRelative("minimum").floatValue,
+                m_RangeProperty.FindPropertyRelative("maximum").floatValue);
+            rangeField.SetValue(newSampler, range);
+        }
+
+        void CreatePropertyFields()
+        {
+            m_RangeProperty = null;
+            m_PropertiesContainer.Clear();
+            UIElementsEditorUtilities.CreatePropertyFields(m_Property, m_PropertiesContainer);
+        }
+
+        static string UppercaseFirstLetter(string s)
+        {
+            return string.IsNullOrEmpty(s) ? string.Empty : char.ToUpper(s[0]) + s.Substring(1);
+        }
+    }
+}

com.unity.perception/Editor/Randomization/VisualElements/Sampler/SamplerInterfaceElement.cs.meta

+fileFormatVersion: 2
+guid: 134b50014b9f4c0694a087d3529ea4c2
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

com.unity.perception/Editor/Randomization/Utilities/ParameterUIElementsEditor.cs

+using System;
+using UnityEngine;
+using UnityEngine.UIElements;
+
+namespace UnityEditor.Experimental.Perception.Randomization
+{
+    /// <summary>
+    /// Derive this class to force the Unity Editor to render the default inspector using UIElements for an Object that
+    /// includes a Parameter field.
+    /// to allow parameter UIs to render properly
+    /// </summary>
+    public abstract class ParameterUIElementsEditor : Editor
+    {
+        ///<inheritdoc/>
+        public override VisualElement CreateInspectorGUI()
+        {
+            var rootElement = new VisualElement();
+            UIElementsEditorUtilities.CreatePropertyFields(serializedObject, rootElement);
+            return rootElement;
+        }
+    }
+}

com.unity.perception/Editor/Randomization/Utilities/StaticData.cs

+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using UnityEngine.Experimental.Perception.Randomization.Randomizers;
+using UnityEngine.Experimental.Perception.Randomization.Samplers;
+
+namespace UnityEditor.Experimental.Perception.Randomization
+{
+    static class StaticData
+    {
+        const string k_RandomizationDir = "Packages/com.unity.perception/Editor/Randomization";
+        internal const string uxmlDir = k_RandomizationDir + "/Uxml";
+
+        internal static Type[] randomizerTypes;
+        internal static Type[] samplerTypes;
+
+        static StaticData()
+        {
+            randomizerTypes = GetConstructableDerivedTypes<Randomizer>();
+            samplerTypes = GetConstructableDerivedTypes<ISampler>();
+        }
+
+        static Type[] GetConstructableDerivedTypes<T>()
+        {
+            var collection = TypeCache.GetTypesDerivedFrom<T>();
+            var types = new List<Type>();
+            foreach (var type in collection)
+                if (!type.IsAbstract && !type.IsInterface)
+                    types.Add(type);
+            return types.ToArray();
+        }
+
+        public static object GetManagedReferenceValue(SerializedProperty prop, bool parent = false)
+        {
+            var path = prop.propertyPath.Replace(".Array.data[", "[");
+            object obj = prop.serializedObject.targetObject;
+            var elements = path.Split('.');
+            if (parent)
+                elements = elements.Take(elements.Count() - 1).ToArray();
+
+            foreach (var element in elements)
+                if (element.Contains("["))
+                {
+                    var elementName = element.Substring(0, element.IndexOf("["));
+                    var index = Convert.ToInt32(element.Substring(element.IndexOf("[")).Replace("[", "").Replace("]", ""));
+                    obj = GetArrayValue(obj, elementName, index);
+                }
+                else
+                {
+                    obj = GetValue(obj, element);
+                }
+
+            return obj;
+        }
+
+        static object GetValue(object source, string name)
+        {
+            if (source == null)
+                return null;
+            var type = source.GetType();
+            var f = type.GetField(name, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
+            if (f == null)
+            {
+                var p = type.GetProperty(name, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase);
+                return p == null ? null : p.GetValue(source, null);
+            }
+
+            return f.GetValue(source);
+        }
+
+        static object GetArrayValue(object source, string name, int index)
+        {
+            var value = GetValue(source, name);
+            if (!(value is IEnumerable enumerable))
+                return null;
+            var enumerator = enumerable.GetEnumerator();
+            while (index-- >= 0)
+                enumerator.MoveNext();
+            return enumerator.Current;
+        }
+
+        public static bool IsSubclassOfRawGeneric(Type generic, Type toCheck)
+        {
+            while (toCheck != null && toCheck != typeof(object))
+            {
+                var cur = toCheck.IsGenericType ? toCheck.GetGenericTypeDefinition() : toCheck;
+                if (generic == cur) return true;
+                toCheck = toCheck.BaseType;
+            }
+            return false;
+        }
+    }
+}

com.unity.perception/Editor/Randomization/Utilities/UIElementsEditorUtilities.cs

+using System;
+using System.Linq;
+using UnityEditor.UIElements;
+using UnityEngine;
+using UnityEngine.UIElements;
+
+namespace UnityEditor.Experimental.Perception.Randomization
+{
+    /// <summary>
+    /// This class contains a set of helper functions for simplifying the creation of UI Elements editors
+    /// </summary>
+    public static class UIElementsEditorUtilities
+    {
+        /// <summary>
+        /// Creates a list of PropertyFields from the class fields of the given SerializedObject
+        /// and adds them to the specified container element
+        /// </summary>
+        /// <param name="serializedObj">The SerializedObject to create property fields for</param>
+        /// <param name="containerElement">The element to place the created PropertyFields in</param>
+        public static void CreatePropertyFields(SerializedObject serializedObj, VisualElement containerElement)
+        {
+            var fieldType = serializedObj.targetObject.GetType();
+            var iterator = serializedObj.GetIterator();
+            iterator.NextVisible(true);
+            iterator.NextVisible(false);
+            do
+            {
+                var propertyField = CreatePropertyField(iterator, fieldType);
+                containerElement.Add(propertyField);
+            } while (iterator.NextVisible(false));
+        }
+
+        /// <summary>
+        /// Creates a list of PropertyFields from the sub-fields of the given SerializedProperty
+        /// and adds them to the specified container element
+        /// </summary>
+        /// <param name="property">The SerializedProperty to create sub property fields for</param>
+        /// <param name="containerElement">The element to place the created PropertyFields in</param>
+        public static void CreatePropertyFields(SerializedProperty property, VisualElement containerElement)
+        {
+            var fieldType = StaticData.GetManagedReferenceValue(property).GetType();
+
+            var iterator = property.Copy();
+            var nextSiblingProperty = property.Copy();
+            nextSiblingProperty.NextVisible(false);
+
+            if (iterator.NextVisible(true))
+                do
+                {
+                    if (SerializedProperty.EqualContents(iterator, nextSiblingProperty))
+                        break;
+                    var propertyField = CreatePropertyField(iterator, fieldType);
+                    containerElement.Add(propertyField);
+                } while (iterator.NextVisible(false));
+        }
+
+        /// <summary>
+        /// Creates a PropertyField from a given SerializedProperty (with tooltips!)
+        /// </summary>
+        /// <param name="iterator">The SerializedProperty to create a PropertyField</param>
+        /// <param name="parentPropertyType">The Type of the class encapsulating the provided SerializedProperty</param>
+        /// <returns></returns>
+        public static PropertyField CreatePropertyField(SerializedProperty iterator, Type parentPropertyType)
+        {
+            var propertyField = new PropertyField(iterator.Copy());
+            propertyField.Bind(iterator.serializedObject);
+            var originalField = parentPropertyType.GetField(iterator.name);
+            var tooltipAttribute = originalField.GetCustomAttributes(true)
+                .ToList().Find(att => att.GetType() == typeof(TooltipAttribute));
+            if (tooltipAttribute != null)
+                propertyField.tooltip = (tooltipAttribute as TooltipAttribute)?.tooltip;
+            return propertyField;
+        }
+    }
+}

com.unity.perception/Editor/Randomization/Utilities/UIElementsEditorUtilities.cs.meta

+fileFormatVersion: 2
+guid: 9ed5513847d3486dbf017c9fb30186b9
+timeCreated: 1612048047

com.unity.perception/Editor/Randomization/StaticData.cs

-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Linq;
-using System.Reflection;
-using UnityEditor;
-using UnityEngine.Experimental.Perception.Randomization.Parameters;
-using UnityEngine.Experimental.Perception.Randomization.Randomizers;
-using UnityEngine.Experimental.Perception.Randomization.Samplers;
-
-namespace UnityEngine.Experimental.Perception.Randomization.Editor
-{
-    static class StaticData
-    {
-        const string k_RandomizationDir = "Packages/com.unity.perception/Editor/Randomization";
-        internal const string uxmlDir = k_RandomizationDir + "/Uxml";
-
-        internal static readonly string samplerSerializedFieldType;
-
-        internal static Type[] randomizerTypes;
-        internal static Type[] samplerTypes;
-
-        static StaticData()
-        {
-            randomizerTypes = GetConstructableDerivedTypes<Randomizer>();
-            samplerTypes = GetConstructableDerivedTypes<ISampler>();
-            var samplerType = typeof(ISampler);
-            samplerSerializedFieldType = $"{samplerType.Assembly.GetName().Name} {samplerType.FullName}";
-        }
-
-        static Type[] GetConstructableDerivedTypes<T>()
-        {
-            var collection = TypeCache.GetTypesDerivedFrom<T>();
-            var types = new List<Type>();
-            foreach (var type in collection)
-            {
-                if (!type.IsAbstract && !type.IsInterface)
-                    types.Add(type);
-            }
-            return types.ToArray();
-        }
-
-        internal static object GetManagedReferenceValue(SerializedProperty prop, bool parent=false)
-        {
-            var path = prop.propertyPath.Replace(".Array.data[", "[");
-            object obj = prop.serializedObject.targetObject;
-            var elements = path.Split('.');
-            if (parent)
-                elements = elements.Take(elements.Count() - 1).ToArray();
-
-            foreach (var element in elements)
-            {
-                if (element.Contains("["))
-                {
-                    var elementName = element.Substring(0, element.IndexOf("["));
-                    var index = Convert.ToInt32(element.Substring(element.IndexOf("[")).Replace("[","").Replace("]",""));
-                    obj = GetArrayValue(obj, elementName, index);
-                }
-                else
-                    obj = GetValue(obj, element);
-            }
-            return obj;
-        }
-
-        static object GetValue(object source, string name)
-        {
-            if (source == null)
-                return null;
-            var type = source.GetType();
-            var f = type.GetField(name, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
-            if (f == null)
-            {
-                var p = type.GetProperty(name, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase);
-                return p == null ? null : p.GetValue(source, null);
-            }
-            return f.GetValue(source);
-        }
-
-        static object GetArrayValue(object source, string name, int index)
-        {
-            var value = GetValue(source, name);
-            if (!(value is IEnumerable enumerable))
-                return null;
-            var enumerator = enumerable.GetEnumerator();
-            while (index-- >= 0)
-                enumerator.MoveNext();
-            return enumerator.Current;
-        }
-
-        public static bool IsSubclassOfRawGeneric(Type generic, Type toCheck) {
-            while (toCheck != null && toCheck != typeof(object)) {
-                var cur = toCheck.IsGenericType ? toCheck.GetGenericTypeDefinition() : toCheck;
-                if (generic == cur) {
-                    return true;
-                }
-                toCheck = toCheck.BaseType;
-            }
-            return false;
-        }
-    }
-}