updated and fixed the categorical parameter UI

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
+
 ### Changed
 
 Randomizers now access their parent scenario through the static activeScenario property
 
 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
+
+Categorical Parameters no longer error when deleting items from long options lists
 
 
 ## [0.6.0-preview.1] - 2020-12-03

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

         {
             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);
 

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

             {
                 probabilitiesProperty.arraySize++;
                 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 uniformToggle = template.Q<Toggle>("uniform");
             var uniformProperty = m_SerializedProperty.FindPropertyRelative("uniform");
             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);
         }

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/Tests/Runtime/Randomization/ParameterTests/CategoricalParameterTests.cs

 using NUnit.Framework;
 using UnityEngine;
+using UnityEngine.Experimental.Perception.Editor;
 using UnityEngine.Experimental.Perception.Randomization.Parameters;
 
 namespace RandomizationTests.ParameterTests
         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) };