Merge pull request #4733 from Unity-Technologies/gc-food-goals

Adds goal signal to GridWorld environment

Project/Assets/ML-Agents/Examples/GridWorld/Prefabs/Area.prefab

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+  MaxStep: 100
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Project/Assets/ML-Agents/Examples/GridWorld/Scenes/GridWorld.unity

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Project/Assets/ML-Agents/Examples/GridWorld/Scripts/GridAgent.cs

 using UnityEngine;
 using System.Linq;
 using Unity.MLAgents;
+using Unity.MLAgents.Sensors;
 using Unity.MLAgents.Actuators;
 using UnityEngine.Serialization;
 
         "masking turned on may not behave optimally when action masking is turned off.")]
     public bool maskActions = true;
 
+
+    public GridGoal gridGoal;
+
     const int k_NoAction = 0;  // do nothing!
     const int k_Up = 1;
     const int k_Down = 2;
+    public enum GridGoal
+    {
+        Plus,
+        Cross,
+    }
+
+    }
+
+    public override void CollectObservations(VectorSensor sensor)
+    {
+        Array values = Enum.GetValues(typeof(GridGoal));
+        int goalNum = (int)gridGoal;
+        sensor.AddOneHotObservation(goalNum, values.Length);
     }
 
     public override void WriteDiscreteActionMask(IDiscreteActionMask actionMask)
         }
     }
 
+    private void ProvideReward(GridGoal hitObject)
+    {
+        if (gridGoal == hitObject)
+        {
+            SetReward(1f);
+        }
+        else
+        {
+            SetReward(-1f);
+        }
+    }
+
     // to be implemented by the developer
     public override void OnActionReceived(ActionBuffers actionBuffers)
 
 
             if (hit.Where(col => col.gameObject.CompareTag("goal")).ToArray().Length == 1)
             {
-                SetReward(1f);
+                ProvideReward(GridGoal.Plus);
-                SetReward(-1f);
+                ProvideReward(GridGoal.Cross);
                 EndEpisode();
             }
         }
     public override void OnEpisodeBegin()
     {
         area.AreaReset();
+        Array values = Enum.GetValues(typeof(GridGoal));
+        gridGoal = (GridGoal)values.GetValue(UnityEngine.Random.Range(0, values.Length));
     }
 
     public void FixedUpdate()