Allow mocap bodies to be loaded by the Unity plugin.

PiperOrigin-RevId: 558735711
Change-Id: Ibc9a81cbf8ec4b979d5b325c822c1bffc1408509

unity/Runtime/Components/Bodies/MjMocapBody.cs

@@ -19,7 +19,11 @@ using UnityEngine;
 namespace Mujoco {
   public class MjMocapBody : MjBaseBody {
     protected override void OnParseMjcf(XmlElement mjcf) {
-      throw new Exception("parsing mocap bodies isn't supported.");
+      // Transform
+      transform.localPosition =
+          MjEngineTool.UnityVector3(mjcf.GetVector3Attribute("pos", defaultValue: Vector3.zero));
+      transform.localRotation = MjEngineTool.UnityQuaternion(
+          mjcf.GetQuaternionAttribute("quat", defaultValue: MjEngineTool.MjQuaternionIdentity));
     }
 
     protected override unsafe void OnBindToRuntime(MujocoLib.mjModel_* model, MujocoLib.mjData_* data) {

unity/Runtime/Components/Sensors/MjBodyQuaternionSensor.cs

@@ -20,7 +20,7 @@ using UnityEngine;
 namespace Mujoco {
 
 public class MjBodyQuaternionSensor : MjBaseSensor {
-  public MjBody Body;
+  public MjBaseBody Body;
 
   [Tooltip("Should the Frame sensors use the inertial or the regular frame of reference.")]
   public bool UseInertialFrame;
@@ -39,7 +39,7 @@ public class MjBodyQuaternionSensor : MjBaseSensor {
 
   protected override void FromMjcf(XmlElement mjcf) {
     UseInertialFrame = mjcf.HasAttribute("body");
-    Body = mjcf.GetObjectReferenceAttribute<MjBody>("objname");
+    Body = mjcf.GetObjectReferenceAttribute<MjBaseBody>("objname");
     if (Body == null) {
       throw new NullReferenceException("Missing a reference to a MjBody.");
     }

unity/Runtime/Components/Sensors/MjBodyVectorSensor.cs

@@ -36,7 +36,7 @@ public class MjBodyVectorSensor : MjBaseSensor {
     FrameAngAcc,
   }
   public AvailableSensors SensorType;
-  public MjBody Body;
+  public MjBaseBody Body;
 
   [Tooltip("Should the Frame sensors use the inertial or the regular frame of reference.")]
   public bool UseInertialFrame;
@@ -64,9 +64,9 @@ public class MjBodyVectorSensor : MjBaseSensor {
     }
     if (mjcf.Name.Contains("frame")) {
       UseInertialFrame = mjcf.HasAttribute("body"); // as opposed to xbody
-      Body = mjcf.GetObjectReferenceAttribute<MjBody>("objname");
+      Body = mjcf.GetObjectReferenceAttribute<MjBaseBody>("objname");
     } else {
-      Body = mjcf.GetObjectReferenceAttribute<MjBody>("body");
+      Body = mjcf.GetObjectReferenceAttribute<MjBaseBody>("body");
     }
   }
 

unity/Runtime/Importer/MjcfImporter.cs

@@ -252,7 +252,18 @@ public class MjcfImporter {
         break;
       }
       case "body": {
-        var childObject = CreateGameObjectWithUniqueName<MjBody>(parentObject, child);
+        GameObject childObject = null;
+        const string mocapAttribute = "mocap";
+        if (child.HasAttribute(mocapAttribute)) {
+          var mocapValueStr = child.GetAttribute(mocapAttribute);
+          var mocapValue = bool.Parse(mocapValueStr);
+          if (mocapValue) {
+            childObject = CreateGameObjectWithUniqueName<MjMocapBody>(parentObject, child);
+          }
+        }
+        if (childObject == null) {
+          childObject = CreateGameObjectWithUniqueName<MjBody>(parentObject, child);
+        }
         ParseBodyChildren(childObject, child);
         break;
       }