Add OBJ mesh support to Unity plugin

unity/Editor/Importer/MjImporterWithAssets.cs

@@ -174,7 +174,14 @@ public class MjImporterWithAssets : MjcfImporter {
       throw new Exception(
         $"Trying to import mesh {unsanitizedAssetReferenceName} but {assetPath} already exists.");
     }
+
     AssetDatabase.ImportAsset(assetPath);
+    ModelImporter importer = AssetImporter.GetAtPath(assetPath) as ModelImporter;
+    if (importer != null && !importer.isReadable) {
+      importer.isReadable = true;
+      importer.SaveAndReimport();
+    }
+
     var copiedMesh = AssetDatabase.LoadAssetAtPath<Mesh>(assetPath);
     if (copiedMesh == null) {
       throw new Exception($"Mesh {assetPath} was not imported.");
@@ -283,12 +290,12 @@ public class MjImporterWithAssets : MjcfImporter {
         // We use the geom's name, guaranteed to be unique, as the asset name.
         // If geom is nameless, use a random number.
         var name =
-          MjEngineTool.Sanitize(parentNode.GetStringAttribute(
+            MjEngineTool.Sanitize(parentNode.GetStringAttribute(
-              "name", defaultValue: $"{UnityEngine.Random.Range(0, 1000000)}"));
+                "name", defaultValue: $"{UnityEngine.Random.Range(0, 1000000)}"));
-        var assetPath = Path.Combine(_targetAssetDir, name + ".mat");
+        var assetPath = Path.Combine(_targetAssetDir, name+".mat");
         if (AssetDatabase.LoadMainAssetAtPath(assetPath) != null) {
           throw new Exception(
-            $"Creating a material asset for the geom {name}, but {assetPath} already exists.");
+              $"Creating a material asset for the geom {name}, but {assetPath} already exists.");
         }
         AssetDatabase.CreateAsset(material, assetPath);
         AssetDatabase.SaveAssets();
@@ -297,6 +304,7 @@ public class MjImporterWithAssets : MjcfImporter {
         material = DefaultMujocoMaterial;
       }
     }
+    if (parentNode.GetFloatAttribute("group") > 2) renderer.enabled = false;
     renderer.sharedMaterial = material;
   }
 }

unity/Editor/Importer/ObjMeshImportUtility.cs

@@ -11,84 +11,85 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+
 using System;
 using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Text;
+using UnityEditor;
 using UnityEngine;
 
 namespace Mujoco {
 
-  /// <summary>
+/// <summary>
-  /// Scale vertex data manually line by line. We skip normals. Parameter vertex points
+/// Scale vertex data manually line by line. We skip normals. Warning: Parameter vertex points
-  /// (`vp`) was unclear to me how to properly scale them, if you use them and notice an
+/// (`vp`) were unclear to me how to handle with scaling, if you use them and notice an issue
-  /// issue please report it.
+/// please report it.
-  /// </summary>
+/// </summary>
-  public static class ObjMeshImportUtility {
+public static class ObjMeshImportUtility {
-    private static Vector3 ToXZY(float x, float y, float z) => new Vector3(x, z, y);
+  private static Vector3 ToXZY(float x, float y, float z) => new Vector3(x, z, y);
 
-    public static void CopyAndScaleOBJFile(string sourceFilePath, string targetFilePath,
+  public static void CopyAndScaleOBJFile(string sourceFilePath, string targetFilePath,
-        Vector3 scale, bool flipFaces=false) {
+      Vector3 scale) {
-      // OBJ files are human readable
+    // OBJ files are human readable
-      string[] lines = File.ReadAllLines(sourceFilePath);
+    string[] lines = File.ReadAllLines(sourceFilePath);
-      StringBuilder outputBuilder = new StringBuilder();
+    StringBuilder outputBuilder = new StringBuilder();
-      // Culture info for consistent decimal point handling
+    // Culture info for consistent decimal point handling
-      CultureInfo invariantCulture = CultureInfo.InvariantCulture;
+    CultureInfo invariantCulture = CultureInfo.InvariantCulture;
+    scale = ToXZY(scale.x, scale.y, scale.z);
+    foreach (string line in lines) {
+      if (line.StartsWith("v ")) // Vertex line
+      {
+        // Split the line into components
+        string[] parts = line.Split(' ');
+        if (parts.Length >= 4) {
+          // Scale the vertex. It is unclear to me why flipping along x axis was necessary,
+          // but without it meshes were incorrectly oriented.
+          float x = -float.Parse(parts[1], invariantCulture) * scale.x;
+          float y = float.Parse(parts[2], invariantCulture) * scale.y;
+          float z = float.Parse(parts[3], invariantCulture) * scale.z;
 
-      scale = ToXZY(scale.x, scale.y, scale.z);
+          var swizzled = ToXZY(x, y, z);
-      foreach (string line in lines) {
+          outputBuilder.AppendLine(
-        if (line.StartsWith("v ")) // Vertex line
+              $"v {swizzled.x.ToString(invariantCulture)} "+
-        {
+              $"{swizzled.y.ToString(invariantCulture)} "+
-          // Split the line into components
+              $"{swizzled.z.ToString(invariantCulture)}");
-          string[] parts = line.Split(' ');
-          if (parts.Length >= 4) {
-            // Scale the vertex
-            float x = -float.Parse(parts[1], invariantCulture) * scale.x;
-            float y = float.Parse(parts[2], invariantCulture) * scale.y;
-            float z = float.Parse(parts[3], invariantCulture) * scale.z;
-
-            var swizzled = ToXZY(x, y, z);
-            outputBuilder.AppendLine(
-                $"v {swizzled.x.ToString(invariantCulture)} {swizzled.y.ToString(invariantCulture)} {swizzled.z.ToString(invariantCulture)}");
-          }
-        } else if (line.StartsWith("vn ")) {
-          string[] parts = line.Split(' ');
-          if (parts.Length >= 4) {
-            float x = -float.Parse(parts[1], invariantCulture);
-            float y = float.Parse(parts[2], invariantCulture);
-            float z = float.Parse(parts[3], invariantCulture);
-
-            var swizzled = ToXZY(x, y, z);
-            outputBuilder.AppendLine(
-                $"vn {swizzled.x.ToString(invariantCulture)} {swizzled.y.ToString(invariantCulture)} {swizzled.z.ToString(invariantCulture)}");
-          }
-        } else if (line.StartsWith("f ") && flipFaces) {
-          string[] parts = line.Split(' ');
-          if (parts.Length >= 4) {
-            outputBuilder.Append(parts[0] + " ");
-
-            // Apply same vertex order as STL parser: [0,2,1]
-            var face = parts.Skip(1).ToArray();
-            if (face.Length >= 3) {
-              outputBuilder.Append(face[0] + " ");  // vertex 0
-              outputBuilder.Append(face[2] + " ");  // vertex 2
-              outputBuilder.Append(face[1]);        // vertex 1
-
-              // Append any remaining vertices in original order
-              for (int i = 3; i < face.Length; i++) {
-                outputBuilder.Append(" " + face[i]);
-              }
-            }
-            outputBuilder.AppendLine();
-          }
-        } else {
-          // Copy non-vertex lines as-is
-          outputBuilder.AppendLine(line);
         }
+      } else if (line.StartsWith("vn ")) {
+        // We swizzle the normals too
+        string[] parts = line.Split(' ');
+        if (parts.Length >= 4) {
+          float x = -float.Parse(parts[1], invariantCulture);
+          float y = float.Parse(parts[2], invariantCulture);
+          float z = float.Parse(parts[3], invariantCulture);
+
+          var swizzled = ToXZY(x, y, z);
+          outputBuilder.AppendLine(
+              $"vn {swizzled.x.ToString(invariantCulture)} "+
+              $"{swizzled.y.ToString(invariantCulture)} "+
+              $"{swizzled.z.ToString(invariantCulture)}");
+        }
+      } else if (line.StartsWith("f ") && scale.x*scale.y*scale.z < 0) {
+        // Faces definition, flip face by reordering vertices
+        string[] parts = line.Split(' ');
+        if (parts.Length >= 4) {
+          outputBuilder.Append(parts[0]+" ");
+          var face = parts.Skip(1).ToArray();
+          if (face.Length >= 3) {
+            outputBuilder.Append(face[0]+" ");
+            outputBuilder.Append(face[2]+" ");
+            outputBuilder.Append(face[1]);
+          }
+          outputBuilder.AppendLine();
+        }
+      } else {
+        // Copy non-vertex lines as-is
+        outputBuilder.AppendLine(line);
       }
-      // Write the scaled OBJ to the target file
-      File.WriteAllText(targetFilePath, outputBuilder.ToString());
     }
+    // Write the scaled OBJ to the target file
+    File.WriteAllText(targetFilePath, outputBuilder.ToString());
   }
+}
 }

unity/Editor/Importer/ObjMeshImportUtility.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: adec9978c00bb934eb8bf974c26193e1
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

unity/Runtime/Components/Shapes/MjMeshFilter.cs

@@ -41,19 +41,19 @@ public class MjMeshFilter : MonoBehaviour {
       return;
     }
 
-    _shapeChangeStamp = currentChangeStamp;
-    Tuple<Vector3[], int[]> meshData = _geom.BuildMesh();
-
-    if (meshData == null) {
-      throw new ArgumentException("Unsupported geom shape detected");
-    }
-
     if(_geom.ShapeType == MjShapeComponent.ShapeTypes.Mesh) { 
       MjMeshShape meshShape = _geom.Shape as MjMeshShape;
       _meshFilter.sharedMesh = meshShape.Mesh;
       return;
     }
 
+    _shapeChangeStamp = currentChangeStamp;
+    Tuple<Vector3[], int[]> meshData = _geom.BuildMesh();
+    if (meshData == null)
+    {
+      throw new ArgumentException("Unsupported geom shape detected");
+    }
+
     DisposeCurrentMesh();
 
     var mesh = new Mesh();