Do not render flexes/skins with no geometry.

PiperOrigin-RevId: 933604372
Change-Id: I80169ff09ec6908d101b5f10bbf8aa1a6e8b8249

src/experimental/filament/compat/scene_bridge.cc

@@ -126,8 +126,10 @@ void SceneBridge::Update(const mjrRect& viewport, const mjvScene* scene) {
     }
 
     if (geom->type == mjGEOM_FLEX || geom->type == mjGEOM_SKIN) {
-      scene_objects_->CreateSkinFlexMesh(scene, model_objects_->GetModel(),
+      if (!scene_objects_->CreateSkinFlexMesh(scene, model_objects_->GetModel(),
-                                         *geom);
+                                              *geom)) {
+        continue;
+      }
     }
 
     UniquePtr<mjrfRenderable> renderable = CreateGeomRenderable(

src/experimental/filament/compat/scene_objects.cc

@@ -103,9 +103,13 @@ static std::span<const int> GetIndices(const mjModel* model,
   }
 }
 
-static void UpdateSkinFlexMeshData(mjrfMeshData* data, const mjModel* model,
+static bool UpdateSkinFlexMeshData(mjrfMeshData* data, const mjModel* model,
                                    const mjvScene* scene, const mjvGeom& geom) {
   auto positions = GetPositions(model, scene, geom);
+  if (positions.empty()) {
+    return false;
+  }
+
   auto normals = GetNormals(model, scene, geom);
   auto uvs = GetUvs(model, scene, geom);
   auto indices = GetIndices(model, scene, geom);
@@ -133,16 +137,19 @@ static void UpdateSkinFlexMeshData(mjrfMeshData* data, const mjModel* model,
   data->compute_bounds = true;
   data->release = nullptr;
   data->user_data = nullptr;
+  return true;
 }
 
 SceneObjects::SceneObjects(mjrfContext* ctx) : ctx_(ctx) {}
 
-void SceneObjects::CreateSkinFlexMesh(const mjvScene* scene,
+bool SceneObjects::CreateSkinFlexMesh(const mjvScene* scene,
                                       const mjModel* model,
                                       const mjvGeom& geom) {
   mjrfMeshData data;
   mjrf_defaultMeshData(&data);
-  UpdateSkinFlexMeshData(&data, model, scene, geom);
+  if (!UpdateSkinFlexMeshData(&data, model, scene, geom)) {
+    return false;
+  }
   if (geom.type == mjGEOM_FLEX) {
     flexes_.insert_or_assign(geom.objid, CreateMesh(ctx_, data));
   } else if (geom.type == mjGEOM_SKIN) {
@@ -150,6 +157,7 @@ void SceneObjects::CreateSkinFlexMesh(const mjvScene* scene,
   } else {
     mju_error("Unsupported dynamic mesh type: %d", geom.type);
   }
+  return true;
 }
 
 const mjrfMesh* SceneObjects::GetFlexMesh(int geom_id) const {

src/experimental/filament/compat/scene_objects.h

@@ -30,7 +30,7 @@ class SceneObjects {
   explicit SceneObjects(mjrfContext* ctx);
 
   // Creates a skin or flex mesh from the given geom in the mjvScene.
-  void CreateSkinFlexMesh(const mjvScene* scene, const mjModel* model,
+  bool CreateSkinFlexMesh(const mjvScene* scene, const mjModel* model,
                           const mjvGeom& geom);
 
   // Returns the mesh for the given geom id, as created by CreateSkinFlexMesh.