Allow submeshes to be set when adding meshes to a Renderable.

Also add support for blend order.

PiperOrigin-RevId: 900061778
Change-Id: I601757a8672fed23e45defd4cdbe4e9526ea3b70

src/experimental/filament/filament/renderable.cc

@@ -31,11 +31,11 @@ Renderable::Renderable(filament::Engine* engine) : material_(engine) {}
 
 Renderable::~Renderable() noexcept {
   while (!entities_.empty()) {
-    RemoveLast();
+    RemoveLastEntity();
   }
 }
 
-void Renderable::RemoveLast() {
+void Renderable::RemoveLastEntity() {
   if (entities_.empty()) {
     return;
   }
@@ -53,37 +53,32 @@ void Renderable::RemoveLast() {
   meshes_.pop_back();
 }
 
-void Renderable::Update(int index, const Mesh* mesh) {
-  if (index < 0 || index >= entities_.size()) {
-    mju_error("Invalid index %d for renderable.", index);
-  }
-  utils::Entity& entity = entities_[index];
-  UpdateEntity(entity, mesh);
-  UpdateMeshes(index, mesh);
+void Renderable::UpdateMesh(int index, const Mesh* mesh, int elem_offset,
+                            int elem_count) {
+  MeshInfo& mesh_info = SetMesh(index, mesh, nullptr, elem_offset, elem_count);
+  UpdateEntity(index, mesh_info);
 }
 
-void Renderable::Update(int index, MeshPtr mesh) {
-  if (index < 0 || index >= entities_.size()) {
-    mju_error("Invalid index %d for renderable.", index);
-  }
-  utils::Entity& entity = entities_[index];
-  UpdateEntity(entity, mesh.get());
-  UpdateMeshes(index, mesh.get(), std::move(mesh));
+void Renderable::UpdateMesh(int index, MeshPtr mesh, int elem_offset,
+                            int elem_count) {
+  MeshInfo& mesh_info =
+      SetMesh(index, mesh.get(), std::move(mesh), elem_offset, elem_count);
+  UpdateEntity(index, mesh_info);
 }
 
-void Renderable::Append(const Mesh* mesh) {
-  utils::Entity entity = CreateEntity(mesh);
-  entities_.push_back(entity);
-  meshes_.push_back({nullptr, mesh});
+void Renderable::AppendMesh(const Mesh* mesh, int elem_offset, int elem_count) {
+  MeshInfo& mesh_info = SetMesh(-1, mesh, nullptr, elem_offset, elem_count);
+  AppendEntity(mesh_info);
 }
 
-void Renderable::Append(MeshPtr mesh) {
-  utils::Entity entity = CreateEntity(mesh.get());
-  entities_.push_back(entity);
-  meshes_.push_back({std::move(mesh), mesh.get()});
+void Renderable::AppendMesh(MeshPtr mesh, int elem_offset, int elem_count) {
+  MeshInfo& mesh_info =
+      SetMesh(-1, mesh.get(), std::move(mesh), elem_offset, elem_count);
+  AppendEntity(mesh_info);
 }
 
-utils::Entity Renderable::CreateEntity(const Mesh* mesh) {
+void Renderable::AppendEntity(const MeshInfo& mesh_info) {
+  const Mesh* mesh = mesh_info.mesh;
   filament::VertexBuffer* vertex_buffer = mesh->GetFilamentVertexBuffer();
   if (vertex_buffer == nullptr) {
     mju_error("Invalid (null) vertex buffer.");
@@ -100,7 +95,8 @@ utils::Entity Renderable::CreateEntity(const Mesh* mesh) {
   }
 
   filament::RenderableManager::Builder builder(1);
-  builder.geometry(0, mesh->GetPrimitiveType(), vertex_buffer, index_buffer);
+  builder.geometry(0, mesh->GetPrimitiveType(), vertex_buffer, index_buffer,
+                   mesh_info.elem_offset, mesh_info.elem_count);
   if (mesh->HasBounds()) {
     builder.boundingBox(mesh->GetBounds());
   } else {
@@ -113,17 +109,23 @@ utils::Entity Renderable::CreateEntity(const Mesh* mesh) {
   builder.receiveShadows(receive_shadows_);
   builder.layerMask(0xff, layer_mask_);
   builder.priority(priority_);
+  builder.blendOrder(0, blend_order_);
   builder.screenSpaceContactShadows(true);
-  ;
 
   builder.build(*GetEngine(), entity);
   if (assigned_scene_) {
     assigned_scene_->addEntity(entity);
   }
-  return entity;
+  entities_.push_back(entity);
 }
 
-void Renderable::UpdateEntity(utils::Entity entity, const Mesh* mesh) {
+void Renderable::UpdateEntity(int index, const MeshInfo& mesh_info) {
+  if (index < 0 || index >= entities_.size()) {
+    mju_error("Invalid index %d for renderable.", index);
+  }
+  utils::Entity entity = entities_[index];
+
+  const Mesh* mesh = mesh_info.mesh;
   filament::VertexBuffer* vertex_buffer = mesh->GetFilamentVertexBuffer();
   if (vertex_buffer == nullptr) {
     mju_error("Invalid (null) vertex buffer.");
@@ -136,16 +138,32 @@ void Renderable::UpdateEntity(utils::Entity entity, const Mesh* mesh) {
 
   filament::RenderableManager& rm = GetEngine()->getRenderableManager();
   rm.setGeometryAt(rm.getInstance(entity), 0, mesh->GetPrimitiveType(),
-                   vertex_buffer, index_buffer, 0,
-                   index_buffer->getIndexCount());
+                   vertex_buffer, index_buffer, mesh_info.elem_offset,
+                   mesh_info.elem_count);
 }
 
-void Renderable::UpdateMeshes(int index, const Mesh* mesh, MeshPtr owned_mesh) {
-  if (index < 0 || index >= meshes_.size()) {
+Renderable::MeshInfo& Renderable::SetMesh(int index, const Mesh* mesh,
+                                          MeshPtr owned_mesh, int elem_offset,
+                                          int elem_count) {
+  if (index == -1) {
+    index = meshes_.size();
+    meshes_.emplace_back();
+  }
+  if (index < 0 || index >= static_cast<int>(meshes_.size())) {
     mju_error("Invalid index %d for renderable.", index);
   }
-  meshes_[index].owned_mesh = std::move(owned_mesh);
-  meshes_[index].mesh = mesh;
+
+  MeshInfo* mesh_info = &meshes_[index];
+  mesh_info->owned_mesh = std::move(owned_mesh);
+  mesh_info->mesh = mesh;
+  mesh_info->elem_offset = elem_offset;
+  mesh_info->elem_count = elem_count;
+  if (mesh_info->elem_count == 0) {
+    const int total =
+        mesh_info->mesh->GetFilamentIndexBuffer()->getIndexCount();
+    mesh_info->elem_count = total - mesh_info->elem_offset;
+  }
+  return *mesh_info;
 }
 
 void Renderable::AddToScene(filament::Scene* scene) {
@@ -209,6 +227,19 @@ std::uint8_t Renderable::SetPriority(std::uint8_t priority) {
   return prev;
 }
 
+std::uint16_t Renderable::SetBlendOrder(std::uint16_t blend_order) {
+  std::uint16_t prev = blend_order_;
+  if (blend_order != blend_order_) {
+    blend_order_ = blend_order;
+
+    filament::RenderableManager& rm = GetEngine()->getRenderableManager();
+    for (utils::Entity& entity : entities_) {
+      rm.setBlendOrderAt(rm.getInstance(entity), 0, blend_order_);
+    }
+  }
+  return prev;
+}
+
 void Renderable::SetCastShadows(bool cast_shadows) {
   if (cast_shadows_ != cast_shadows) {
     cast_shadows_ = cast_shadows;
@@ -246,8 +277,8 @@ void Renderable::SetWireframe(bool wireframe) {
       filament::IndexBuffer* index_buffer = mesh->GetFilamentIndexBuffer();
       rm.setGeometryAt(rm.getInstance(entity), 0,
                        wireframe_ ? kWireframeType : mesh->GetPrimitiveType(),
-                       vertex_buffer, index_buffer, 0,
-                       index_buffer->getIndexCount());
+                       vertex_buffer, index_buffer, meshes_[i].elem_offset,
+                       meshes_[i].elem_count);
     }
   }
 }

src/experimental/filament/filament/renderable.h

@@ -26,7 +26,14 @@
 
 namespace mujoco {
 
-// Manages a collection of related filament Renderable Entities.
+// A collection of meshes and a material that, together, define an object that
+// can be rendered in a scene.
+//
+// Meshes can be added to the Renderable either by unique_ptr or raw pointer.
+// This determines whether or not the Renderable takes ownership of the mesh.
+//
+// Internally, the Renderable creates a filament::Entity for each mesh and
+// assigns the same material instance to all of them.
 class Renderable {
  public:
   // Default filament values for priority and layer mask.
@@ -39,42 +46,51 @@ class Renderable {
   Renderable(const Renderable&) = delete;
   Renderable& operator=(const Renderable&) = delete;
 
-  // Appends a new renderable entity built from the given mesh.
-  void Append(const Mesh* mesh);
-  void Append(MeshPtr mesh);
+  // Appends a mesh to the renderable. The elem_offset and elem_count parameters
+  // can be used to specify a submesh to append. If elem_count is 0, assumes
+  // the entire mesh should be appended.
+  void AppendMesh(const Mesh* mesh, int elem_offset = 0, int elem_count = 0);
+  void AppendMesh(MeshPtr mesh, int elem_offset = 0, int elem_count = 0);
 
-  // Updates the entity at the index with new mesh.
-  void Update(int index, const Mesh* mesh);
-  void Update(int index, MeshPtr mesh);
+  // Replaces the mesh at the index with a new mesh. The elem_offset and
+  // elem_count parameters can be used to specify a submesh to append. If
+  // elem_count is 0, assumes the entire mesh should be appended.
+  void UpdateMesh(int index, const Mesh* mesh, int elem_offset = 0,
+              int elem_count = 0);
+  void UpdateMesh(int index, MeshPtr mesh, int elem_offset = 0,
+                  int elem_count = 0);
 
-  // Removes the last entity.
-  void RemoveLast();
+  // Returns the number of meshes that define the renderable.
+  int GetNumMeshes() const { return meshes_.size(); }
 
-  // Returns the entity at the given index.
-  utils::Entity operator[](int index) { return entities_[index]; }
-
-  // Returns the number of Entities that make up this renderable.
-  int GetNumEntities() const { return entities_.size(); }
-
-  // Hides all managed entities.
+  // Sets the layer mask for the managed filament Entities. Layer masks can be
+  // used to show/hide the renderable in different views. Returns the previous
+  // layer mask.
   std::uint8_t SetLayerMask(std::uint8_t mask);
 
-  // Sets the priority of all managed entities.
+  // Sets the priority for the managed filament Entities. The priority
+  // determines the order in which renderables are rendered. Returns the
+  // previous priority.
   std::uint8_t SetPriority(std::uint8_t priority);
 
-  // Disables the renderables from casting shadows.
+  // Sets the blend order of the managed filament entities. This determines the
+  // order in which renderables are blended together. Returns the previous blend
+  // order.
+  std::uint16_t SetBlendOrder(std::uint16_t blend_order);
+
+  // Disables the renderable from casting shadows.
   void SetCastShadows(bool cast_shadows);
 
-  // Disables the renderables from receiving shadows.
+  // Disables the renderable from receiving shadows.
   void SetReceiveShadows(bool receive_shadows);
 
-  // If true, forces all entities to be rendered as lines.
+  // If true, forces all meshes to be rendered using Lines primitives.
   void SetWireframe(bool wireframe);
 
-  // Adds all managed entities to the given filament Scene.
+  // Adds the renderable to the given filament Scene.
   void AddToScene(filament::Scene* scene);
 
-  // Removes all managed entities from the given filament Scene.
+  // Removes the renderable from the given filament Scene.
   void RemoveFromScene(filament::Scene* scene);
 
   // Sets the material instance for all managed entities.
@@ -86,23 +102,40 @@ class Renderable {
   // Returns the filament Engine managing the renderables.
   filament::Engine* GetEngine();
 
- private:
-  utils::Entity CreateEntity(const Mesh* mesh);
-  void UpdateEntity(utils::Entity entity, const Mesh* mesh);
-  void UpdateMeshes(int index, const Mesh* mesh, MeshPtr owned_mesh = nullptr);
+  // Returns the underlying filament::entity for the given mesh.
+  utils::Entity operator[](int index) { return entities_[index]; }
 
-  struct MeshWrapper {
+ private:
+  struct MeshInfo {
     MeshPtr owned_mesh;
     const Mesh* mesh = nullptr;
+    int elem_offset = 0;
+    int elem_count = 0;
   };
 
+  // Sets the mesh information for the mesh at the given index. If index is -1,
+  // a new mesh will be appended to the renderable.
+  MeshInfo& SetMesh(int index, const Mesh* mesh, MeshPtr owned_mesh,
+                    int elem_offset, int elem_count);
+
+  // Appends a new filament::Entity to the renderable, configured to use the
+  // given mesh.
+  void AppendEntity(const MeshInfo& mesh_info);
+
+  // Updates the filament::Entity at the given index to use the given mesh.
+  void UpdateEntity(int index, const MeshInfo& mesh_info);
+
+  // Removes the last filament::Entity from the renderable.
+  void RemoveLastEntity();
+
   Material material_;
   filament::Scene* assigned_scene_ = nullptr;
   filament::MaterialInstance* material_instance_ = nullptr;
   std::vector<utils::Entity> entities_;
-  std::vector<MeshWrapper> meshes_;
+  std::vector<MeshInfo> meshes_;
   std::uint8_t priority_ = kDefaultPriority;
   std::uint8_t layer_mask_ = kDefaultLayerMask;
+  std::uint16_t blend_order_ = 0;
   bool wireframe_ = false;
   bool cast_shadows_ = true;
   bool receive_shadows_ = true;

src/experimental/filament/filament/scene_geom_util.cc

@@ -93,15 +93,15 @@ static void AddMesh(Renderable& renderable, ModelObjects* model_objs,
   if (mesh == nullptr) {
     mju_error("Unknown mesh %d", data_id);
   }
-  renderable.Append(mesh);
+  renderable.AppendMesh(mesh);
 }
 
 static void AddGeom(Renderable& renderable, ModelObjects* model_objs,
                     const mjvScene* scene, const mjvGeom& geom) {
   if (geom.type == mjGEOM_FLEX) {
-    renderable.Append(model_objs->CreateFlexMesh(scene, geom));
+    renderable.AppendMesh(model_objs->CreateFlexMesh(scene, geom));
   } else if (geom.type == mjGEOM_SKIN) {
-    renderable.Append(model_objs->CreateSkinMesh(scene, geom));
+    renderable.AppendMesh(model_objs->CreateSkinMesh(scene, geom));
   }
 }
 
@@ -111,7 +111,7 @@ static void AddHeightField(Renderable& renderable, ModelObjects* model_objs,
   if (mesh == nullptr) {
     mju_error("Unknown height field %d", hfield_id);
   }
-  renderable.Append(mesh);
+  renderable.AppendMesh(mesh);
 }
 
 static void AddShape(Renderable& renderable, ModelObjects* model_objs,
@@ -120,7 +120,7 @@ static void AddShape(Renderable& renderable, ModelObjects* model_objs,
   if (mesh == nullptr) {
     mju_error("Unknown shape %d", shape_type);
   }
-  renderable.Append(mesh);
+  renderable.AppendMesh(mesh);
 }
 
 static void PrepareGeomMeshes(Renderable& renderable, const mjvGeom& geom,
@@ -211,7 +211,7 @@ static void SetGeomTransform(Renderable& renderable, const mjvGeom& geom) {
   float3 size = ReadFloat3(geom.size);
   filament::TransformManager& tm =
       renderable.GetEngine()->getTransformManager();
-  for (int j = 0; j < renderable.GetNumEntities(); ++j) {
+  for (int j = 0; j < renderable.GetNumMeshes(); ++j) {
     const utils::Entity& entity = renderable[j];
 
     // Update object transform.