[Impeller Scene] Node deserialization (flutter#38190)

* [Impeller Scene] Node deserialization

* Address comments

* Always use RGBA for the placeholder texture

* Fix node child update

* Temporarily disable test for GLES

* Remove GLES test skip

impeller/scene/geometry.cc

@@ -40,7 +40,7 @@ std::shared_ptr<VertexBufferGeometry> Geometry::MakeVertexBuffer(
   return result;
 }
 
-std::shared_ptr<VertexBufferGeometry> Geometry::MakeFromFBMeshPrimitive(
+std::shared_ptr<VertexBufferGeometry> Geometry::MakeFromFlatbuffer(
     const fb::MeshPrimitive& mesh,
     Allocator& allocator) {
   IndexType index_type;

impeller/scene/geometry.h

@@ -28,7 +28,7 @@ class Geometry {
   static std::shared_ptr<VertexBufferGeometry> MakeVertexBuffer(
       VertexBuffer vertex_buffer);
 
-  static std::shared_ptr<VertexBufferGeometry> MakeFromFBMeshPrimitive(
+  static std::shared_ptr<VertexBufferGeometry> MakeFromFlatbuffer(
       const fb::MeshPrimitive& mesh,
       Allocator& allocator);
 

impeller/scene/material.cc

@@ -18,6 +18,8 @@ namespace scene {
 /// Material
 ///
 
+Material::~Material() = default;
+
 std::unique_ptr<UnlitMaterial> Material::MakeUnlit() {
   return std::make_unique<UnlitMaterial>();
 }
@@ -47,6 +49,8 @@ SceneContextOptions Material::GetContextOptions(const RenderPass& pass) const {
 /// UnlitMaterial
 ///
 
+UnlitMaterial::~UnlitMaterial() = default;
+
 void UnlitMaterial::SetColor(Color color) {
   color_ = color;
 }
@@ -94,6 +98,8 @@ void UnlitMaterial::BindToCommand(const SceneContext& scene_context,
 /// StandardMaterial
 ///
 
+StandardMaterial::~StandardMaterial() = default;
+
 void StandardMaterial::SetAlbedo(Color albedo) {
   albedo_ = albedo;
 }

impeller/scene/material.h

@@ -23,6 +23,8 @@ class StandardMaterial;
 
 class Material {
  public:
+  virtual ~Material();
+
   struct BlendConfig {
     BlendOperation color_op = BlendOperation::kAdd;
     BlendFactor source_color_factor = BlendFactor::kOne;
@@ -62,6 +64,8 @@ class Material {
 
 class UnlitMaterial final : public Material {
  public:
+  ~UnlitMaterial();
+
   void SetColor(Color color);
 
   void SetColorTexture(std::shared_ptr<Texture> color_texture);
@@ -86,6 +90,8 @@ class UnlitMaterial final : public Material {
 
 class StandardMaterial final : public Material {
  public:
+  ~StandardMaterial();
+
   void SetAlbedo(Color albedo);
   void SetRoughness(Scalar roughness);
   void SetMetallic(Scalar metallic);

impeller/scene/mesh.cc

@@ -17,23 +17,27 @@ Mesh::Mesh() = default;
 Mesh::~Mesh() = default;
 
 void Mesh::AddPrimitive(Primitive mesh) {
-  if (mesh.geometry_ == nullptr) {
+  if (mesh.geometry == nullptr) {
     VALIDATION_LOG << "Mesh geometry cannot be null.";
   }
-  if (mesh.material_ == nullptr) {
+  if (mesh.material == nullptr) {
     VALIDATION_LOG << "Mesh material cannot be null.";
   }
 
-  meshes_.push_back(std::move(mesh));
+  primitives_.push_back(std::move(mesh));
+}
+
+std::vector<Mesh::Primitive>& Mesh::GetPrimitives() {
+  return primitives_;
 }
 
 bool Mesh::Render(SceneEncoder& encoder, const Matrix& transform) const {
-  for (const auto& mesh : meshes_) {
+  for (const auto& mesh : primitives_) {
     SceneCommand command = {
         .label = "Mesh Primitive",
         .transform = transform,
-        .geometry = mesh.geometry_.get(),
-        .material = mesh.material_.get(),
+        .geometry = mesh.geometry.get(),
+        .material = mesh.material.get(),
     };
     encoder.Add(command);
   }

impeller/scene/mesh.h

@@ -18,19 +18,25 @@ namespace scene {
 class Mesh final {
  public:
   struct Primitive {
-    std::shared_ptr<Geometry> geometry_;
-    std::shared_ptr<Material> material_;
+    std::shared_ptr<Geometry> geometry;
+    std::shared_ptr<Material> material;
   };
 
   Mesh();
   ~Mesh();
 
+  Mesh(Mesh&& mesh);
+  Mesh& operator=(Mesh&& mesh);
+
   void AddPrimitive(Primitive mesh_);
+  std::vector<Primitive>& GetPrimitives();
 
   bool Render(SceneEncoder& encoder, const Matrix& transform) const;
 
  private:
-  std::vector<Primitive> meshes_;
+  std::vector<Primitive> primitives_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(Mesh);
 };
 
 }  // namespace scene

impeller/scene/node.cc

@@ -8,17 +8,70 @@
 
 #include "impeller/base/validation.h"
 #include "impeller/geometry/matrix.h"
+#include "impeller/scene/importer/scene_flatbuffers.h"
 #include "impeller/scene/mesh.h"
 #include "impeller/scene/node.h"
 #include "impeller/scene/scene_encoder.h"
 
 namespace impeller {
 namespace scene {
 
+std::optional<Node> Node::MakeFromFlatbuffer(fml::Mapping& mapping,
+                                             Allocator& allocator) {
+  flatbuffers::Verifier verifier(mapping.GetMapping(), mapping.GetSize());
+  if (!fb::VerifySceneBuffer(verifier)) {
+    return std::nullopt;
+  }
+
+  return Node::MakeFromFlatbuffer(*fb::GetScene(mapping.GetMapping()),
+                                  allocator);
+}
+
+Node Node::MakeFromFlatbuffer(const fb::Scene& scene, Allocator& allocator) {
+  Node result;
+
+  if (!scene.children()) {
+    return result;
+  }
+  for (const auto* child : *scene.children()) {
+    result.AddChild(Node::MakeFromFlatbuffer(*child, allocator));
+  }
+
+  return result;
+}
+
+Node Node::MakeFromFlatbuffer(const fb::Node& node, Allocator& allocator) {
+  Node result;
+
+  Mesh mesh;
+  for (const auto* primitives : *node.mesh_primitives()) {
+    auto geometry = Geometry::MakeFromFlatbuffer(*primitives, allocator);
+    mesh.AddPrimitive({geometry, Material::MakeUnlit()});
+  }
+  result.SetMesh(std::move(mesh));
+
+  if (!node.children()) {
+    return result;
+  }
+  for (const auto* child : *node.children()) {
+    result.AddChild(Node::MakeFromFlatbuffer(*child, allocator));
+  }
+
+  return result;
+}
+
 Node::Node() = default;
 
 Node::~Node() = default;
 
+Mesh::Mesh(Mesh&& mesh) = default;
+
+Mesh& Mesh::operator=(Mesh&& mesh) = default;
+
+Node::Node(Node&& node) = default;
+
+Node& Node::operator=(Node&& node) = default;
+
 void Node::SetLocalTransform(Matrix transform) {
   local_transform_ = transform;
 }
@@ -41,13 +94,33 @@ Matrix Node::GetGlobalTransform() const {
   return local_transform_;
 }
 
-void Node::AddChild(Node child) {
-  children_.push_back(child);
-  child.parent_ = this;
+bool Node::AddChild(Node node) {
+  if (node.parent_ != nullptr) {
+    VALIDATION_LOG
+        << "Cannot add a node as a child which already has a parent.";
+    return false;
+  }
+  node.parent_ = this;
+  children_.push_back(std::move(node));
+
+  Node& ref = children_.back();
+  for (Node& child : ref.children_) {
+    child.parent_ = &ref;
+  }
+
+  return true;
+}
+
+std::vector<Node>& Node::GetChildren() {
+  return children_;
+}
+
+void Node::SetMesh(Mesh mesh) {
+  mesh_ = std::move(mesh);
 }
 
-void Node::SetMesh(const Mesh& mesh) {
-  mesh_ = mesh;
+Mesh& Node::GetMesh() {
+  return mesh_;
 }
 
 bool Node::Render(SceneEncoder& encoder, const Matrix& parent_transform) const {

impeller/scene/node.h

@@ -20,18 +20,28 @@ namespace scene {
 
 class Node final {
  public:
+  static std::optional<Node> MakeFromFlatbuffer(fml::Mapping& mapping,
+                                                Allocator& allocator);
+  static Node MakeFromFlatbuffer(const fb::Scene& scene, Allocator& allocator);
+  static Node MakeFromFlatbuffer(const fb::Node& node, Allocator& allocator);
+
   Node();
   ~Node();
 
+  Node(Node&& node);
+  Node& operator=(Node&& node);
+
   void SetLocalTransform(Matrix transform);
   Matrix GetLocalTransform() const;
 
   void SetGlobalTransform(Matrix transform);
   Matrix GetGlobalTransform() const;
 
-  void AddChild(Node child);
+  bool AddChild(Node child);
+  std::vector<Node>& GetChildren();
 
-  void SetMesh(const Mesh& mesh);
+  void SetMesh(Mesh mesh);
+  Mesh& GetMesh();
 
   bool Render(SceneEncoder& encoder, const Matrix& parent_transform) const;
 
@@ -42,6 +52,8 @@ class Node final {
   Node* parent_ = nullptr;
   std::vector<Node> children_;
   Mesh mesh_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(Node);
 };
 
 }  // namespace scene

impeller/scene/scene_context.cc

@@ -49,7 +49,7 @@ SceneContext::SceneContext(std::shared_ptr<Context> context)
   {
     impeller::TextureDescriptor texture_descriptor;
     texture_descriptor.storage_mode = impeller::StorageMode::kHostVisible;
-    texture_descriptor.format = PixelFormat::kDefaultColor;
+    texture_descriptor.format = PixelFormat::kR8G8B8A8UNormInt;
     texture_descriptor.size = {1, 1};
     texture_descriptor.mip_count = 1u;
 

impeller/scene/scene_unittests.cc

@@ -47,7 +47,7 @@ TEST_P(SceneTest, CuboidUnlit) {
 
       Node& root = scene.GetRoot();
       root.SetLocalTransform(Matrix::MakeTranslation(-size / 2));
-      root.SetMesh(mesh);
+      root.SetMesh(std::move(mesh));
     }
 
     // Face towards the +Z direction (+X right, +Y up).
@@ -70,34 +70,26 @@ TEST_P(SceneTest, GLTFScene) {
 
   auto mapping =
       flutter::testing::OpenFixtureAsMapping("flutter_logo.glb.ipscene");
+  ASSERT_NE(mapping, nullptr);
 
-  flatbuffers::Verifier verifier(mapping->GetMapping(), mapping->GetSize());
-  ASSERT_TRUE(fb::VerifySceneBuffer(verifier));
-
-  // TODO(bdero): Add full scene deserialization utilities.
-  const auto* fb_scene = fb::GetScene(mapping->GetMapping());
-  const auto fb_nodes = fb_scene->children();
-  ASSERT_EQ(fb_nodes->size(), 1u);
-  const auto fb_meshes = fb_nodes->begin()->mesh_primitives();
-  ASSERT_EQ(fb_meshes->size(), 1u);
-  const auto* fb_mesh = fb_meshes->Get(0);
-  auto geometry = Geometry::MakeFromFBMeshPrimitive(*fb_mesh, *allocator);
-  ASSERT_NE(geometry, nullptr);
+  std::optional<Node> gltf_scene =
+      Node::MakeFromFlatbuffer(*mapping, *allocator);
+  ASSERT_TRUE(gltf_scene.has_value());
 
   std::shared_ptr<UnlitMaterial> material = Material::MakeUnlit();
-  auto bridge = CreateTextureForFixture("flutter_logo_baked.png");
-  material->SetColorTexture(bridge);
+  auto color_baked = CreateTextureForFixture("flutter_logo_baked.png");
+  material->SetColorTexture(color_baked);
   material->SetVertexColorWeight(0);
 
-  Renderer::RenderCallback callback = [&](RenderTarget& render_target) {
-    auto scene = Scene(GetContext());
+  ASSERT_EQ(gltf_scene->GetChildren().size(), 1u);
+  ASSERT_EQ(gltf_scene->GetChildren()[0].GetMesh().GetPrimitives().size(), 1u);
+  gltf_scene->GetChildren()[0].GetMesh().GetPrimitives()[0].material = material;
 
-    Mesh mesh;
-    mesh.AddPrimitive({geometry, material});
-
-    scene.GetRoot().SetLocalTransform(Matrix::MakeScale({3, 3, 3}));
-    scene.GetRoot().SetMesh(mesh);
+  auto scene = Scene(GetContext());
+  scene.GetRoot().AddChild(std::move(gltf_scene.value()));
+  scene.GetRoot().SetLocalTransform(Matrix::MakeScale({3, 3, 3}));
 
+  Renderer::RenderCallback callback = [&](RenderTarget& render_target) {
     Quaternion rotation({0, 1, 0}, -GetSecondsElapsed() * 0.5);
     Vector3 start_position(-1, -1.5, -5);