[Impeller Scene] Add offline mesh importer

ci/licenses_golden/licenses_flutter

@@ -1648,6 +1648,13 @@ FILE: ../../../flutter/impeller/scene/camera.cc
 FILE: ../../../flutter/impeller/scene/camera.h
 FILE: ../../../flutter/impeller/scene/geometry.cc
 FILE: ../../../flutter/impeller/scene/geometry.h
+FILE: ../../../flutter/impeller/scene/importer/importer.h
+FILE: ../../../flutter/impeller/scene/importer/importer_gltf.cc
+FILE: ../../../flutter/impeller/scene/importer/importer_main.cc
+FILE: ../../../flutter/impeller/scene/importer/mesh.fbs
+FILE: ../../../flutter/impeller/scene/importer/switches.cc
+FILE: ../../../flutter/impeller/scene/importer/switches.h
+FILE: ../../../flutter/impeller/scene/importer/types.h
 FILE: ../../../flutter/impeller/scene/material.cc
 FILE: ../../../flutter/impeller/scene/material.h
 FILE: ../../../flutter/impeller/scene/scene.cc

impeller/compiler/BUILD.gn

@@ -5,6 +5,24 @@
 import("//flutter/impeller/tools/impeller.gni")
 import("//flutter/shell/version/version.gni")
 
+impeller_component("utilities") {
+  # Current versions of libcxx have deprecated some of the UTF-16 string
+  # conversion APIs.
+  defines = [ "_LIBCPP_DISABLE_DEPRECATION_WARNINGS" ]
+
+  sources = [
+    "utilities.cc",
+    "utilities.h",
+  ]
+
+  public_deps = [
+    "../base",
+    "../geometry",
+    "../runtime_stage",
+    "//flutter/fml",
+  ]
+}
+
 impeller_component("compiler_lib") {
   include_dirs = [ "//third_party/vulkan-deps/spirv-cross/src/" ]
 
@@ -34,11 +52,10 @@ impeller_component("compiler_lib") {
     "switches.h",
     "types.cc",
     "types.h",
-    "utilities.cc",
-    "utilities.h",
   ]
 
   public_deps = [
+    ":utilities",
     "../base",
     "../geometry",
     "../runtime_stage",

impeller/fixtures/BUILD.gn

@@ -33,6 +33,11 @@ impeller_shaders("shader_fixtures") {
   }
 }
 
+scene_importer("geometry_fixtures") {
+  geometry = [ "flutter_logo.glb" ]
+  type = "gltf"
+}
+
 impellerc("runtime_stages") {
   shaders = [
     "ink_sparkle.frag",
@@ -87,6 +92,7 @@ group("fixtures") {
 
   public_deps = [
     ":file_fixtures",
+    ":geometry_fixtures",
     ":shader_fixtures",
   ]
 }

impeller/scene/importer/BUILD.gn

@@ -0,0 +1,93 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//flutter/impeller/tools/impeller.gni")
+import("//flutter/shell/version/version.gni")
+import("//third_party/flatbuffers/flatbuffers.gni")
+
+config("runtime_stage_config") {
+  configs = [ "//flutter/impeller:impeller_public_config" ]
+  include_dirs = [ "$root_gen_dir/flutter" ]
+}
+
+flatbuffers("importer_flatbuffers") {
+  flatbuffers = [ "mesh.fbs" ]
+  public_configs = [ ":runtime_stage_config" ]
+  public_deps = [ "//third_party/flatbuffers" ]
+}
+
+impeller_component("importer_lib") {
+  # Current versions of libcxx have deprecated some of the UTF-16 string
+  # conversion APIs.
+  defines = [ "_LIBCPP_DISABLE_DEPRECATION_WARNINGS" ]
+
+  sources = [
+    "importer.h",
+    "importer_gltf.cc",
+    "switches.cc",
+    "switches.h",
+    "types.h",
+  ]
+
+  public_deps = [
+    ":importer_flatbuffers",
+    "../../base",
+    "../../compiler:utilities",
+    "../../geometry",
+    "//flutter/fml",
+
+    # All third_party deps must be reflected below in the scene_importer_license
+    # target.
+    # TODO(bdero): Fix tinygltf compilation warnings.
+    #"//third_party/tinygltf",
+  ]
+}
+
+generated_file("scene_importer_license") {
+  source_path = rebase_path(".", "//flutter")
+  git_url = "https://github.com/flutter/engine/tree/$engine_version"
+  outputs = [ "$target_gen_dir/LICENSE.scene_importer.md" ]
+  contents = [
+    "# scene_importer",
+    "",
+    "This tool is used by the Flutter SDK to import 3D geometry.",
+    "",
+    "Source code for this tool: [flutter/engine/$source_path]($git_url/$source_path).",
+    "",
+    "## Licenses",
+    "",
+    "### scene_importer",
+    "",
+    read_file("//flutter/sky/packages/sky_engine/LICENSE", "string"),
+    "",
+
+    # These licenses are ignored by the main license checker, since they are not
+    # shipped to end-application binaries and only shipped as part of developer
+    # tooling in scene_importer. Add them here.
+    "## Additional open source licenses",
+    "",
+    "### tinygltf",
+    "",
+    read_file("//third_party/tinygltf/LICENSE", "string"),
+  ]
+}
+
+group("importer") {
+  deps = [
+    ":scene_importer",
+    ":scene_importer_license",
+  ]
+}
+
+impeller_component("scene_importer") {
+  target_type = "executable"
+
+  sources = [ "importer_main.cc" ]
+
+  deps = [ ":importer_lib" ]
+
+  metadata = {
+    entitlement_file_path = [ "scene_importer" ]
+  }
+}

impeller/scene/importer/importer.h

@@ -0,0 +1,19 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <array>
+#include <memory>
+
+#include "flutter/fml/mapping.h"
+#include "impeller/scene/importer/mesh_flatbuffers.h"
+
+namespace impeller {
+namespace scene {
+namespace importer {
+
+bool ParseGLTF(const fml::Mapping& source_mapping, fb::MeshT& out_mesh);
+
+}
+}  // namespace scene
+}  // namespace impeller

impeller/scene/importer/importer_gltf.cc

@@ -0,0 +1,24 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <array>
+#include <memory>
+
+#include "impeller/scene/importer/importer.h"
+
+#include "flutter/fml/mapping.h"
+
+namespace impeller {
+namespace scene {
+namespace importer {
+
+bool ParseGLTF(const fml::Mapping& source_mapping, fb::MeshT& out_mesh) {
+  // TODO(bdero): Parse source_mapping and populare out_mesh with just the first
+  //              mesh in the GLTF.
+  return true;
+}
+
+}  // namespace importer
+}  // namespace scene
+}  // namespace impeller

impeller/scene/importer/importer_main.cc

@@ -0,0 +1,108 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <filesystem>
+#include <memory>
+
+#include "flutter/fml/backtrace.h"
+#include "flutter/fml/command_line.h"
+#include "flutter/fml/file.h"
+#include "flutter/fml/macros.h"
+#include "flutter/fml/mapping.h"
+#include "impeller/base/strings.h"
+#include "impeller/compiler/utilities.h"
+#include "impeller/scene/importer/importer.h"
+#include "impeller/scene/importer/switches.h"
+#include "impeller/scene/importer/types.h"
+
+#include "third_party/flatbuffers/include/flatbuffers/flatbuffer_builder.h"
+
+namespace impeller {
+namespace scene {
+namespace importer {
+
+// Sets the file access mode of the file at path 'p' to 0644.
+static bool SetPermissiveAccess(const std::filesystem::path& p) {
+  auto permissions =
+      std::filesystem::perms::owner_read | std::filesystem::perms::owner_write |
+      std::filesystem::perms::group_read | std::filesystem::perms::others_read;
+  std::error_code error;
+  std::filesystem::permissions(p, permissions, error);
+  if (error) {
+    std::cerr << "Failed to set access on file '" << p
+              << "': " << error.message() << std::endl;
+    return false;
+  }
+  return true;
+}
+
+bool Main(const fml::CommandLine& command_line) {
+  fml::InstallCrashHandler();
+  if (command_line.HasOption("help")) {
+    Switches::PrintHelp(std::cout);
+    return true;
+  }
+
+  Switches switches(command_line);
+  if (!switches.AreValid(std::cerr)) {
+    std::cerr << "Invalid flags specified." << std::endl;
+    Switches::PrintHelp(std::cerr);
+    return false;
+  }
+
+  auto source_file_mapping =
+      fml::FileMapping::CreateReadOnly(switches.source_file_name);
+  if (!source_file_mapping) {
+    std::cerr << "Could not open input file." << std::endl;
+    return false;
+  }
+
+  fb::MeshT mesh;
+  bool success = false;
+  switch (switches.input_type) {
+    case SourceType::kGLTF:
+      success = ParseGLTF(*source_file_mapping, mesh);
+      break;
+    case SourceType::kUnknown:
+      std::cerr << "Unknown input type." << std::endl;
+      return false;
+  }
+  if (!success) {
+    std::cerr << "Failed to parse input file." << std::endl;
+    return false;
+  }
+
+  flatbuffers::FlatBufferBuilder builder;
+  builder.Finish(fb::Mesh::Pack(builder, &mesh));
+
+  auto output_file_name = std::filesystem::absolute(
+      std::filesystem::current_path() / switches.output_file_name);
+  fml::NonOwnedMapping mapping(builder.GetCurrentBufferPointer(),
+                               builder.GetSize());
+  if (!fml::WriteAtomically(*switches.working_directory,
+                            compiler::Utf8FromPath(output_file_name).c_str(),
+                            mapping)) {
+    std::cerr << "Could not write file to " << switches.output_file_name
+              << std::endl;
+    return false;
+  }
+
+  // Tools that consume the geometry data expect the access mode to be 0644.
+  if (!SetPermissiveAccess(output_file_name)) {
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace importer
+}  // namespace scene
+}  // namespace impeller
+
+int main(int argc, char const* argv[]) {
+  return impeller::scene::importer::Main(
+             fml::CommandLineFromPlatformOrArgcArgv(argc, argv))
+             ? EXIT_SUCCESS
+             : EXIT_FAILURE;
+}

impeller/scene/importer/mesh.fbs

@@ -0,0 +1,37 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+namespace impeller.fb;
+
+struct Vec2 {
+  x: float;
+  y: float;
+}
+
+struct Vec3 {
+  x: float;
+  y: float;
+  z: float;
+}
+
+struct Color {
+  r: float;
+  g: float;
+  b: float;
+}
+
+struct Vertex {
+  position: Vec3;
+  normal: Vec3;
+  tangent: Vec3;
+  texture_coords: Vec2;
+}
+
+table Mesh {
+  vertices: [Vertex];
+  indices: [uint16];
+}
+
+root_type Mesh;
+file_identifier "IPME";