Implementing glTF 1.0 parser

chrome/browser/android/vr_shell/gltf_parser.cc

+// Copyright 2016 The Chromium 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 "chrome/browser/android/vr_shell/gltf_parser.h"
+
+#include "base/base64.h"
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+
+namespace vr_shell {
+
+constexpr char kBase64Header[] = "data:application/octet-stream;base64,";
+constexpr size_t kBase64HeaderSize = 37;
+
+namespace gltf {
+
+const std::unordered_map<std::string, Type> kTypeMap = {
+    {"SCALAR", SCALAR}, {"VEC2", VEC2}, {"VEC3", VEC3}, {"VEC4", VEC4},
+    {"MAT2", MAT2},     {"MAT3", MAT3}, {"MAT4", MAT4},
+};
+
+Type GetType(const std::string& type) {
+  auto it = kTypeMap.find(type);
+  CHECK(it != kTypeMap.end());
+  return it->second;
+}
+
+Primitive::Primitive() : indices(nullptr), mode(0) {}
+
+Primitive::~Primitive() = default;
+
+Mesh::Mesh() {}
+
+Mesh::~Mesh() = default;
+
+Node::Node() {}
+
+Node::~Node() = default;
+
+Scene::Scene() {}
+
+Scene::~Scene() = default;
+
+Asset::Asset() : scene_(nullptr) {}
+
+Asset::~Asset() = default;
+
+}  // namespace gltf
+
+GltfParser::GltfParser() {}
+
+GltfParser::~GltfParser() = default;
+
+std::unique_ptr<gltf::Asset> GltfParser::Parse(
+    const base::DictionaryValue& dict) {
+  std::string gltf_version;
+  CHECK(dict.GetString("asset.version", &gltf_version));
+  CHECK(gltf_version == "1.0");
+
+  asset_ = base::MakeUnique<gltf::Asset>();
+
+  const base::DictionaryValue* sub_dict;
+  CHECK(dict.GetDictionary("buffers", &sub_dict));
+  SetBuffers(*sub_dict);
+  CHECK(dict.GetDictionary("bufferViews", &sub_dict));
+  SetBufferViews(*sub_dict);
+  CHECK(dict.GetDictionary("accessors", &sub_dict));
+  SetAccessors(*sub_dict);
+  CHECK(dict.GetDictionary("meshes", &sub_dict));
+  SetMeshes(*sub_dict);
+  CHECK(dict.GetDictionary("nodes", &sub_dict));
+  SetNodes(*sub_dict);
+  CHECK(dict.GetDictionary("scenes", &sub_dict));
+  SetScenes(*sub_dict);
+  std::string scene_key;
+  CHECK(dict.GetString("scene", &scene_key));
+  auto scene_it = scene_ids_.find(scene_key);
+  CHECK(scene_it != scene_ids_.end());
+  asset_->SetScene(asset_->GetScene(scene_it->second));
+
+  return std::move(asset_);
+}
+
+void GltfParser::SetBuffers(const base::DictionaryValue& dict) {
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* buffer_dict;
+    CHECK(it.value().GetAsDictionary(&buffer_dict));
+
+    std::string uri;
+    CHECK(buffer_dict->GetString("uri", &uri));
+    // Only inline data is supported

[mthiesse, 2017/03/21 16:06:54]

nit: add period.

+    CHECK(uri.substr(0, kBase64HeaderSize) == kBase64Header);
+
+    auto buffer = base::MakeUnique<gltf::Buffer>();
+    CHECK(base::Base64Decode(uri.substr(kBase64HeaderSize), buffer.get()));
+
+    int byte_length;
+    CHECK(buffer_dict->GetInteger("byteLength", &byte_length));

[mthiesse, 2017/03/21 16:06:54]

byteLength isn't required by the spec, add a comment that because we only
support inline data we need a length?

[acondor_, 2017/03/21 19:31:29]

Actually we don't need it.

+    CHECK(int{buffer->length()} == byte_length);

[mthiesse, 2017/03/21 16:06:54]

static_cast<int>(buffer->length())

[acondor_, 2017/03/21 19:31:29]

Done.

+
+    buffer_ids_[it.key()] = asset_->AddBuffer(std::move(buffer));
+  }
+}
+
+void GltfParser::SetBufferViews(const base::DictionaryValue& dict) {
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* buffer_view_dict;
+    CHECK(it.value().GetAsDictionary(&buffer_view_dict));
+
+    auto buffer_view = base::MakeUnique<gltf::BufferView>();
+    std::string buffer_key;
+    CHECK(buffer_view_dict->GetString("buffer", &buffer_key));
+    auto buffer_it = buffer_ids_.find(buffer_key);
+    CHECK(buffer_it != buffer_ids_.end());
+    buffer_view->buffer = asset_->GetBuffer(buffer_it->second);
+    CHECK(
+        buffer_view_dict->GetInteger("byteLength", &buffer_view->byte_length));

[mthiesse, 2017/03/21 16:06:54]

byteLength and target are not required per the spec, comment on why we need them
to be there?

[acondor_, 2017/03/21 19:31:29]

Acknowledged.

+    CHECK(
+        buffer_view_dict->GetInteger("byteOffset", &buffer_view->byte_offset));
+    CHECK(buffer_view_dict->GetInteger("target", &buffer_view->target));
+
+    buffer_view_ids_[it.key()] = asset_->AddBufferView(std::move(buffer_view));
+  }
+}
+
+void GltfParser::SetAccessors(const base::DictionaryValue& dict) {
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* accessor_dict;
+    CHECK(it.value().GetAsDictionary(&accessor_dict));
+
+    auto accessor = base::MakeUnique<gltf::Accessor>();
+    std::string buffer_view_key;
+    std::string type_str;
+    CHECK(accessor_dict->GetString("bufferView", &buffer_view_key));
+    auto buffer_view_it = buffer_view_ids_.find(buffer_view_key);
+    CHECK(buffer_view_it != buffer_view_ids_.end());
+    accessor->buffer_view = asset_->GetBufferView(buffer_view_it->second);
+    CHECK(accessor_dict->GetInteger("byteOffset", &accessor->byte_offset));
+    CHECK(accessor_dict->GetInteger("byteStride", &accessor->byte_stride));

[mthiesse, 2017/03/21 16:06:54]

Also not required per spec, add comment?

[acondor_, 2017/03/21 19:31:29]

Acknowledged.

+    CHECK(
+        accessor_dict->GetInteger("componentType", &accessor->component_type));
+    CHECK(accessor_dict->GetInteger("count", &accessor->count));
+    CHECK(accessor_dict->GetString("type", &type_str));
+    accessor->type = gltf::GetType(type_str);
+
+    accessor_ids_[it.key()] = asset_->AddAccessor(std::move(accessor));
+  }
+}
+
+void GltfParser::SetMeshes(const base::DictionaryValue& dict) {
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* mesh_dict;
+    CHECK(it.value().GetAsDictionary(&mesh_dict));
+
+    auto mesh = base::MakeUnique<gltf::Mesh>();
+    const base::ListValue* list;
+    CHECK(mesh_dict->GetList("primitives", &list));
+    for (const auto& primitive_value : *list) {

[mthiesse, 2017/03/21 16:06:54]

nit: Move parsing of mesh.primitive into separate function for readability.

+      const base::DictionaryValue* primitive_dict;

[mthiesse, 2017/03/21 16:06:54]

Add comment that we ignore the required material attribute as we don't support
meshes.

[acondor_, 2017/03/21 19:31:29]

Done.

+      CHECK(primitive_value->GetAsDictionary(&primitive_dict));
+
+      auto primitive = base::MakeUnique<gltf::Primitive>();
+      std::string indices_key;
+      const base::DictionaryValue* attributes;
+      CHECK(primitive_dict->GetString("indices", &indices_key));

[mthiesse, 2017/03/21 16:06:54]

Add comment, not required per spec.

[acondor_, 2017/03/21 19:31:29]

Acknowledged.

+      auto accessor_it = accessor_ids_.find(indices_key);
+      CHECK(accessor_it != accessor_ids_.end());
+      primitive->indices = asset_->GetAccessor(accessor_it->second);
+      CHECK(primitive_dict->GetInteger("mode", &primitive->mode));

[mthiesse, 2017/03/21 16:06:54]

Add comment, not required per spec.

[acondor_, 2017/03/21 19:31:29]

Acknowledged.

+      CHECK(primitive_dict->GetDictionary("attributes", &attributes));

[mthiesse, 2017/03/21 16:06:54]

Attributes isn't required per spec. Do we need it, or can we handle empty
attributes?

[acondor_, 2017/03/21 19:31:29]

We can handle them. Recall that the only model we will use at first is
controlled by us.

+      for (base::DictionaryValue::Iterator it2(*attributes); !it2.IsAtEnd();
+           it2.Advance()) {
+        std::string accessor_key;
+        CHECK(it2.value().GetAsString(&accessor_key));
+        accessor_it = accessor_ids_.find(accessor_key);
+        CHECK(accessor_it != accessor_ids_.end());
+        primitive->attributes[it2.key()] =
+            asset_->GetAccessor(accessor_it->second);
+      }
+
+      mesh->primitives.push_back(std::move(primitive));
+    }
+
+    mesh_ids_[it.key()] = asset_->AddMesh(std::move(mesh));
+  }
+}
+
+void GltfParser::SetNodes(const base::DictionaryValue& dict) {
+  std::unordered_map<std::string, gltf::Node*> nodes;
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* node_dict;
+    CHECK(it.value().GetAsDictionary(&node_dict));
+
+    auto node = base::MakeUnique<gltf::Node>();
+    const base::ListValue* list;
+    if (node_dict->GetList("meshes", &list)) {
+      std::string mesh_key;
+      for (const auto& mesh_value : *list) {
+        CHECK(mesh_value->GetAsString(&mesh_key));
+        auto mesh_it = mesh_ids_.find(mesh_key);
+        CHECK(mesh_it != mesh_ids_.end());
+        node->meshes.push_back(asset_->GetMesh(mesh_it->second));
+      }
+    }
+
+    nodes[it.key()] = node.get();
+    node_ids_[it.key()] = asset_->AddNode(std::move(node));
+  }
+
+  // Processing children after all nodes have been added to the asset.
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* node_dict;
+    it.value().GetAsDictionary(&node_dict);
+
+    gltf::Node* node = nodes[it.key()];
+    const base::ListValue* list;
+    if (node_dict->GetList("children", &list)) {
+      std::string node_key;
+      for (const auto& mesh_value : *list) {
+        CHECK(mesh_value->GetAsString(&node_key));
+        auto node_it = nodes.find(node_key);
+        CHECK(node_it != nodes.end());
+        node->children.push_back(node_it->second);
+      }
+    }
+  }
+}
+
+void GltfParser::SetScenes(const base::DictionaryValue& dict) {
+  for (base::DictionaryValue::Iterator it(dict); !it.IsAtEnd(); it.Advance()) {
+    const base::DictionaryValue* scene_dict;
+    CHECK(it.value().GetAsDictionary(&scene_dict));
+
+    auto scene = base::MakeUnique<gltf::Scene>();
+    const base::ListValue* list;
+    CHECK(scene_dict->GetList("nodes", &list));

[mthiesse, 2017/03/21 16:06:54]

Not required per spec

[acondor_, 2017/03/21 19:31:29]

Acknowledged.

+    std::string node_key;
+    for (const auto& node_value : *list) {
+      CHECK(node_value->GetAsString(&node_key));
+      auto node_it = node_ids_.find(node_key);
+      CHECK(node_it != node_ids_.end());
+      scene->nodes.push_back(asset_->GetNode(node_it->second));
+    }
+
+    scene_ids_[it.key()] = asset_->AddScene(std::move(scene));
+  }
+}
+
+}  // namespace vr_shell