Implementing glTF 1.0 parser

chrome/browser/android/vr_shell/gltf_parser.cc

+// Copyright 2017 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;
+
+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");

[cjgrant, 2017/03/21 16:16:47]

General comment for here and many other spots:  Feels like a "failed to parse"
result should be returned instead of blowing up on CHECK.  Deferring to Brandon
on this though.

[acondor_, 2017/03/22 16:25:28]

Done.

+
+  asset_ = base::MakeUnique<gltf::Asset>();
+
+  const base::DictionaryValue* sub_dict;
+  if (dict.GetDictionary("buffers", &sub_dict))
+    SetBuffers(*sub_dict);
+  if (dict.GetDictionary("bufferViews", &sub_dict))
+    SetBufferViews(*sub_dict);
+  if (dict.GetDictionary("accessors", &sub_dict))
+    SetAccessors(*sub_dict);
+  if (dict.GetDictionary("meshes", &sub_dict))
+    SetMeshes(*sub_dict);
+  if (dict.GetDictionary("nodes", &sub_dict))
+    SetNodes(*sub_dict);
+  if (dict.GetDictionary("scenes", &sub_dict))
+    SetScenes(*sub_dict);
+
+  std::string scene_key;
+  if (dict.GetString("scene", &scene_key)) {
+    auto scene_it = scene_ids_.find(scene_key);
+    CHECK(scene_it != scene_ids_.end());

[cjgrant, 2017/03/21 16:16:47]

Same question as above - anything that could fail due to bad input probably
shouldn't crash the app.

[acondor_, 2017/03/22 16:25:28]

Done.

+    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));
+    // TODO(acondor): Support files. Only inline data is supported now.
+    CHECK(uri.substr(0, kBase64HeaderSize) == kBase64Header);

[bajones, 2017/03/21 15:44:24]

This is a smart simplification for a first pass, but given that we're trying to
be sensitive to size forcing assets to be base64 encoded unfortunately works
against us. I don't think it should necessarily block this CL, but we may want
to consider supporting the binary glTF format up front if we're trying to avoid
multiple files. Then at least the buffers don't have to be encoded.

[acondor_, 2017/03/21 19:31:30]

For reference, our current model is < 20k and we are going to deliver it through
component updater.
But first I want to get the model rendered and then focus on issues about
delivering. At that point, I can implement the binary reader, which doesn't seem
like a great amount of work on top of this.

+
+    auto buffer = base::MakeUnique<gltf::Buffer>();
+    CHECK(base::Base64Decode(uri.substr(kBase64HeaderSize), buffer.get()));
+
+    int byte_length;
+    CHECK(buffer_dict->GetInteger("byteLength", &byte_length));
+    CHECK(int{buffer->length()} == byte_length);
+
+    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("byteOffset", &buffer_view->byte_offset));
+    buffer_view_dict->GetInteger("byteLength", &buffer_view->byte_length);
+    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));
+    accessor_dict->GetInteger("byteStride", &accessor->byte_stride);
+    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;
+    if (mesh_dict->GetList("primitives", &list)) {
+      for (const auto& primitive_value : *list) {
+        const base::DictionaryValue* primitive_dict;
+        CHECK(primitive_value->GetAsDictionary(&primitive_dict));
+
+        auto primitive = base::MakeUnique<gltf::Mesh::Primitive>();
+        std::string indices_key;
+        const base::DictionaryValue* attributes;
+        if (primitive_dict->GetString("indices", &indices_key)) {
+          auto accessor_it = accessor_ids_.find(indices_key);
+          CHECK(accessor_it != accessor_ids_.end());
+          primitive->indices = asset_->GetAccessor(accessor_it->second);
+        }
+        primitive_dict->GetInteger("mode", &primitive->mode);
+        if (primitive_dict->GetDictionary("attributes", &attributes)) {
+          for (base::DictionaryValue::Iterator it2(*attributes); !it2.IsAtEnd();
+               it2.Advance()) {
+            std::string accessor_key;
+            CHECK(it2.value().GetAsString(&accessor_key));
+            auto 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;
+    if (scene_dict->GetList("nodes", &list)) {
+      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