Skip to content

Commit b400371

Browse files
marty-johnson59marty-johnson59
authored
Merge pull request #338 from KhronosGroup/fix_276
Make tutorial code snippet match source code
2 parents 0a81443 + ab89e23 commit b400371

1 file changed

Lines changed: 89 additions & 60 deletions

File tree

‎en/15_GLTF_KTX2_Migration.adoc‎

Lines changed: 89 additions & 60 deletions
Original file line numberDiff line numberDiff line change
@@ -141,102 +141,131 @@ Now, let's modify our `loadModel()` function to use tinygltf instead of tinyobjl
141141

142142
[,c{pp}]
143143
----
144-
void loadModel() {
144+
void loadModel()
145+
{
145146
// Use tinygltf to load the model instead of tinyobjloader
146-
tinygltf::Model model;
147+
tinygltf::Model model;
147148
tinygltf::TinyGLTF loader;
148-
std::string err;
149-
std::string warn;
149+
std::string err;
150+
std::string warn;
150151
151-
bool ret = loader.LoadASCIIFromFile(&model, &err, &warn, MODEL_PATH);
152+
bool ret = loader.LoadBinaryFromFile(&model, &err, &warn, MODEL_PATH);
152153
153-
if (!warn.empty()) {
154+
if (!warn.empty())
155+
{
154156
std::cout << "glTF warning: " << warn << std::endl;
155157
}
156158
157-
if (!err.empty()) {
159+
if (!err.empty())
160+
{
158161
std::cout << "glTF error: " << err << std::endl;
159162
}
160163
161-
if (!ret) {
164+
if (!ret)
165+
{
162166
throw std::runtime_error("Failed to load glTF model");
163167
}
164168
165-
// Process all meshes in the model
166-
std::unordered_map<Vertex, uint32_t> uniqueVertices{};
169+
vertices.clear();
170+
indices.clear();
167171
168-
for (const auto& mesh : model.meshes) {
169-
for (const auto& primitive : mesh.primitives) {
172+
// Process all meshes in the model
173+
for (const auto &mesh : model.meshes)
174+
{
175+
for (const auto &primitive : mesh.primitives)
176+
{
170177
// Get indices
171-
const tinygltf::Accessor& indexAccessor = model.accessors[primitive.indices];
172-
const tinygltf::BufferView& indexBufferView = model.bufferViews[indexAccessor.bufferView];
173-
const tinygltf::Buffer& indexBuffer = model.buffers[indexBufferView.buffer];
178+
const tinygltf::Accessor &indexAccessor = model.accessors[primitive.indices];
179+
const tinygltf::BufferView &indexBufferView = model.bufferViews[indexAccessor.bufferView];
180+
const tinygltf::Buffer &indexBuffer = model.buffers[indexBufferView.buffer];
174181
175182
// Get vertex positions
176-
const tinygltf::Accessor& posAccessor = model.accessors[primitive.attributes.at("POSITION")];
177-
const tinygltf::BufferView& posBufferView = model.bufferViews[posAccessor.bufferView];
178-
const tinygltf::Buffer& posBuffer = model.buffers[posBufferView.buffer];
183+
const tinygltf::Accessor &posAccessor = model.accessors[primitive.attributes.at("POSITION")];
184+
const tinygltf::BufferView &posBufferView = model.bufferViews[posAccessor.bufferView];
185+
const tinygltf::Buffer &posBuffer = model.buffers[posBufferView.buffer];
179186
180187
// Get texture coordinates if available
181-
bool hasTexCoords = primitive.attributes.find("TEXCOORD_0") != primitive.attributes.end();
182-
const tinygltf::Accessor* texCoordAccessor = nullptr;
183-
const tinygltf::BufferView* texCoordBufferView = nullptr;
184-
const tinygltf::Buffer* texCoordBuffer = nullptr;
185-
186-
if (hasTexCoords) {
187-
texCoordAccessor = &model.accessors[primitive.attributes.at("TEXCOORD_0")];
188+
bool hasTexCoords = primitive.attributes.find("TEXCOORD_0") != primitive.attributes.end();
189+
const tinygltf::Accessor *texCoordAccessor = nullptr;
190+
const tinygltf::BufferView *texCoordBufferView = nullptr;
191+
const tinygltf::Buffer *texCoordBuffer = nullptr;
192+
193+
if (hasTexCoords)
194+
{
195+
texCoordAccessor = &model.accessors[primitive.attributes.at("TEXCOORD_0")];
188196
texCoordBufferView = &model.bufferViews[texCoordAccessor->bufferView];
189-
texCoordBuffer = &model.buffers[texCoordBufferView->buffer];
197+
texCoordBuffer = &model.buffers[texCoordBufferView->buffer];
190198
}
191199
192-
// Process vertices
193-
for (size_t i = 0; i < posAccessor.count; i++) {
200+
uint32_t baseVertex = static_cast<uint32_t>(vertices.size());
201+
202+
for (size_t i = 0; i < posAccessor.count; i++)
203+
{
194204
Vertex vertex{};
195205
196-
// Get position
197-
const float* pos = reinterpret_cast<const float*>(&posBuffer.data[posBufferView.byteOffset + posAccessor.byteOffset + i * 12]);
198-
vertex.pos = {pos[0], pos[1], pos[2]};
206+
const float *pos = reinterpret_cast<const float *>(&posBuffer.data[posBufferView.byteOffset + posAccessor.byteOffset + i * 12]);
207+
// glTF uses a right-handed coordinate system with Y-up
208+
// Vulkan uses a right-handed coordinate system with Y-down
209+
// We need to flip the Y coordinate
210+
vertex.pos = {pos[0], -pos[1], pos[2]};
199211
200-
// Get texture coordinates if available
201-
if (hasTexCoords) {
202-
const float* texCoord = reinterpret_cast<const float*>(&texCoordBuffer->data[texCoordBufferView->byteOffset + texCoordAccessor->byteOffset + i * 8]);
203-
vertex.texCoord = {texCoord[0], 1.0f - texCoord[1]};
204-
} else {
212+
if (hasTexCoords)
213+
{
214+
const float *texCoord = reinterpret_cast<const float *>(&texCoordBuffer->data[texCoordBufferView->byteOffset + texCoordAccessor->byteOffset + i * 8]);
215+
vertex.texCoord = {texCoord[0], texCoord[1]};
216+
}
217+
else
218+
{
205219
vertex.texCoord = {0.0f, 0.0f};
206220
}
207221
208-
// Set default color
209222
vertex.color = {1.0f, 1.0f, 1.0f};
210223
211-
// Add vertex if unique
212-
if (!uniqueVertices.contains(vertex)) {
213-
uniqueVertices[vertex] = static_cast<uint32_t>(vertices.size());
214-
vertices.push_back(vertex);
215-
}
224+
vertices.push_back(vertex);
225+
}
226+
227+
const unsigned char *indexData = &indexBuffer.data[indexBufferView.byteOffset + indexAccessor.byteOffset];
228+
size_t indexCount = indexAccessor.count;
229+
size_t indexStride = 0;
230+
231+
// Determine index stride based on component type
232+
if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT)
233+
{
234+
indexStride = sizeof(uint16_t);
235+
}
236+
else if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT)
237+
{
238+
indexStride = sizeof(uint32_t);
239+
}
240+
else if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE)
241+
{
242+
indexStride = sizeof(uint8_t);
216243
}
244+
else
245+
{
246+
throw std::runtime_error("Unsupported index component type");
247+
}
248+
249+
indices.reserve(indices.size() + indexCount);
217250
218-
// Process indices
219-
const unsigned char* indexData = &indexBuffer.data[indexBufferView.byteOffset + indexAccessor.byteOffset];
251+
for (size_t i = 0; i < indexCount; i++)
252+
{
253+
uint32_t index = 0;
220254
221-
// Handle different index component types
222-
if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT) {
223-
const uint16_t* indices16 = reinterpret_cast<const uint16_t*>(indexData);
224-
for (size_t i = 0; i < indexAccessor.count; i++) {
225-
Vertex vertex = vertices[indices16[i]];
226-
indices.push_back(uniqueVertices[vertex]);
255+
if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT)
256+
{
257+
index = *reinterpret_cast<const uint16_t *>(indexData + i * indexStride);
227258
}
228-
} else if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT) {
229-
const uint32_t* indices32 = reinterpret_cast<const uint32_t*>(indexData);
230-
for (size_t i = 0; i < indexAccessor.count; i++) {
231-
Vertex vertex = vertices[indices32[i]];
232-
indices.push_back(uniqueVertices[vertex]);
259+
else if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT)
260+
{
261+
index = *reinterpret_cast<const uint32_t *>(indexData + i * indexStride);
233262
}
234-
} else if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE) {
235-
const uint8_t* indices8 = reinterpret_cast<const uint8_t*>(indexData);
236-
for (size_t i = 0; i < indexAccessor.count; i++) {
237-
Vertex vertex = vertices[indices8[i]];
238-
indices.push_back(uniqueVertices[vertex]);
263+
else if (indexAccessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE)
264+
{
265+
index = *reinterpret_cast<const uint8_t *>(indexData + i * indexStride);
239266
}
267+
268+
indices.push_back(baseVertex + index);
240269
}
241270
}
242271
}

0 commit comments

Comments
 (0)