Add embedded GLB buffer & customization

spnda · Jan 2, 2024 · ee3a673 · ee3a673
1 parent a902b3a
commit ee3a673
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Showing 2 changed files with 37 additions and 3 deletions.
diff --git a/include/fastgltf/core.hpp b/include/fastgltf/core.hpp
@@ -805,6 +805,8 @@ namespace fastgltf {
     protected:
         Error errorCode = Error::None;
 
+        Optional<std::size_t> binaryBufferIndex = 0;
+
         std::filesystem::path bufferFolder = "";
         std::filesystem::path imageFolder = "";
 
@@ -844,6 +846,11 @@ namespace fastgltf {
          */
         void setImagePath(std::filesystem::path folder);
 
+        /**
+         * Sets the index of the buffer that should be embedded into the GLB file.
+         */
+        void setBinaryBufferIndex(std::size_t idx);
+
         /**
          * Converts the Asset into a glTF JSON string.
          */

diff --git a/src/fastgltf.cpp b/src/fastgltf.cpp
@@ -3574,6 +3574,10 @@ void fg::Exporter::setImagePath(std::filesystem::path folder) {
     imageFolder = std::move(folder);
 }
 
+void fg::Exporter::setBinaryBufferIndex(std::size_t idx) {
+    binaryBufferIndex = idx;
+}
+
 void fg::Exporter::writeAccessors(const Asset& asset, std::string& json) {
 	if (asset.accessors.empty())
 		return;
@@ -3639,13 +3643,17 @@ void fg::Exporter::writeBuffers(const Asset& asset, std::string& json) {
 	for (auto it = asset.buffers.begin(); it != asset.buffers.end(); ++it) {
 		json += '{';
 
-        auto bufferIdx = std::distance(asset.buffers.begin(), it);
+        auto bufferIdx = static_cast<std::size_t>(std::distance(asset.buffers.begin(), it));
 		std::visit(visitor {
 			[&](auto arg) {
 				// Covers BufferView and CustomBuffer.
 				errorCode = Error::InvalidGltf;
 			},
 			[&](const sources::Vector& vector) {
+                if (binaryBufferIndex.has_value() && binaryBufferIndex.value() == bufferIdx) {
+                    bufferPaths.emplace_back(std::nullopt);
+                    return;
+                }
                 auto path = getBufferFilePath(asset, bufferIdx);
                 json += std::string(R"("uri":")") + path.string() + '"' + ',';
                 bufferPaths.emplace_back(path);
@@ -4370,6 +4378,11 @@ fg::Expected<fg::ExportResult<std::vector<std::byte>>> fg::Exporter::writeGltfBi
 
     ExportResult<std::vector<std::byte>> result;
 
+    if (!binaryBufferIndex.has_value()) {
+        binaryBufferIndex = 0;
+    }
+    const std::size_t bufferIndex = binaryBufferIndex.value();
+
     // Generate the JSON.
     auto expected = writeGltfJson(asset, options);
     if (expected.error() != Error::None) {
@@ -4379,8 +4392,10 @@ fg::Expected<fg::ExportResult<std::vector<std::byte>>> fg::Exporter::writeGltfBi
     result.bufferPaths = std::move(json.bufferPaths);
     result.imagePaths = std::move(json.imagePaths);
 
-    const bool withEmbeddedBuffer = false;
-    //const bool withEmbeddedBuffer = !asset.buffers.empty() || asset.buffers.front().byteLength < std::numeric_limits<std::uint32_t>::max();
+    const bool withEmbeddedBuffer = bufferIndex < asset.buffers.size()
+            && std::get_if<sources::Vector>(&asset.buffers[bufferIndex].data) != nullptr // We only support writing Vectors as embedded buffers
+            && asset.buffers[bufferIndex].byteLength < std::numeric_limits<decltype(BinaryGltfChunk::chunkLength)>::max();
+
     std::size_t binarySize = sizeof(BinaryGltfHeader) + sizeof(BinaryGltfChunk) + json.output.size();
     if (withEmbeddedBuffer) {
         binarySize += sizeof(BinaryGltfChunk) + asset.buffers.front().byteLength;
@@ -4405,6 +4420,18 @@ fg::Expected<fg::ExportResult<std::vector<std::byte>>> fg::Exporter::writeGltfBi
 
     write(json.output.data(), json.output.size() * sizeof(decltype(json.output)::value_type));
 
+    if (withEmbeddedBuffer) {
+        const auto& buffer = asset.buffers[bufferIndex];
+
+        BinaryGltfChunk dataChunk;
+        dataChunk.chunkType = binaryGltfDataChunkMagic;
+        dataChunk.chunkLength = buffer.byteLength;
+        write(&dataChunk, sizeof dataChunk);
+
+        const auto* vector = std::get_if<sources::Vector>(&buffer.data);
+        write(vector->bytes.data(), buffer.byteLength);
+    }
+
     return Expected { std::move(result) };
 }