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loadGlTF.cpp
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loadGlTF.cpp
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// First define our filname, would probbably be better to prompt the user for one
const std::string& gltfFilename = "example.gltf"
// open the gltf file
std::ifstream jsonFile(gltfFilename, std::ios::binary);
// parse the json so we can use it later
Json::Value json;
try{
jsonFile >> json;
}catch(const std::exception& e){
std::cerr << "Json parsing error: " << e.what() << std::endl;
}
jsonFile.close();
// Extract the name of the bin file, for the sake of simplicity I'm assuming there's only one
std::string binFilename = json["buffers"][0]["uri"].asString();
// Open it with the cursor at the end of the file so we can determine it's size,
// We could techincally read the filesize from the gltf file, but I trust the file itself more
std::ifstream binFile = std::ifstream(binFilename, std::ios::binary | std::ios::ate);
// Read file length and then reset cursor
size_t binLength = binFile.tellg();
binFile.seekg(0);
std::vector<char> bin(binLength);
binFile.read(bin.data(), binLength);
binFile.close();
// Now that we have the files read out, let's actually do something with them
// This code prints out all the vertex positions for the first primitive
// Get the primitve we want to print out:
Json::Value& primitive = json["meshes"][0]["primitives"][0];
// Get the accessor for position:
Json::Value& positionAccessor = json["accessors"][primitive["attributes"]["POSITION"].asInt()];
// Get the bufferView
Json::Value& bufferView = json["bufferViews"][positionAccessor["bufferView"].asInt()];
// Now get the start of the float3 array by adding the bufferView byte offset to the bin pointer
// It's a little sketchy to cast to a raw float array, but hey, it works.
float* buffer = (float*)(bin.data() + bufferView["byteOffset"].asInt());
// Print out all the vertex positions
for (int i = 0; i < positionAccessor["count"].asInt(); ++i)
{
std::cout << "(" << buffer[i*3] << ", " << buffer[i*3 + 1] << ", " << buffer[i*3 + 2] << ")" << std::endl;
}
// And as a cherry on top, let's print out the total number of verticies
std::cout << "vertices: " << positionAccessor["count"].asInt() << std::endl;