Function copyShCoeff

CesiumGltfReader/src/decodeSpz.cpp:112–167

}

void copyShCoeff(
    GltfReaderResult& readGltf,
    CesiumGltf::MeshPrimitive& primitive,
    CesiumGltf::Buffer& buffer,
    const spz::GaussianCloud& gaussian,
    int degree,
    int coeffIndex) {
  size_t base = 0;
  size_t stride = 0;
  if (degree == 1) {
    stride = 9;
  } else if (degree == 2) {
    stride = 24;
    base = 9;
  } else if (degree == 3) {
    stride = 45;
    base = 24;
  }

  CesiumGltf::Accessor* pAccessor = findAccessor(
      readGltf,
      primitive,
      fmt::format(
          "KHR_gaussian_splatting:SH_DEGREE_{}_COEF_{}",
          degree,
          coeffIndex));
  if (!pAccessor) {
    return;
  }

  CESIUM_ASSERT(readGltf.model);

  // Some gaussian splats seem to set this value as VEC4, even though the spec
  // requires VEC3.
  pAccessor->type = CesiumGltf::Accessor::Type::VEC3;

  pAccessor->bufferView =
      static_cast<int32_t>(readGltf.model->bufferViews.size());
  CesiumGltf::BufferView& bufferView =
      readGltf.model->bufferViews.emplace_back();
  bufferView.buffer = static_cast<int32_t>(readGltf.model->buffers.size() - 1);
  bufferView.byteLength = static_cast<int64_t>(
      sizeof(float) * static_cast<size_t>(gaussian.numPoints) * 3);

  size_t start = buffer.cesium.data.size();
  bufferView.byteOffset = static_cast<int64_t>(start);
  buffer.cesium.data.resize(start + static_cast<size_t>(bufferView.byteLength));
  for (size_t i = 0; i < static_cast<size_t>(gaussian.numPoints); i++) {
    const size_t idx = i * stride + base + static_cast<size_t>(coeffIndex) * 3;
    std::memcpy(
        buffer.cesium.data.data() + start,
        gaussian.sh.data() + idx,
        sizeof(float) * 3);
    start += sizeof(float) * 3;
  }
}

void decodePrimitive(