PLY to FRawMesh

zoox::unique_ptr<FRawMesh> ReadPly(ByteBuffer const & buffer)
{
	// read the header
	constexpr auto header =
		"ply\n\n"
		"format binary_little_endian 1.0\n"
		"comment This contains a Splatted Point Cloud\n"
		"element vertex %d\n"
		"property float x\n"
		"property float y\n"
		"property float z\n"
		"property float nx\n"
		"property float ny\n"
		"property float nz\n"
		"property uchar red\n"
		"property uchar green\n"
		"property uchar blue\n"
		"property uchar alpha\n"
		"element face %d\n"
		"property list uchar int vertex_indices\n"
		"end_header\n%n";

	int num_vertices, num_faces, header_bytes;
	int scanned = zoox::sscanf(reinterpret_cast<char const *>(buffer.data()), header, &num_vertices, &num_faces, &header_bytes);
	if (scanned != 2)
	{
		return nullptr;
	}

	// map out the lists of vertices and faces
#pragma pack(push, 1)
	struct Vertex
	{
		zoox::array<float, 3> position;
		zoox::array<float, 3> normal;
		zoox::array<zoox::uint8_t, 4> color;
	};

	struct Face
	{
		zoox::uint8_t num_faces;
		zoox::array<zoox::int32_t, 3> indices;
	};
#pragma pack(pop)

	auto vertices_begin = reinterpret_cast<Vertex const *>(buffer.data() + header_bytes);
	auto vertices_end = vertices_begin + num_vertices;

	auto faces_begin = reinterpret_cast<Face const *>(vertices_end);
	auto faces_end = faces_begin + num_faces;

	// ensure that the file matches the lists
	if (reinterpret_cast<ByteBuffer::value_type const *>(faces_end) != buffer.data() + buffer.size())
	{
		return nullptr;
	}

	// allocate a return object
	auto result = zoox::unique_ptr<FRawMesh>(new FRawMesh);

	// read the vertex positions
	result->VertexPositions.Reserve(num_vertices);
	for (auto vertex_iterator = vertices_begin; vertex_iterator != vertices_end; ++vertex_iterator)
	{
		result->VertexPositions.Emplace(
			vertex_iterator->position[0],
			vertex_iterator->position[1],
			vertex_iterator->position[2]);
	}

	auto num_wedges = num_faces * 3;
	result->WedgeColors.Reserve(num_wedges);
	result->WedgeIndices.Reserve(num_wedges);
	result->WedgeTangentX.Reserve(num_wedges);
	result->WedgeTangentY.Reserve(num_wedges);
	result->WedgeTangentZ.Reserve(num_wedges);
	//result->WedgeTexCoords.Reserve(num_wedges);
	for (auto face_iterator = faces_begin; face_iterator != faces_end; ++face_iterator)
	{
		if (face_iterator->num_faces != 3)
		{
			return nullptr;
		}

		for (auto index : face_iterator->indices)
		{
			if (index < 0 || index >= num_vertices)
			{
				return nullptr;
			}

			auto const & vertex = vertices_begin[index];
			result->WedgeColors.Emplace(
				vertex.color[0],
				vertex.color[1],
				vertex.color[2],
				vertex.color[3]);
			result->WedgeIndices.Emplace(index);
			result->WedgeTangentX.Emplace(FVector::ZeroVector);
			result->WedgeTangentY.Emplace(FVector::ZeroVector);
			result->WedgeTangentZ.Emplace(
				vertex.normal[0],
				vertex.normal[1],
				vertex.normal[2]);
			//result->WedgeTexCoords.Emplace(FVector2D::ZeroVector);
		}
	}

	ensure(result->WedgeColors.Num() == num_wedges);
	ensure(result->WedgeIndices.Num() == num_wedges);
	ensure(result->WedgeTangentX.Num() == num_wedges);
	ensure(result->WedgeTangentY.Num() == num_wedges);
	ensure(result->WedgeTangentZ.Num() == num_wedges);

	return result;
}