void CMesh2::CalcNormals()
	{
		normal_data_type_ = NormalDataType::VertexNormal;

		normal_directions_.clear();
		normal_indices_.clear();

		normal_directions_.resize(vertex_positions_.size());
		for (auto& triangle : draw_triangles_)
		{
			auto& a = triangle[0];
			auto& b = triangle[1];
			auto& c = triangle[2];
			auto normal = (vertex_positions_[b] - vertex_positions_[a]) ^ (vertex_positions_[c] - vertex_positions_[a]);
			normal_directions_[a] += normal;
			normal_directions_[b] += normal;
			normal_directions_[c] += normal;
		}

		for (auto& normal : normal_directions_)
		{
			if(normal != Cenit::Math::vector3_f::null())
			{
				normal.normalize();
			}
		}
	}