for(unsigned int z = 1; z < N; z++)
	{
		for(unsigned int x = 1; x < M; x++)
		{
			index = z * M + x;
			indices[indices_index++] = index;
			indices[indices_index++] = index - 1;
			indices[indices_index++] = index - M - 1;

			vec3 a = vertices[index].pos;
			vec3 b = vertices[index - 1].pos;
			vec3 c = vertices[index - M - 1].pos;
			vec3 ab = b - a;
			vec3 ac = c - a;
			vec3 n = cross(ab, ac);

			vertices_ex[index        ].normals.push_back(n);
			vertices_ex[index - 1    ].normals.push_back(n);
			vertices_ex[index - M - 1].normals.push_back(n);

			indices[indices_index++] = index;
			indices[indices_index++] = index - M - 1;
			indices[indices_index++] = index - M;

			a = vertices[index].pos;
			b = vertices[index - M].pos;
			c = vertices[index - M - 1].pos;
			ab = b - a;
			ac = c - a;
			n = cross(ab, ac);

			vertices_ex[index        ].normals.push_back(n);
			vertices_ex[index - M    ].normals.push_back(n);
			vertices_ex[index - M - 1].normals.push_back(n);
		}
	}