쥔장, 이 코드 킵 .. (기저 벡터를 통한 회전)

  ...

  const zaxis = dir.negate().normalize().toConst();
  const xaxis = cross(vec3(0, 1, 0), zaxis).normalize().toConst();
  const yaxis = cross(zaxis, xaxis).toConst();

  const mat = mat3(
    xaxis.x, yaxis.x, zaxis.x,
    xaxis.y, yaxis.y, zaxis.y,
    xaxis.z, yaxis.z, zaxis.z
  ).toConst();

  const finalVert = modelWorldMatrix.mul(mat.mul(positionLocal))
    .add(positionStorage.element(instanceID)).toConst();

  return cameraProjectionMatrix.mul(cameraViewMatrix).mul(finalVert);
}