code: func (at AttrType) Size() int {
  	switch at {
  	case Int:
  		return 4
  	case Float:
  		return 4
  	case Vec2:
  		return 2 * 4
  	case Vec3:
  		return 3 * 4
  	case Vec4:
  		return 4 * 4
  	case Mat2:
  		return 2 * 2 * 4
  	case Mat23:
  		return 2 * 3 * 4
  	case Mat24:
  		return 2 * 4 * 4
  	case Mat3:
  		return 3 * 3 * 4
  	case Mat32:
  		return 3 * 2 * 4
  	case Mat34:
  		return 3 * 4 * 4
  	case Mat4:
  		return 4 * 4 * 4
  	case Mat42:
  		return 4 * 2 * 4
  	case Mat43:
  		return 4 * 3 * 4
  	default:
  		panic("size of vertex attribute type: invalid type")
  	}
  }
docs: // Size returns the size of a type in bytes.