/** Updates a rectangular region of a face. Storage must be defined and
allocated beforehand. The update region must be fully inside the texture.
The data format must be compatible with the defined storage. */
void sub_image(TextureCubeFace face, unsigned level,
int x, int y, unsigned w, unsigned h,
/** Updates a rectangular region of a face. Storage must be defined and
allocated beforehand. The update region must be fully inside the texture.
The data format must be compatible with the defined storage. */
void sub_image(TextureCubeFace face, unsigned level,
int x, int y, unsigned w, unsigned h,