/** Updates a cuboid-shaped region of the texture. Storage must be defined
beforehand. The image data must be in a format mathing the defined storage
and the update region must be fully inside the texture. */
void sub_image(unsigned level, int x, int y, int z, unsigned wd, unsigned ht, unsigned dp, const void *data);
/** Updates a cuboid-shaped region of the texture. Storage must be defined
beforehand. The image data must be in a format mathing the defined storage
and the update region must be fully inside the texture. */
void sub_image(unsigned level, int x, int y, int z, unsigned wd, unsigned ht, unsigned dp, const void *data);