Thanks, thats exactly what I'm looking for. Volatile images seem kind of a hassle... at any moment the VRAM may be reclaimed, meaning if you had a separate
thread perform the rendering, you have to instantiate and run it again (though I guess you could have a buffered image snapshot , but I'm don't know about performance issues and trade offs - is it better to redo the rendering on the volatile image and have that drawn to the screen, or to have a buffered image snapshot made during initial rendering, and have that drawn to the screen if the volatile image needs to be rerendered...).
Andy