texture conundrum (dynamic textures, orthographic mode, ...)

I'm trying to do some demo effects with dynamic textures.  Only I'm really screwing up, somewhere.  The code is nowhere near clean, but it's all in one little c file (god bless tetris clones, eh?).

I'd really appreciate any help you could toss my way.  I've read a dozen squared tutorials on this and that sorta related thing, and am seriously sleep dep'd at the moment.  Umm.  Right, the code: http://erif.org/temp/fallingup.c

One of the main issues seems to be that after I'm writing to the texture, and displaying it on the screen, what was in the texture gets wiped entirely.   i want instead to "fade" what was there ... yeah, just really confused.  Thanks (and of course, some points...) for any help.Start Free Trial