Animation - Erasing a Sprite

no-reply@allegro.cc (Deus Ex Machina) — Tue, 16 Oct 2007 00:47:55 +0000

Hi,

I was wondering if anybody could expain this:

To keep it simple, say I want to move a 10 x 20 rectangle around on the screen. If I try to erase it with a 10 x 20 rectangle of the background color, I get a "trail" in the path of motion.

I can deal with this okay by making the erasing rectangle a bit bigger, but it doesn't make sense to me logically. If I draw a rectangle of the background color of exactly the same size, in exactly the same place the moving rectangle was, shouldn't it obliterate it?

Thanks,

Jim

no-reply@allegro.cc (Paul whoknows) — Tue, 16 Oct 2007 00:54:19 +0000

If my understanding is correct, a double buffer system is what you need.

no-reply@allegro.cc (Neil Black) — Tue, 16 Oct 2007 01:03:02 +0000

Are you moving it before erasing? Make sure you're erasing the right spot.

no-reply@allegro.cc (Slartibartfast) — Tue, 16 Oct 2007 01:23:11 +0000

Make sure you Erase->Move->Draw->Render.
Also, you're drawing and erasing to a single bitmap, right?
And if you can't fix it yourself, some code might help. (using [ code ] tags and showing only relevant code)

no-reply@allegro.cc (Neil Black) — Tue, 16 Oct 2007 01:25:34 +0000

Quote:

Make sure you Erase->Move->Draw->Render.

Yeah, that's what I was trying to say.