Ah.. you want "decals" to appear on the walls when hit by a bullet. Did you allready figure out how to find the corrent position for the circle to appear (I think it's line/plane intersection)?

Another tricky thing is that if you use the same texture for alot of different walls, all the walls will show this black circle.

I'm sorry but i can't help you with this, because i never have done this myself and i never used GLScene.

You should search the forums (or google) with "decals" and you should find some articles on how to make them. I don't want to discourage you, but it might be way more difficult than you think.

Good luck with it. I really hope you can make this work.