PDA

View Full Version : point size limit?



andras
01-27-2006, 03:36 PM
We are using point sprites to render icons in our 3D scene, because it's much easier and more efficient than traditional billboards. Unfortunately I've just realized that there's an implementation dependent maximum size for points. In our case it seems to be 64x64 on the GF6600. Now, this is probably big enough for particles, but it's a severe limitation, when using point sprites to render hi-resolution icons. I'm wondering if there's any reason for such a limitation?

Is this something that can be changed in the driver or is this a HW limitation? Do we have any chance of seeing larger points on this HW any time soon? (BTW: we are using non-antialiased points)

Thanks,

Andras

PS: I'm not sure if posts like this should go in the advanced forum, but I don't know where else? Maybe we should have a forum dedicated to driver/hardware/support questions?

dorbie
01-27-2006, 04:10 PM
There are technical implementation reasons for the limit (interpolator & size precision etc) but of course a driver could emulate with quads, then again it's a catch 22 scenario because you can't know the size in advance.

You may want to send quads to a vertex shader with attribute information for your custom transformation.

You lose the bandwidth advantage of points (the reason good drivers don't do this) but you will at least benefit from hardware accelerated transformation and billboarding.

If you have a way for your application to 'know' whether a point or set of points was going to be large with trivial bounds or range tests (round robined etc. as an optimization), then you can combine the techniques and get the best of both worlds.