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POINT SPRITE problem?

Started by livingaftermidnight Aug 31, 2005 at 10:23 AM 2 replies 1.3k views

Original Post

Aug 31, 2005 at 10:23 AM

Hello, I wrote this particle engine for my game and it works on most computers with either NVidia or ATI cards installed. The test machine that we are running our game on, does not. It only renders a few of the particles. I can't understand why it would do this. I've tried setting GL_POINT_SPRITE_R_MODE_NV to GL_ZERO, didn't work. I don't have GL_POINT_SMOOTH enabled. I don't get it. The computer has the .net framework installed, and the latest ATI Radeon 9800 PRO drivers. Here is a link to my particle engine. http://www.willdull.com/files/ParticleEngineDemo.zip

Eric Lengyel

108

Eric Lengyel

Aug 31, 2005 at 2:19 PM

The ATI drivers have had severe problems with point sprites for several years now. (Btw, ATI hardware doesn't support GL_POINT_SPRITE_R_MODE_NV.) Also, some hardware features are disabled if you enable point sprites (e.g., you can't access fragment position in a pixel shader). Your best bet is simply not to use point sprites on ATI hardware at all and instead send it billboarded quads.

On Nvidia hardware, point sprites work beautifully and are nicely orthogonal to the rest of the hardware.

livingaftermidnight

Author

livingaftermidnight

Aug 31, 2005 at 5:55 PM

Thank you for your response. My laptop currently runs with an ATI Mobility Radeon X300 series and my particle demos run on it fine. In fact, I developed it on that card. So some ATI cards work but others don't. So I figured it's a driver problem.

Tomorrow, I'm going to convert it to billboarded quads and see how it runs. Thanks again and congrats, as you are a very accomplished programmer.

Will

ph33r

Aug 31, 2005 at 11:33 PM

I've actually had different experiences where ATI cards worked well with point sprites and NVIDIA didn't support them.

To solve this problem in directx, if the card did not support psprites I would switch to software vertex processing. After I rendered the particle system I would switch back to hardware vertex processing. The software emulation of vertices works fairly quickly, expecially for a particle system. I'm not sure if there is some sort of state you can set in opengl but it is worth looking into.

- Dave

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