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tparkin

Triangles disappear on ATI video card

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I've never really had this problem before but yesterday I made a simple heightmap terrain the way I've always done. When I render it it looks fine until I rotate around some of the triangles and they begin to disappear or become translucent. This happened on my Mobility Radeon 9200 and a RADEON 9700 PRO but does not happen on a GeForce 6800 or a GeForce FX 5700. I was told this was a problem with ATI cards (which is why I mentioned it does work on Nvidia cards) and that there is a patch to fix this problem, is there? Here's a picture demonstrating my problem: http://ggnore.com/ati1.jpg Thanks in advance.

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Have you got the latest drivers for both pieces of hardware? If not, try those out.

Failing that, can you create a repro-program you could send to ATI? As long as you try and make it simple for them by giving a to-the-point repro and precise details they'll often let you know if its something they're aware of...

hth
Jack

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Guest Anonymous Poster
Sounds like backface culling to me, although I'm not sure why some cards would be performing it differently than others...

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When I try to install the latest catalyst drivers from ATI's website I get an error "INF error. Video driver not found". Then it tells me to install a standard VGA driver before running this installation. Which I have so what the hell? Maybe that's the problem, but how do I get the latest drivers? I'm not sure if the person who tested this on the RADEON 9700 Pro had the latest drivers or not.

Thanks for the quick replies.

Edit:
I don't think it has something to do with culling but I could be wrong. If anything it looks to me like a depth testing issue. Some triangles that are behind triangles in the foreground are drawn overtop of the foreground triangles. Look at the picture I posted. I could see it being a depth buffer issue but I'm not sure how or why and what difference NVidia vs ATI makes.

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Yes, I have created and enabled the depth buffer. Thanks for the reply.

I have just learned about a tool "ATI dhmod" which is supposed to allow you to install the latest catalyst drivers on a laptop (I'm on a laptop) but after trying it I still got the "INF error. Video driver not found" problem.

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I was just giving this some more thought... and I do remember that my work laptop (ATI-7200 I think) did random things like drop 1/2 the triangles on my shadow rendering demo.

If you've got time maybe you could double-check it against the code (From this article) I noticed a similar problem with...?

If you get some similar artifacts I'd be inclined to, at least for the laptop, go with a driver/hardware problem - as annoying as that might be [oh]

Jack

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I had a similar effect when I used a feature that wasn't available...
(I used indexbuffers on a card that didn't had these...)

Cheers

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That shadow demo seems to work fine for me. I didn't notice any problems.

Whenever I create anything I catch the result and check for errors. If I was using anything that didn't exist I would expect an error and my logfile would show it. (or so I hope!) This is a very strange problem.

Edit: I just simplified my program and got rid of the index buffer. I STILL have depth problems. I'm starting to think it's my old drivers but not sure how I can update to the latest ones given the error I get when I try to.

[Edited by - tparkin on July 28, 2005 3:34:54 PM]

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Just a quick aside..

Quote:
Original post by tparkin
Whenever I create anything I catch the result and check for errors. If I was using anything that didn't exist I would expect an error and my logfile would show it. (or so I hope!)

You would hope that was the case, and a lot of the time you will get errors and/or debug info... but there's just as many cases where it'll silently fail.

The demo I put in my journal a few days ago will allow me to set the "LOD" such that it generates far too many triangles for a single buffer/draw statement - yet there's no *error* that I saw - it just stops drawing them when they get to a certain limit [smile]

hth
Jack

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What version of directx do you have?

My lappy has the ATI mob rad 9200 and I havn't had any problems with it such as the ones you describe.
Try looking into the Omega drivers for your mobility radeon, they're made from the catalyst drivers but optimized for games and have optimized paths for mobility cards etc.
Make sure you read the FAQ/ReadMe before installing these drivers as you may (or may not) need to uninstall your previous ones (or something like that).

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