OpenGL vs. Direct3D9 Performance issues

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mcaldwell
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OpenGL vs. Direct3D9 Performance issues

Post by mcaldwell »

Hello everybody,
First post. :) Let me just say that I am very impressed with what I have seen from Ogre so far. However, I have a question regarding OpenGL performance. I just installed the Terrain demo (as laid out in the absolute newbie's guide) and I get about 40fps when I run it using OpenGL and about 400fps when I use Direct3D. I guess I was expecting performance to be about even, not a 10x difference. Was I wrong in expecting this? Perhaps somebody could explain why this is happening. BTW, my system is an AMD 64 3000+ (2.2 GHz) with 1GB 400MHz RAM and a Chaintech nVidia geForce 5700LE vid card with 256MB VRAM.
Thanks. :)

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kulik
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Post by kulik »

That's strange .. What drivers have you got? What's your Windows version? Does this happen with all demos?

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DWORD
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Post by DWORD »

Very, very strange! And sorry I have to ask, but are you sure you didn't compare a debug and a release build? Otherwise it has to be a serious driver issue, I guess. :?

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sinbad
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Post by sinbad »

I'd say definitely an old driver issue. A couple of the older nVidia drivers had some serious performance issues with the GL extensions we use which were fixed in later versions. I have a 5900 and GL performance is very slightly under Dx9, but that's because of a known issue with the nVidia VBO implementation. It's not enough to get worried about though (5% ish iirc)

mcaldwell
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Post by mcaldwell »

DWORD: Yeah, I tested both Direct3D and OpenGL on the same build, so it is not a difference between builds.
Thanks a lot everybody, now I know that this is somewhat abnormal behavior. I will check to see if I can find some updated drivers and see if that fixes the problem.

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