Stupid graphics question

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shaft
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Stupid graphics question

Post by shaft » Fri Apr 01, 2005 9:00 pm

I'm sure this is a dumb question but I'm not super fluent in GL or directX so I thought I'd ask.

Is triangle-face culling performed within openGl or atleast the ogre "rendersystem" class? More specifically, ogre scene managers cull at the object level, not the triangle-face level. Once the potentially visible objects are selected for rendering, its in openGL, or the hardware that optimizes the rendering of those triangles correct?

The reason I ask is I've been reading about various culling techniques (I'm doing something at the object level), and most of the articles talk about culling at the geometry level. I then begin pouring through the Ogre source code, and it looks like the scene managers are culling at the object level, and I haven't really seen anything that does culling at the triangle-face level.

Is my understanding correct?


Thanks,
Jeff
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sinbad
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Post by sinbad » Fri Apr 01, 2005 9:33 pm

Yes, GL and D3D both eliminate offscreen and back-facing triangles in hardware during primitive construction.

Culling at the triangle level in software went out with the 90s ;)
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shaft
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Post by shaft » Fri Apr 01, 2005 10:03 pm

Good to know the graphics class I took in college is already obsolete (atleast one of them is obsolete).

Thanks again.

-Jeff
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jacmoe
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Post by jacmoe » Fri Apr 01, 2005 10:11 pm

No, it isn't! :)
It is valuable to know what goes on, even if it's going on in hardware, if you want to understand and use it better. :wink:
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temas
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Post by temas » Fri Apr 01, 2005 10:24 pm

jacmoe is just trying to make you feel better, it's useless :twisted:
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Sydius
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Post by Sydius » Sat Apr 02, 2005 12:12 am

Knowing how it does something is important if you want to know what it will do in situations you do not actually test. Not to mention, it helps you plan things out to be more efficient.
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Post by lodi » Sat Apr 02, 2005 2:13 am

Well, 'knowing how it does something' is all well and good, but trying to optimize based on antiquated knowledge is one of the worst things you can do. That's the kind of thinking that lands you writing a ROAM engine thinking you're doing something to increase performance ;-)
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