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galaxist

About Hardware T&L with Direct3D

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I noticed quite a while ago that some Direct3D games insist to run on system with hardware T&L only. Although most graphics chips nowadays support hardware T&L, but there are still some of it, such as Intel GMA950/900 are not equipped with hardware T&L. I've spent hours trying to search the answer by using google but got nothing. Is it because those game developers did some special optimizations for something?

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These cards do work a bit backwards. When more powerful videocards first emerged, 3D T&L was the main job they had to do. So historically just about all cards have had hardware T&L (i.e. hardware for vertex shaders). Nearly all of the current (gaming) cards also still have hardware T&L, simply because this specialized hardware is much faster than emulating it in software on the CPU. When Intel designed the GMA's as budget cards though, I think they figured they might as well do the T&L in software, since the heavy load had already moved from vertex processing to pixel processing. That'd be why the GMA supports hardware pixel shaders, but no hardware vertex shaders.

The problem is that before the GMA, one could assume that if a card didn't have hardware T&L, it was pretty much a rubbish card that's probably lacking other features needed to support your game. Making a game 'work' with the GMA however it typically just a matter of setting a flag in the code, indicating you'll settle for software vertex processing if hardware is unavailable. This may be overlooked, but the GMA also really isn't that great a card and IMO it's not very suited for 3D games anyway, so the developers leaving out this flag might just be plain intentional.

Hope this is correct :)

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