[SDL] DirectX 7?

David Olofson david.olofson at reologica.se
Mon Sep 30 07:21:00 PDT 2002

On Friday 27 September 2002 03:52, David Moffatt wrote:
> What about being able to move graphic data to the video card
> periodically. Will this incur a speed hit?

Well, the data does have to be transferred over the AGP - and by now, I 
think we all know what that means if there's no busmaster DMA. It *could* 
be relatively slow on some platforms and/or drivers, so better not rely 
on it being any faster than s/w rendering into VRAM.

> I have many specialised graphics routines which wouldn't be covered in
> SDL's API (not just alpha blending). For example I am able to replace
> one colour group with another to reduce the number of animations that
> have to be loaded.

That sounds like something you *definitely* should not do in real time, 
unless you're low on texture RAM. Sounds like a typical load time thing 
to me, in fact.

Any other examples?

Either way, I think you can still rely on texture uploading speed being 
sufficient for at least some 70,000 pixels per frame, and unless you need 
insane amounts of graphics, prerendering stuff and uploading it to 
texture RAM should go a long way, especially if there's fast alpha, 
additive and subtractive blending as well.

//David Olofson - Programmer, Composer, Open Source Advocate

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