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    ATi Doom 3 Hack/Fix


    Cyb

    Saw this on Ye Ole Forums. For those of you with ATi cards check out this here post which will hopefully speed up Doom 3's performance on your ATi card by up to 40%. Note that if you have an NVIDIA card this won't work (in fact it will make the game slower), so only try it if you have a Radeon. Also it's important to back up your pk4 files and such first as this will probably break multiplayer. Worth a shot if you want some extra fps.

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    Nvidia cards... is there a tweak guide/file available? Or is the code really optimized for those cards like stated so that you wont gain anything more than a couple of frames!? ;)

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    Chris Hansen said:

    Nvidia cards... is there a tweak guide/file available? Or is the code really optimized for those cards like stated so that you wont gain anything more than a couple of frames!? ;)


    You don't really get more than a few frames with this tweak. The tweak makes a small alteration to a shader, but the results aren't 100% the same as the old code (some artifacts).

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    udderdude said:

    The artifacts aren't really noticeable unless you're being anal .. all I want is more FPS dammit! :P

    Then get a new computer.
    I just need a new GFX card, my old GF3Ti "failed it"... the CPU, AMD K7 3000+, should be enough.
    (Should try this game in software render :P )
    Or wait for the linux version, as it is normal that games run faster on a unix, as a unix isnt such a resource hog like a nt.
    Unless you have 10 million daemons up and running.... but then you would have a webserver ;)

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    Szymanski said:

    You don't really get more than a few frames with this tweak. The tweak makes a small alteration to a shader, but the results aren't 100% the same as the old code (some artifacts).


    Ahh, I see. Well, as long as there isn't a great percentage to be gained in performance, then I'll just play as-is.

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    If you have a lower-end ATI card like my 9600xt, probably the best thing I've found to increase performance is to go to your ATI advanced options in display properties, customize your gl/dx9 properties to pure performance. Not as pretty really, but still sexier than Quake 3 and runs a lot smoother. I've been running in low quality at 640x480 but the game is still very playable (unlike "Quake 1 at 320x240 on a 486" which basically looks like a college dorm toilet at 6 o'clock on a saturday morning).

    Any new maps out for D3 yet?

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    the guy tweaking the shaders is not a genius. You can find these informations in iterview with John. He speaks about functions that affects the shaders (textures, surfaces...) and about lookup table. Nothing surprising;)

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    Having actually read some of the thread, it appears that the benefit from the tweak only really kicks in if you have anisotropic filtering set in the ATI control panel applet.

    If you have AF set from in-game and "application preference" set in the control panel it doesn't really help much.

    Anyway, it's an issue with how ATI does their drivers and they'll probably issue a fix for it ... although it's at least partly the Doom 3 engine's fault for using lookup tables when a calculation would be more elegant.

    Cards that couldn't handle the calculation probably need to be in another rendering path anyway.

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    Lookup tables are faster than using a function and recalculate values every time its needed. You spend too much time in this function. May be except if using a bit shift and calculate exponentialy (pow() function). There is a reason for using tables - optimization. ATi can reach better performance only by rewriting the drivers. I think here's something strange in ATi. If they have so powerful hardware, why they don't show its power from start? Why they have to wait for engine that pushes their drivers on the edge and then write new drivers... Some kind of marketing strategy? Some kind of optimalization? Do we need new drivers for every new title?
    ATi is very strange company.

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    Lookup tables are not necessarily faster, as Carmack himself indicated in the Beyond3D interview that he might have reconsidered it had he known how long it would take Doom 3 to come out back when he was writing that bit of code.

    In fact it's theorized that Nvidia has been using shader-replacement conversion code in their drivers all along and since the 44.xx days, which is going to be a major part of why they have a slight performance edge over Ati with their high-end cards at Doom 3 at this point.

    If you didn't know exactly how much and in what way any new game will push your hardware, it'd be pretty hard to optimize directly for it eh?

    Both Nvidia and Ati tweak their drivers with every release for performance. The next set from Ati will be no different in that respect.

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    Does it mean that hardware vendors don't know how is their hardware powerful? They make only a particular optimalization. Does it mean that if you want to play D3 and HL2 on the same hardware you have to use different drivers version? OK, John could write it in another fashion, but earn is only few frames per second. There's no reason for use rough power. Still cannot catch the point...

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    goddard said:

    Does it mean that hardware vendors don't know how is their hardware powerful? They make only a particular optimalization. Does it mean that if you want to play D3 and HL2 on the same hardware you have to use different drivers version? OK, John could write it in another fashion, but earn is only few frames per second. There's no reason for use rough power. Still cannot catch the point...

    It means that the hardware and the software related are sufficiently complicated that you cannot simply blindly write code at it and expect it to work faster.

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    goddard said:

    Why blindly? Everything is complicated. But what about the D3 and HL2? What do you think?

    No, not two gfx drivers, but a driver that detects the games and uses the routines needed for that game.

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