GeForce 3 tech question

[grit621]

I understand that the GeForce is a programable card, and the "language" used to program the card is generic to the hardware (maybe I phrased that poorly?)? Thus, the result is any new programable card can run one of the new DirectX 8 or OpenGL (doom3) games? Is that correct?

What happens when someone trys to play a game (like Doom3, et al.) designed to make use of the GeForce3 features, but they have an older video card (eg, GeForce2)? Will Doom3 be playable on older video cards? Will ANY games that make use of the GeForce3 features be playable on older cards? What will the games look like?

Just wondering, because I'm really impressed with the preliminary screen shots, but I can not/wont justify more than $300 for a video card.

[SlartyB]

Originally posted by grit621:
I understand that the GeForce is a programable card, and the "language" used to program the card is generic to the hardware (maybe I phrased that poorly?)? Thus, the result is any new programable card can run one of the new DirectX 8 or OpenGL (doom3) games? Is that correct?

What happens when someone trys to play a game (like Doom3, et al.) designed to make use of the GeForce3 features, but they have an older video card (eg, GeForce2)? Will Doom3 be playable on older video cards? Will ANY games that make use of the GeForce3 features be playable on older cards? What will the games look like?

Just wondering, because I'm really impressed with the preliminary screen shots, but I can not/wont justify more than $300 for a video card.

I am a hardware expert, not an API expert, so maybe Humus can back me up here, but I think it's all magically handled in the API. One of the first things that happens is that the API will ask the card what it can do. If it can't do some of the things that it needs to do for the particular DX implementation, then the feature is emulated in software.

This is what allows you to have a common API with vastly different hardware. The conversion of generic API calls into hardware specific functions is handled in the driver.

So, your GF2 will play DX8 games (you will - of course - have to download DX8 from MS), *BUT* if you turn on all the new DX8 features, it will probably be unplayable because the framerate will be crippled by the software having to do a lot of the new "eye-candy".

[Iceball_AARF]

The games should be playable, if you turn off the features that "need" a geforce3 card. If you don´t then it´ll be emulated by software, at least in most API´s, and it´ll be reeaaaallyyyyyyy sloooooooow.
"Terry" posted some days ago this link: http://www.rivastation.com/index_e.htm
Here you can find how to emulate a geforce3 in any geforce2 so you can try the new nvidia demos & see how slow it can get.

[Humus]

SlartyB is partly correct and partly incorrect. Some features are handled in software if there's no hardware to back it up, but that's just features that are somewhat "realistic" to implement in software. If features for example is missing in the rasterisation process (say that it misses DOT3 bumpmapping for example) it would mean that the rasterisation pipeline in the hardware cannot do anything, the software rasteriser takes over completely. So, in such cases there is instead a way in DirectX to ask whether the hardware supports a specific feature or not. If it doesn't, well, then it's up to the application to either find another way to do it, disable the function completely or just tell the user that it cannot run since the hardware doesn't support the needed function.

Doom3 is most likely going to be an OpenGL game as all other id games. That means that Doom3 will look for OpenGL extensions for the shaders (GL_NV_texture_shader and GL_NV_vertex_program). I highly doubt that they will completely drop support for legacy hardware, so if those extensions isn't present, it'll need to look at other extensions and do the effects as good as it can. It'll simply mean that other cards will be missing some effects. I think it's a safe bet to say that Doom3 will at least run on GF1 and higher, the performance is though another question.


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[SlartyB]

Originally posted by Humus:
SlartyB is partly correct and partly incorrect. Some features are handled in software if there's no hardware to back it up, but that's just features that are somewhat "realistic" to implement in software. If features for example is missing in the rasterisation process (say that it misses DOT3 bumpmapping for example) it would mean that the rasterisation pipeline in the hardware cannot do anything, the software rasteriser takes over completely. So, in such cases there is instead a way in DirectX to ask whether the hardware supports a specific feature or not. If it doesn't, well, then it's up to the application to either find another way to do it, disable the function completely or just tell the user that it cannot run since the hardware doesn't support the needed function.

Doom3 is most likely going to be an OpenGL game as all other id games. That means that Doom3 will look for OpenGL extensions for the shaders (GL_NV_texture_shader and GL_NV_vertex_program). I highly doubt that they will completely drop support for legacy hardware, so if those extensions isn't present, it'll need to look at other extensions and do the effects as good as it can. It'll simply mean that other cards will be missing some effects. I think it's a safe bet to say that Doom3 will at least run on GF1 and higher, the performance is though another question.

Thanks Humus. Hey! I was almost right

Maybe I should stick with hardware specific stuff ....

[Drakh]

Originally posted by Humus:
I think it's a safe bet to say that Doom3 will at least run on GF1 and higher, the performance is though another question.

I think Carmac said somewhere, that a GF2 GTS would be the absolute min spec to run DooM3, in low resoulution of course.


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