Carmack and Sweeney approve high ALU:TEX ratio, boo VTF

[Richdog]

Beyond3D interviewed Carmack and Sweeney about the latest ATI and NVIDIA architectures. Namely, how ATI has gone with 48 pixel pipes while NVIDIA is still keeping the 1:1 texture:shader relationship. Also, a bit of VTF.

http://www.beyond3d.com/

Unfortunately, this is only a news post, not a full-fledged article, so I can only link to the main page.

There are a few key points:

1. Contrary to claims made in the past, Unreal 3 does NOT CURRENTLY USE VERTEX TEXTURE FETCHING. It's official now, straight from Sweeney's mouth. Really though, the claim of U3 using VTF was never substantiated nor proven. Why did it spread so far?

2. Going with a higher ALU:TEX ratio is beneficial. Both gaming giants have confirmed this. Sweeney makes a snide comment about X1600 in the process. Or, could he be complimenting X1900? The NVIDIA-optimistic person would read this as saying that 7900 would have Sweeney's ideal ALU:TEX ratio, but I think that's a rather far-fetched stretch from what was actually said.

Since the release of ATI’s X1000 series of products we’ve seen a couple of different takes on Shader Model 3.0 from the two main vendors. The first caused a small controversy with NVIDIA clearly believing Vertex Texturing to be part of the VS3.0 specification, but ATI (and apparently Microsoft’s WHQL certification process) disagreeing such that this wasn’t included in the X1000 series, with “Render to Vertex Buffer” being provided as an alternative. Another divergence has been highlighted with the recent X1900 release and ATI keeping a comparatively low number of texture units in their high end, whilst scaling up their math processing capabilities significantly.

We’ve quizzed both id Software’s John Carmack and Epic’s Tim Sweeney on their thoughts on these differing directions between the two vendors:

In our interview with Eric and Richard of ATI they mentioned they went in the direction of tripling the ALUs versus the TMUs after talking with you for instance. My question would be: do you see this as a good direction? Are you working on shaders which require a lot of ALU while keeping TMU usage constant to today?

John: I think it is clear that the ratio of math to texture fetches is increasing.

Tim: It's a definite trend that ALU usage in shaders is going up at a faster rate than TMU usage, so it's reasonable that the hardware should increase ALU's faster than TMU's. What ratio is ideal is debatable; it depends on a whole lot of variables, but fortunately it's easy to see whose tradeoffs win at a given price level by running some benchmarks.


The X1000 series of ATI cards don't implement an actual texture fetch in the vertex shader, unlike NVIDIA's GeForce 6 and GeForce 7 series, preferring instead to get the texture information from a vertex buffer that the programmer has to setup in the pixel shader. Which implementation do you prefer?

John: For vertexes, I think more often about looking up data in a table rather than indexing an image, but I can see either perspective.

Tim: We don't use vertex texture fetch in UE3 right now, but I expect we'll be using it in the future for moving more of our displacement-mapped terrain logic to the GPU.

Tim also dropped the following comment to us with regards to Unreal Engine 3:

Tim: We'll be making a UE3 benchmark available several months before shipping UT2007 on PC, in order to encourage the hardware folks to optimize their drivers. We're not doing this now, because at our stage in development many aspects of our rendering pipeline aren't fully optimized, and if we encouraged IHV's to optimize for it now (by releasing a benchmark), they would end up wasting a lot of time optimizing code paths that aren't reflective of a final, shipping UE3 project. Regarding the timeline, we'll be actively developing Unreal Engine 3 throughout the current hardware generation -- all the way through 2009.

Thanks to Shadowmage at EOCF for that...

 

[Richdog]

lol in case anyone is wondering what the hell this is about it is basically two of the top games developer gurus saying that ATI's architecture is going to be more efficient than Nvidia's in future games.

I thought i'd at least get some responses to this

 

[ACESHIGH]

TBH i never thought it was an issue over how SM3 was supported on either manufacturers card, but their are always people who like to stir things up.

The fact that ATI's method of implementatoin is preferred on such a big game engine as UE3 should help validate ATI & also help gain some extra performance one would imagine. Nice for those who own these cards.

 

[D.P.]

lol in case anyone is wondering what the hell this is about it is basically two of the top games developer gurus saying that ATI's architecture is going to be more efficient than Nvidia's in future games.

I thought i'd at least get some responses to this

I think you should put your glasses on!

Apart from this being old news you have read it all wrong.

Texturing is going to be the biggest thing with Johns next engine, using the Mega Texturing technology he is pimping, but that is not to say Maths use is not going to increase as well.

And you have read the VTF completely wrong. Both Tim and John state that VTF is going to be important! Johns says he prefers to index a table than use render to VB. And Tim clearly states they will be using VTF in the UE3 engine to improve the terrain engine.
It is also interesting that the X1900 supports VTF, I wonder why

 

[D.P.]

TBH i never thought it was an issue over how SM3 was supported on either manufacturers card, but their are always people who like to stir things up.

The fact that ATI's method of implementatoin is preferred on such a big game engine as UE3 should help validate ATI & also help gain some extra performance one would imagine. Nice for those who own these cards.

How do you get to that conclusion. Sweeny states that they will use VTF!

Read this sentence again:
"We don't use vertex texture fetch in UE3 right now, but I expect we'll be using it in the future for moving more of our displacement-mapped terrain logic to the GPU."

I.e., the terrain engine will be made more efficient and faster by moving more of it to the GPU through the use of VTF.

 

[Richdog]

I think you should put your glasses on!

Apart from this being old news you have read it all wrong.

Texturing is going to be the biggest thing with Johns next engine, using the Mega Texturing technology he is pimping, but that is not to say Maths use is not going to increase as well.

And you have read the VTF completely wrong. Both Tim and John state that VTF is going to be important! Johns says he prefers to index a table than use render to VB. And Tim clearly states they will be using VTF in the UE3 engine to improve the terrain engine.
It is also interesting that the X1900 supports VTF, I wonder why

Rolleyes smileys make you really cool, use them more please I like them.

I'm no expert on the subject that's just how I interpreted it, if I read it wrong wrong then wow... I read it wrong. Don't give yourself a heart-attach kiddo...

 

[vapor matt]

Hi richdog hows it going mate!

Well iam pleased i got me a X1900 XTX card, but iam sure things will swing backwards and forwards between Ati & nv

The comeing months should be intresting but as allways there will be a new batch of cards on the horizon!

 

[D.P.]

Rolleyes smileys make you really cool, use them more please I like them.

I'm no expert on the subject that's just how I interpreted it, if I read it wrong wrong then wow... I read it wrong. Don't give yourself a heart-attach kiddo...

Why burst into here, making a huge post over nothing, highlighting unimportanting and misunderstood quotes if you don't understand what it all means.

What you said is the complete opposite of what is in that article.

I quote form the B3d comments :

Just Tim's little way of saying (without saying) that nvidia's way is better in his opinion.

It is impossible to know what exactl Carmack and Sweeny think anyway as they can't speak out openly.

The ALU:Tex ratio in the R580 is certainly not helping it much with todays games, thats for sure. And it is not as if the need for texturing is stationary, texturing is becoming more and more important, just that shader power will also becoem more important and is currently underpowered.

 

[Richdog]

Why burst into here, making a huge post over nothing, highlighting unimportanting and misunderstood quotes if you don't understand what it all means.

I didn't make the post, someone on another forum did, hence the "Thanks to Shadowmage" bit at the bottom.

As for "bursting in here" give me a break... I just posted something, and people make mistakes (though I am sure you never have). As I said... don't give yourself a heart attack... it's just graphics cards not life and death though sometimes you'd never think it. If it bothers you that much maybe you should go outside more?

Sheesh...

Hi richdog hows it going mate!

Well iam pleased i got me a X1900 XTX card, but iam sure things will swing backwards and forwards between Ati & nv

The comeing months should be intresting but as allways there will be a new batch of cards on the horizon!

Hi mate long time no see i'm well thanks... and yourself? Lucky git getting that X1900 card, i'd love one.

 

[Goksly]

Not sure about Sweeney, but isnt Carmack is practically bank rolled (TWISMTBP) by Nvidia? if so its not as if he is going to slate them...

 

[D.P.]

Not sure about Sweeney, but isnt Carmack is practically bank rolled (TWISMTBP) by Nvidia? if so its not as if he is going to slate them...

In a word, No, nor is sweeny.

They make games and engines and both companies recieve money from both ATI and Nvidia. So what. Its Pizza Man over at Valve who is in some kidn of finanical (and possibly sexual) relationship with ATI. The so claled 30 million dollar deal with Valve, shader day anyone LOL

 

[HighlandeR]

I think if anything Valve/Epic/idsoftware have shown they arent particularly biased towards graphic card producers and there all pretty direct. Obviously theres been times where they have been saying oh ATI are best or Nvidias better but there have been other times...

Think its too early to say as usual when the next gen cards ship all this will be water under the bridge as usual they both will have fixed or got the features

 

[D.P.]

I think if anything Valve/Epic/idsoftware have shown they arent particularly biased towards graphic card producers and there all pretty direct. Obviously theres been times where they have been saying oh ATI are best or Nvidias better but there have been other times...

Think its too early to say as usual when the next gen cards ship all this will be water under the bridge as usual they both will have fixed or got the features

Agreed, except for Valve, they have had an explicit deal with ATI although I think the relationship turned somewhat sour.

Epic and ID both get development money and they will both speak freely about what they like or dislike but neither will publicly critize an IHV.

This will definitely all be over come DX10- ATI (or NV) wont be able to get away without supporting the required features as this will be very strict.
With the features fixed then all there is to work on is implementation differences and thus performance.