Futuremark: 3DMark06

Why you won't do this is that four contiguous taps in your sparse filter are meaningless.

I'm talking about shadow map filtering after PCF - where PCF is a technique that's predicated on taking contiguous samples from the shadow map, and a technique that's hard to tweak for quality. Which is why 3DMk06 doesn't use PCF in tests graphics tests 3 and 4.

The technique presented by ATI in the Siggraph presentation (as well as other places) uses a sparse-sampled kernel in preference to a large-density PCF filtering technique.

From page 18 of the presentation linked above:

Multiple-contiguous sample taps don't make sense in a sparse-sampling kernel. At least, not as far as I can see.

Jawed


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It's why the X1k material showed a tree (with real geometrical branches) being shadowed when discussing DB performance.

Jawed

 

Compare and average are negligible overall is almost like saying shadow mapping itself is negligible overall, which we know it is not.
Shadow mapping only consists of three operations: sample, compare, average. And then the result is multiplied with the light color/intensity and passed on to the light interaction part of the shader.
PCF cobines those three into a single operation (though I'm not convinced it's single cycle [like point sampling is], which would be bandwidth limited anyway). Fetch4 accelerates sampling but does nothing to the compare and average steps.

Comparing four samples is a vec4 sub followed by a vec4 cmp, and averaging multple samples is a add4/dp4 cascade (unweighted, which in this case is fine).
So if Futuremark wanted to use fetch4 for the PS3.0 tests in 3DMark06 they would have had the controversial choice of taking x < 16 fetch4 samples to somehow match the average quality of 16 point samples, doing less texture sampling and more arithmetic.

Taking 16 fetch4 samples instead of 16 point samples would have increased quality but also the workload by 12 sub4, 12 cmp4 and 12 add4. In any case, they would have done the same for PCF, which actually means that, relatively speaking, ATI is better off with Futuremark not using Fetch4/PCF in the PS3.0 test at all.

 

When I said the compare / average for Fetch4 was likely to be fairly negligable I think we're looking at about 2 cycles on RV530 style hardware, some of which will be hidden by the instruction scheduling.

 

Well, I begin to live with the idea that 3DMark 2006 is just as is.
Looking on the bright side, X1800 users can test not just how their card will suck big time running future games, but they also can test how much worse it will perform with AA enabled.

 

Could we get a Mac version in the next release?

You know you want to.

 

Do we have a concensus that shadowing in graphics tests 3 and 4 is a level playing field for ATI and NVidia hardware?

Jawed

 

I don't understand why not either, Nick do you know?

 

As soon as MacOS X supports Direct3D and you have an Intel Mac.

 

Heh, hell froze over once already this year, if we're lucky it may just happen again.

 

Don't get me wrong, I do agree that Fetch4 and PCF should be used when available. However, it wouldn't have been as easy as saying "let's enable fetch4", because even if the three additional samples per fetch cost only half a cycle, that's going to be 8 cycles per pixel for a 16-sample sparse kernel. So Futuremark would have had to adjust the number of samples to somehow get comparable quality in all three paths. Which isn't always trivial.

btw, I also think that the decision to use either F4/PCF or a 4-tap rotated kernel in the PS2.0 test is somewhat poor in terms of comparable quality. However I'm not sure there's a better one. 3-tap maybe?
And the point sampling can be hidden by a sufficiently arithmetically complex shader, too.

 

Brilinear , 3d murk , clip planes ............. . And just generally poor iq , not because the cards couldn't look better , but because looking better wouldn't have been competitive .

 

Okay, I don't quite see how you'd call the first cheating. I also have no idea what you're talking about with "3d murk," but the third was, from what I remember, only done in 3DMark. You specifically were attempting to call attention to cheating for non-DX9 games.

 

Yet more irony:

3DMark 2006 will probably show X1900 to greater advantage than any other available benchmark.

 

Not true...."there is another".

 

the son of fudo?

 

Nice tease.

would have been even better with the dramatic pauses "There....is.....an...oth....errrr.

 

Dude, don't rip on Yoda. He was dying, man!

 

So what is different between the XT and XTX besides the few extra clocks?

 

I was wondering if the 3dmark rep could be so kind in explaining why rendering an entire 3d scene frame by frame using only the CPU is relevant to any kindof game. Thanks.