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Old 07-31-09, 10:05 AM   #21
ChrisRay
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Default Re: EQ2 Shader 3.0 upgrade

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I'll hit the rest of your post a little later. But these portions are pretty laughable. The reason PP wasn't exposed in HL2 has NOTHING to do with performance benefits. Of course PP has performance benefits.
Minor Performance benefits. Which created issues with glass shaders. If you don't believe me. Take tommti's 3D Analyzer software. And Force "PP" flag on all shaders in Half Life 2. You will set a speedup. But its roughly in the range of 5% and created rendering areas with places like "glass" shaders.

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Anyways NV35 "did" force pp in HL2
The NV35. Aka Geforce FX 5900 uses DirectX 8.1 as its default renderer for HL2. It Always has. I wasn't talking about the Geforce 5 cards was I?

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bout 6800. I even provided the links (beyond3d links in my 1st post). The 6800 was FP32 throughout the pipeline. However PP alleviated some register pressure on the 6 series, and freed up ~30% performance, depending on the shader (some received no benefit)
Yes. In a full throughput test where the primary bottleneck was registry performance. The Geforce 6 series could lose somewhere to 30% performance using FP32. However this is a "Synthethic" test. IE. It doesn't take into account that no shader is designed to "Run" like these ones in modern games. Shaders pass through pipeline and then another comes through the pipeline. These specific tests are designed to run the same shader code through the GPU pipeline repeatively as a benchmarks. Its not a real world result. This is why you never saw this kind of performance deficit using FP32 verses FP16. The performance benefits in Half Life 2 were not there.

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Here is a bit on DX9.0 and partial precision: http://www.beyond3d.com/content/interviews/23/
And your point? I was not arguing that partial precision was good or bad. I said that the performance impact on Geforce 6/7 hardware not large when moving from FP16. Especially compared to Geforce FX. Everyone knows the Geforce FX did not have the registry space to run DirectX 9.0 shaders in FP32 fast. Let alone FP16. The Nv35 in comparison to the NV30 did replace 2 of its integer units with FP units. But was still confined by registry making it unable to cope with heavy registry usage.

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Minimum Dx9.0 was always considered S16e7. Ok? PP is an nVidia addition to the spec, which Microsoft allowed.
Thats not what you said. You said PP is not a part of DirectX 9.0 spec. That is wrong. Partial Precision is infact a part of all recent DirectX 9.0 builds. And has been since the debut of the Geforce FX. Yes it may not have originally been intended for DirectX 9.0 specification. It was however updated to be included. I am not saying otherwise either.

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It was always clear this was an extension to MS spec at nvidia's request, and not orthodox Directx 9.0. Anyways, like I said, I don't particularly care what you believe.

See unlike you, I enjoy facts!
There is nothing "non factual" about what I said. SM 3.0 was not initially a part of DirectX 9.0 spec either. The fact is. PP is and has been a supported standard for the majority of time DX 9.0 accelerators have been available. Yes it may have been changed. That doesn't change that your initial comment about PP "Not being DX Spec" was wrong. Because it is a part of baseline DirectX 9.0 spec. Before SM 2.0A, Before SM 2.0B, And Before SM 3.0. You seem to suffer a major point of confusion regarding the Geforce 5/ Geforce 6, Geforce 7, and Geforce 8 series. All which behave very different when operating FP16 or higher calls. You do realise that all your links have done is reinforce my original point?

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Nvidia had no problems with its SM3.0 implementation.
This is wrong. There were some drawbacks to Nvidia's SM 3.0 implementation. Firstly its Dynamic Branching performance was insufferably slow and unusable. Hence why anything that used SM 3.0 was using Static Branching. ((See Far Cry SM 3.0 implementation. ATI even did a whole campaign of the HD1900XT to where they stated they did "SM 3.0 Right" because their dynamic branching granularity was much better than Nvidias. As well as supporting HDR with AA. ((Though HDR was not specific to SM 3.0)). It wasn't until the Geforce 8 that Nvidia actually supported AA + HDR via the ROPS.
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