No Displacement Mapping Support in GeForceFX

[GTaudiophile]

This according to Reactor Critical:


We were very astonished when Nvidia decided to turn off the parametric surfaces (or RT-patches in the DirectX parlance) support in their GeForce3 drivers a year ago. When asked why, Nvidia officials told that the support of curved surfaces should be turned off because several game developers implemented ATI?s TruForm technology in their games and the software decided that the GeForce3 accelerators also supported the N-Patches, whereas the GPU just tried to emulate them through RT-patches causing the performance to drop dramatically. Since the higher order surfaces are not used widely these days, their support is not something the end-users can take any advantages of, we forgot about this fact shortly after it had been revealed.

The higher order surfaces are here to allow game-developers to create very complex 3D-models without using too many triangles. There are many approaches of creating HOS surfaces, however, there are only two of them on the consumer market: RT-Pathes and derivatives and N-Patches in different incarnations. RT-Patches require control points definition over a surface at the stage of creating a model. Another way to achieve complex models and environments is to utilise N-Patches and its derivatives that calculate the control points on-the-fly. Since the latter were introduced by ATI, Nvidia said that they were not going to implement this in their own chips.

What is even more interesting is that they decided not to support Displacement Mapping technology from DirectX 9.0 due to unknown reason, according to sources. Maybe because the approach is based on the notorious N-Pathes?

Microsoft wants IHVs to support Displacement Mapping and points it out in every document they issue in regards DirectX 9.0. Both ATI Technologies? RADEON 9700/9500 VPUs and Matrox Graphics? Parhelia 512 graphics processor support the Displacement Mapping.

I now wonder if Displacement Mapping is ?must be? function of the DirectX 9.0. If it is, Nvidia may not be able to claim the DirectX 9.0 full hardware support for the GeForce FX VPU.

 

[Thor86]

Damn, you beat me to it, but I posted in the Video forums. 🙂

 

[Rand]

Tis' unfortunate isnt it?
I believe it was nVidia's Doug Rogers that first revealed the lack of displacement mapping support in the NV30 a few days ago.

I now wonder if Displacement Mapping is ?must be? function of the DirectX 9.0. If it is, Nvidia may not be able to claim the DirectX 9.0 full hardware support for the GeForce FX VPU.

Displacement mapping is a technology included in DX9, similar to EMBM was a technology included in DX6, and vertex shading in DX8. It is however most definitely NOT a physical hardware requirement. nVidia is under absolutely no requirements to have displacement mapping capabilities to proclaim full DX9 compliancy.

They've done similarly in the past by not supporting EMBM until DX8... two generations after it initially appeared.
SiS Xabre is able to proclaim full DX8.0 compliancy despite a lack of hardware vertex shading capabilities... as vertex shaders are merely exposed in DX8, but not hardware requirements. (Pixel Shaders however are required)
Another quick example is HigherOrderSurfaces... an option exposed in DX8, thge GeForce 3/4 line lacks HOS capabilities.... but is still fully DX8 compliant.

FWIW, next generation hardware with Vertex Shaders 1.3 should be able to do displaccement mapping directly in the vertex shaders... though this wouldnt be a preferable solution.
Current revisions of VS don't support texture sampling in the shaders directly, which would be required for displacement mapping though.... as said, that's not scheduled until VS 3.0


It's a feature I'm strongly in favor of seeing utilized in mainstream gaming... but without wide-spread hardware support it'll likely never see much usage.
It's perhaps not the ideal long-term solution but it should be an excellent technology for the next 3yrs or so.
DM still has room for improvement though, at the moment I really don't consider it a good alternative/extension to/of bump mapping for characters.
It's excellent for terrain though...

 

[Rand]

You know... come to think of it, I'm surprised nVidia didnt comment on their ability to do pre-sampled displacement mapping... VS 2.0 working in combination with the processor can do that pretty easily, and I wouldnt imagine it'd take much effort at all to implement in the drivers.
Then again... pre-sampled DM is extremely limited and inflexible and won't work with adaptive tesselation do it isnt exactly worth a damn.

Mildly surprsing nVidia didnt mention it to at least say they can support some form of DM.

 

[Mr.IncrediblyBored]

Originally posted by: Rand
You know... come to think of it, I'm surprised nVidia didnt comment on their ability to do pre-sampled displacement mapping... VS 2.0 working in combination with the processor can do that pretty easily, and I wouldnt imagine it'd take much effort at all to implement in the drivers.
Then again... pre-sampled DM is extremely limited and inflexible and won't work with adaptive tesselation do it isnt exactly worth a damn.

Mildly surprsing nVidia didnt mention it to at least say they can support some form of DM.

I'm not sure what the Reverend's sources are, but apparently the R300 only supports pre-sampled DM as well. Text

 

[beerbong]

didnt matrox invent displament mapping? coudl be wrong.

 

[Rand]

Originally posted by: beerbong
didnt matrox invent displament mapping? coudl be wrong.

I'm not sure, I know they invented EMBM and then licensed it to Microsoft.... the same may be true for DM but I can't say.
They certainly have the most comprehensive DM support of any grapohics card available right now though.

 

[Czar]

Originally posted by: Rand

Originally posted by: beerbong
didnt matrox invent displament mapping? coudl be wrong.

I'm not sure, I know they invented EMBM and then licensed it to Microsoft.... the same may be true for DM but I can't say.
They certainly have the most comprehensive DM support of any grapohics card available right now though.

not true, Matrox licensed EMBM from either Microsoft or Bitboys, it were the Bitboys who invented it and licensed it to Microsoft.

 

[Gstanfor]

Technical Brief: NVIDIA GeForce FX GPU

Refer to Page 7, Table 2.

The table is a GF4 /GF GX feature comparison.
Under the "Higher Order Surfaces" heading:
Higher Order Surface - supported
Continuous Tessellation - supported
Vertex Displacement Mapping - supported
Geometry Displacement Mapping - supported

Greg