Is wine reporting the right value for MaxVertexBlendMatrices ?

Julio Fernandez ucldb at
Sun Feb 10 04:27:22 CST 2008

Alex Jackson escribió:
>  > That said, GL_ARB_vertex_blend is not very common. Only MacOS 
> supports it, and
>  > it is software emulated there. The Linux ATI driver used to support 
> it until
>  > ATI switched to a different codebase. So this constant ends up beeing 0
>  > almost everywhere. The extension was dropped in favor of vertex 
> programs,
>  > since vertex programs appeared shortly after vertex blending and no 
> gl app
>  > was using it at this time. On Windows drivers emulate vertex blending 
> using
>  > vertex shaders.
>  >
>  > I am not sure if 0 is the correct value to return in case of no vertex
>  > blending support. What happens if you set it to 1? 1 would be a 
> reasonable
>  > default as well, because we're still able to transform vertices with one
>  > matrix(ie, unblened transformation). It could also be that this game 
> silently
>  > expects vertex blending to be supported: For one part, all dx8+ cards 
> support
>  > this feature on Windows, and on older cards Windows has software vertex
>  > processing which can perform blending in a slow, but working fashion.
>  >
>  > I have a patch for software emulated vertex blending somewhere, but I 
> dropped
>  > it because I didn't come across an app which uses this function. 
> Maybe its
>  > time to revive it, and continue the work on a fixed function replacement
>  > shader.
> Even on Windows, no OpenGL implementation that I know of supports 
> GL_ARB_vertex_blend other than ATI's (and as you've pointed out, the new 
> OpenGL stack that the Radeon HD's use on Windows and that all Radeons 
> now use on Linux has dropped it).
> History lesson:  Both GL_ARB_vertex_blend and D3D vertex blending are 
> historically tied to a specific piece of hardware: the original ATI 
> Radeon (GL_ARB_vertex_blend started out as GL_ATI_vertex_blend).  
> Presumably, due to ATI's historically spotty OpenGL driver performance 
> (okay, "historically" is being kind to ATI), any game developer who 
> wanted to use the Radeon's capabilities targeted their game for D3D 
> rather than OpenGL.   Consequently, when nVidia released the GeForce 3 
> (the first video card with vertex shaders) they did implement D3D vertex 
> blending via shaders in their D3D driver (since games were using it, and 
> it wouldn't do if the "new" GF3 couldn't handle effects that the "old" 
> Radeon could), but they didn't bother to implement it in their OpenGL 
> driver, even though ATI had gotten it ARB-approved some months before 
> the GF3 came out, since no games/apps were using it.  The other video 
> hardware makers (the few that were left by the DX8 era) followed NV's 
> example: implement D3D vertex blending via shaders or in software (for 
> entry-level and onboard hardware without vertex shaders), but don't 
> bother with GL_ARB_vertex_blend since no one uses it.
> The upshot is that GL_ARB_vertex_blend is an ARB extension In Name Only; 
> it's effectively ATI-only--and even ATI has abandoned it now.  On the 
> other hand, D3D vertex blending is universally available on modern and 
> semi-modern hardware regardless of maker, and it looks like even some 
> D3D9 games still use it instead of using vertex shaders.  So it's better 
> for WINE to implement vertex blending via vertex programs rather than 
> depending on GL_ARB_vertex_blend.
> --AWJ--
> ------------------------------------------------------------------------
> ------------------------------------------------------------------------
I am a bit lost now, but then, for a fast recap:

1- Theres some programs that call ConvertToIndexedBlendedMesh at 
2- wine returns (from opengl) MaxVertexBlendMatrices=0
3- d3d9x_30.dll misbehaves and generates vertex declarations with odd 
type codes and offsets when MaxVertexBlendMatrices=0
4- when we hack wine at IDirect3DDevice9Impl_GetDeviceCaps to return 4 
d3d9x_30.dll works properly and the programs run right

So my question is: is there any reason to not have wine return 
MaxVertexBlendMatrices=4 (as it works regardless of what opengl 
reports), and if so is it any other way for people willing to use some 
programs (like Everquest) to 'hack' it's value than modify 
IDirect3DDevice9Impl_GetDeviceCaps manually to make it return 4

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