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Re: ARB Vertex Program 1.0 Bug



Another list member spotted my mistake; Apple's implementation is indeed OK. The problem is that by applying the input mask, the code is not populating the q-coordinate of the texture (the homogenous divisor). This is a subtlety of OpenGL that I'd missed using fixed function but becomes very important with VPs!

This problem was the Ogre3D terrain demo, if anyone cares (well, OgreTerrainVertexProgram.cpp).

On Nov 14, 2004, at 09:26, Timothy Wayper wrote:
I think I've found a bug in Apple's implementation of ABPvp1.0, or at least the emulated version, but I'm not sure enough of the language myself to know for sure. It seems that a destination mask is not allowed when writing to result.texcoord (it does seem to be allowed when using result.postion). So this doesn't move the texture coords at all:

ATTRIB v24 = vertex.texcoord[0];
ATTRIB v25 = vertex.texcoord[1];
MOV result.texcoord[0].xy, v24;
MOV result.texcoord[1].xy, v25;

But this does:

ATTRIB v24 = vertex.texcoord[0];
ATTRIB v25 = vertex.texcoord[1];
MOV result.texcoord[0], v24;
MOV result.texcoord[1], v25;

The texture is only 2D in this case. No error is generated by glProgramStringARB, and the program other wise executes OK. This has got to be incorrect, right? Also, the Apple implementation does not accept a source swizzle on the MOVs above, but this does case an program string error. I'm testing this on 10.3.6.

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 >ARB Vertex Program 1.0 Bug (From: Timothy Wayper <email@hidden>)



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