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Andrew Lucas

Vertex Texture Fetch

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I'd need some help, as I'm trying to implement vertex texture fetching in my engine for faster rendering, but no matter what I do, it doesn't want to work. I have a Geforce 6 series graphics card, wich in theory should properly support it. I'm using Cg as my shader language, and I've used the compiler to check if I get any errors during compile, but everything worked out fine. I'm basically uploading my bone matrix data to a vertex texture I bind on initialization, and update it for each model I have to draw.
However, ingame, even the simplest models lag the scene horribly and they aren't drawn, like as if the vertex texture was full of zeroes. I'm pretty sure the maths in my vertex shader are working, and unless I actually bind the vertex texture in my code, it won't lag.

This is the code I use in the vertex shader:
bonemat[0] = tex2D(boneTexture, float2((vin.boneid*3)/512.0f, 0));
bonemat[1] = tex2D(boneTexture, float2(((vin.boneid*3)+1)/512.0f, 0));
bonemat[2] = tex2D(boneTexture, float2(((vin.boneid*3)+2)/512.0f, 0));

vertex[0] = vin.pos[0] * bonemat[0][0] + vin.pos[1] * bonemat[0][1] + vin.pos[2] * bonemat[0][2] + bonemat[0][3];
vertex[1] = vin.pos[0] * bonemat[1][0] + vin.pos[1] * bonemat[1][1] + vin.pos[2] * bonemat[1][2] + bonemat[1][3];
vertex[2] = vin.pos[0] * bonemat[2][0] + vin.pos[1] * bonemat[2][1] + vin.pos[2] * bonemat[2][2] + bonemat[2][3];
vertex[3] = 1;

normal[0] = vin.norm[0] * bonemat[0][0] + vin.norm[1] * bonemat[0][1] + vin.norm[2] * bonemat[0][2];
normal[1] = vin.norm[0] * bonemat[1][0] + vin.norm[1] * bonemat[1][1] + vin.norm[2] * bonemat[1][2];
normal[2] = vin.norm[0] * bonemat[2][0] + vin.norm[1] * bonemat[2][1] + vin.norm[2] * bonemat[2][2];

The bone ID is sent through the second multitexture unit as a float.

This is how I request the texture:
glBindTexture(GL_TEXTURE_2D, m_iBoneTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA_FLOAT32_ATI, 512, 2, 0, GL_RGBA, GL_FLOAT, 0);

And how I update this:
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 512, 2, GL_RGBA, GL_FLOAT, (*m_pbonetransform));

m_pbonetransform is a 128x3x4 float matrix. I tried getting over this for a long time, but I have no idea what I'm doing wrong here. I'd be really thankful for any help that there is.

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on an Nvidia card?

Secondly have you tried just a simple texture and single sample to see if you have it working?

Thirdly, a 6600 is ancient now. I specifically remember that it had problems with vertex texture fetches. Usually cripplingly bad performance or not working at all.


Also try using standard textures and not floats. Your hardware probably doesn't support floating point textures.

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