Greetings, I'm trying to implement a texture-palette using ATI_fragment_shader. I have a new FireGL card. For testing, I amd trying to apply a 256-entry look-up table to a GL_UNSIGNED_BYTE luminance 2D texture. All I get is a blank display, when I enable the shader. I'd appreaciate any suggestions. I've included my code below: GLuint nTex, nPalette; // dependent texture glGenTextures(1, &nTex); glActiveTextureARB( GL_TEXTURE0_ARB); glBindTexture( GL_TEXTURE_2D, nTex); unsigned char pSlice[256*256], *ptr; ptr = pSlice; for(int i=0; i<256; ++i) { memset(ptr, i, 256); ptr += 256; } glTexImage2D( GL_TEXTURE_2D, // target 0, // level 1, // internal format 256, // width 256, // height 0, // border GL_LUMINANCE, // format GL_UNSIGNED_BYTE, // type (void*) pSlice ); // texture palette glGenTextures(1, &nPalette); glActiveTextureARB( GL_TEXTURE1_ARB); glBindTexture( GL_TEXTURE_2D, nPalette ); float pfLUT[256*4], *pPtr; pPtr = pfLUT; for(int l=0; l<256; ++l) { pPtr[0] = l < 128 ? 0.0 : 1.0; pPtr[1] = pPtr[2] = pPtr[3] = 1.0; pPtr += 4; } glTexImage2D( GL_TEXTURE_2D, // target 0, // level 4, // internal format 256, // width 1, // height 0, // border GL_RGBA, // format GL_FLOAT, // type (void*) pfLUT ); simpleFragmentShader = glGenFragmentShadersATI(1); glBindFragmentShaderATI (simpleFragmentShader); glBeginFragmentShaderATI(); glSampleMapATI ( GL_REG_0_ATI, GL_TEXTURE0_ARB, GL_SWIZZLE_STR_ATI); glPassTexCoordATI(GL_REG_0_ATI, GL_REG_0_ATI, GL_SWIZZLE_STR_ATI); // dummy operation to end the first pass (better way ?) glColorFragmentOp1ATI (GL_MOV_ATI, GL_REG_2_ATI, GL_NONE, GL_NONE, GL_REG_3_ATI, GL_NONE, GL_NONE); // Dependent texture read glSampleMapATI ( GL_REG_1_ATI, GL_REG_0_ATI, GL_SWIZZLE_STR_ATI); glColorFragmentOp1ATI (GL_MOV_ATI, GL_REG_0_ATI, GL_NONE, GL_NONE, GL_REG_1_ATI, GL_NONE, GL_NONE); glEndFragmentShaderATI();

Don't call glSampleMap and glPassTexCoord with the same destination register. Chances are the shader compiler will suppose you're performing two passes at this time, thus three passes til the end of the shader, and then will fail to compile.