I have been trying to use the TXB shader assembly instruction so that I can bias the LOD of a texture from the shader but the instruction appears to act exactly like the TEX instruction. Is TXB supported by Radeon HD 3XXX and 4XXX cards?
The sample shader acts the same whether it is using TXB or TEX as the texture read instruction.
ATTRIB inColor = fragment.color.primary;
ATTRIB texcoord0 = fragment.texcoord;
MOV temp, texcoord0;
MOV temp.w, 10.0;
MOV temp.z, 0.0;
TXB texel, temp, texture, 2D;
MOV result.color, texel;