texldb (Pixel Shader)

Projected texture load instruction. This instruction uses the fourth element (.a or .w) to bias the texture-sampling level of detail (LOD) just before sampling.

Syntax

where

• [_pp] is optional partial precision. See Partial Precision.
• dst is the destination register.
• src0 is a source register.
• src1 is a source register.

For the restrictions when using texldb, see the texld instruction.

Remarks

texldb biases the mipmap LOD, computed normally as part of the sample process by the (signed) value in src0.w. Recall that positive bias values will result in smaller mipmaps being selected and vice versa. For ps_2_0 and ps_s_x, bias values can be within the range [-3.0,+3.0]. For ps_3_0, bias values can be within the range [-16.0,+15.0]. Bias values outside this range will produce undefined results. The sampler state D3DSAMP_MIPMAPLODBIAS is still honored, and the texldb bias is added to this, but on a per-pixel basis. After the biased LOD is computed, D3DSAMP_MAXMIPLEVEL is still honored and the texture sample occurs. After texldb, the contents of src0 are unaffected (unless dst is the same register).

Instruction Information