logp - vs

Partial precision logp₂(x).

Syntax

logp dst, src

where

dst is the destination register.
src is a source register. Source register requires explicit use of replicate swizzle, that is, exactly one of the .x, .y, .z, .w swizzle components (or the .r, .g, .b, .a equivalents) must be specified.

Remarks

Vertex shader versions	1_1	2_0	2_x	2_sw	3_0	3_sw
logp	x	x	x	x	x	x

The following code fragment shows the operations performed.

float f = abs(src);
if (f != 0)
    dest.x = dest.y = dest.z = dest.w = (float)(log(f)/log(2));
else
    dest.x = dest.y = dest.z = dest.w = -FLT_MAX;

This instruction provides logarithm base 2 partial precision, up to 10 bits.