logp - vs

Partial precision logp₂(x).


logp dst, src



  • 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.


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));
    dest.x = dest.y = dest.z = dest.w = -FLT_MAX;   

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

Vertex Shader Instructions