luminance VEX function

Compute the luminance of the RGB color specified by the parameters

Contexts: image3d, chop, cop, pop, sop, surface, displace, fog, light, shadow, photon, cvex

  1. float luminance(vector )

  2. float luminance(vector4 )

  3. float luminance(float r, float g, float b)

Compute the luminance of the RGB color specified by the parameters