Notation

Notation used in this site.

R - set of real number
RxR - Descates's product of R and R
RxRxR - Descartes's product of R and R and R

P- generally point in RxRxR, usually point at object.
N- normal at object's surface
index - index of refraction at P
index1 - also index of refraction at P
index2 - another index of refraction at P
index3 -and another index of refraction at P

Perlin's functions:
noise1: RxRxR -> R
noise3: RxRxR -> RxRxR
turbylency1: RxRxR -> R
turbylency3: RxRxR -> RxRxR
bias(g,t): RxR->R; pow( t, log( g ) / log( 0.5 ) )