/usr/share/radiance/noise2.cal is in radiance-materials 4R0+20110410-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | frac(x)=x-floor(x);
hermite(p0,p1,r0,r1,t) = p0 * ((2*t-3)*t*t+1) +
p1 * (-2*t+3)*t*t +
r0 * (((t-2)*t+1)*t) +
r1 * ((t-1)*t*t);
rand2a(x,y) = 1-2*rand(.69692*x+.35084*y);
rand2b(x,y) = 1-2*rand(.05393*x+.96196*y);
rand2c(x,y) = 1-2*rand(.04234*x+.46180*y);
noise2(x,y) = noise_2( floor(x),frac(x),ceil(x),
floor(y),frac(y),ceil(y) );
noise_2(xl,xd,xu,yl,yd,yu) =
hermite(
hermite(rand2c(xl,yl),
rand2c(xu,yl),
rand2a(xl,yl),
rand2a(xu,yl),
xd),
hermite(rand2c(xl,yu),
rand2c(xu,yu),
rand2a(xl,yu),
rand2a(xu,yu),
xd),
(1-xd)*rand2b(xl,yl)+
xd*rand2b(xu,yl),
(1-xd)*rand2b(xl,yu)+
xd*rand2b(xu,yu),
yd);
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