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(c) Compute the fast Fourier transform of the resultant array. Does it appear to be
a blue-noise distribution?
(d) Try this process again with various values for r . Below what frequency (in
terms of r ) is there relatively little energy?
(e) Now generate a similar occupancy array using stratified sampling, and com-
pare the frequency spectra of the two processes. Describe any differences you find.
(f) Generalize to 2D.
(g) Implement Mitchell's [Mit87] point diffusion algorithm for generating blue
noise, and compare its results to the others.
Exercise 32.12: For a rectangular area light, write code to sample a point from
the light uniformly with respect to area. Do the same for a spherical source. For
the sphere, recall that the projection ( x , y , z )
r ) , where r = x 2 + z 2
is an area-preserving map from the unit-radius cylinder about the y -axis, extending
from y =
( x
/
r , y , z
/
1to y = 1, onto the unit sphere.
 
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