Microfacets Theory: A CDF for normal distribution given incident direction -
the paper microfacet models refraction through rough surfaces, page 3 section 3.1, describes ndf.
the problem: given incident ray v
i'd generate cdf f
given angle θ
gives probability normals distributed @ or less θ v
, i.e. dot(v,m)<=cos(θ)
w.p. f(θ)
.
for v = n
n
macrosurface normal simple (assuming isotropic ndf):
which easy compute common ggx or beckmann ndfs.
the paper gives formula harder integrate , still not useful.
any appreciated.
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