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Surface Normal
Normal Vector
(Term of geometry/computer graphics)
An vector perpendicular to a surface.
At the same time, the direction of this vector
determines the orientation of the surface.
In the case of polygons, this direction is
usually determined by the right hand rule.
In computer graphics, manipulations of the normal
vector are often used as a way to simulate
geometrical detail on otherwise planar surfaces.
In this case, a function will determine small aberrations
of the true direction of the normal vector on every
point of the surface, in order special
create highlight or shadow effects. If eg. the vector
is slightly shifted in accordance to a sinus function,
then the surface will appear in a rendered image,
as if it were made of corrugated material (except for
the edges).
In the Radiance software, texture modifiers are
used for this purpose.
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