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Edge
Bump mapping is a powerful tool for suggesting geometric detail when such
detail would be impractical as actual geometry. Unfortunately, two situations
in particular cause a bump mapped surface to look fake: when the profile edge
of the surface looks too smooth, and when shadows falling on the surface look
too smooth.
The Edge shader remedies the first of these problems.
Edge can roughen or blur
an object's profile edge. The EdgeShadow shader
remedies the second. It can roughen the edges of shadows falling onto the object.
Parameters
Profile Edges
Edge and EdgeShadow work by making the
object transparent at its profile edges. The artist controls how much of the edge should become
transparent, how blurry the edge should be, what kind of noise affects the
edge, and how the surface color affects the edge.
NOTE: Edge only works on "profile" edges, that is,
edges that curve away from the camera. Edge applied
to a cube would have no effect. Also note that it does not work on
concave objects.
Profile Overall
Amount controls how much of the edge is made transparent, and thereby
how rough the edge will appear to be. Larger values cause deeper cuts into the
profile, while smaller values cause less of an effect. A value of 0 essentially
disables the entire effect.
Blur controls how fuzzy this edge is. A value of 0 gives a sharp edge
line, while a value of 1 will cause the entire edge region to be blurred.
Relative to World and Relative to Object controls whether the edge
effects are relative to the world coordinate system or the object coordinate system.
Profile Noise Effect
Noise Influence controls whether the irregular edge profile is influenced by noise.
Influence sets the relative influence that the Noise Effect will have on
the profile edge, as compared to the Color effect - similar to the way Landscape's influence function works. When specifying
Influences, the ratio of the influences is all that is important.
Roughness controls how noisy the edge of the noise is.
Scale controls the size of the largest clumps of noise.
Profile Color Effect
Diffuse Influence controls whether the irregular edge profile is influenced by the diffuse
color.
Influence again sets the relative influence of the effect; see above.
Similar to Landscape's Image Effect , the
Color Effect uses the object's diffuse color to generate the edge.
Diffuse is the same color used by the illumination shader.
Shadow Edges
To roughen the edges of shadows, EdgeShadow employs the same
algorithm and parameters as Edge.
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