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 these problems with two separate effects. First, Edge can roughen or blur an object's profile edge; second, Edge can roughen the edges of shadows falling onto the object.


Procedure

To modify the profile edge of an object:

In the Material dialogue box, set the object's transparency to 1.

Select Edge as the material shader.

Edit Edge's profile parameters.

To modify the edges of shadows falling onto the object.

In the Material dialogue box, select Edge as the material shader.

Edit Edge's shadow parameters.


Parameters

Profile Edges

Edge works 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 effects the edge, and how the surface color effects 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.

Profile Overall

Relative to controls whether the edge effects are relative to the World Center or the Object Center.

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.

Profile Noise Effect

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.

Scale controls the size of the largest clumps of noise.

Roughness controls how noisy the edge of the noise is.

Profile Color Effect

Similar to Landscape's Image Effect , the Color Effect uses the aggregate color information of the object's diffuse textures to generate the edge.

Influence again sets the relative influence of the effect; see above.

Shadow Edges

To roughen the edges of shadows, Edge employs a trick very similar to displacement mapping: it momentarily raises the surface above the geometry, so that shadows falling on the surface reflect the shape of the displacement, not the underlying geometry.

The artist controls how far the surface is displaced, what kind of noise effects the displacement, and how the surface color effects the displacement.

Shadow Overall

Relative to controls whether the edge effects are relative to the World Center or the Object Center.

Amount controls how much the surface is temporarily displaced (measured in SoftImage units), and thereby how rough the edge of the shadow will appear to be. Larger values cause deeper cuts into the shadow, while smaller values cause less of an effect. A value of 0 essentially disables the entire effect.

Shadow Noise Effect

Influence sets the relative influence that the Noise Effect will have on the shadow's 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.

Scale controls the size of the largest clumps of noise.

Roughness controls how noisy the edge of the noise is.

Shadow Color Effect

Again, the Color Effect uses the aggregate color information of the object's diffuse textures to generate the shadow's edge.

Influence again sets the relative influence of the effect; see above.