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| Class | Reflectance | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Synopsis |
Approximation of surface with many small areas of concentric rings of scratches or ridges repeated over the surface. Such surfaces reflect light differently in different directions (the technical term for this is 'anisotropic reflection').
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| Arguments |
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| Location | lishpro | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Description |
Anisotropic reflectance shader which simulates the
directional reflectance properties of surfaces
covered in a repeating pattern of concentric
scratches or grooves.
Surface scratches are approximated by thin cylinders. The degree of anisotropy of the surface can be controlled by varying the distance between the cylinders using the "cylinder distance" parameter. A distance of 0.0 gives isotropic (normal) reflection, and distance of 2.0 gives maximum anisotropy. A distance of greater than 2.0 gives a flat floor between cylinders which reflects light isotropically. The height of the floor across the cylinders may also be specified with the "floor height" parameter. A value of 0.0 gives no floor, a value of 1.0 gives a completely flat, isotropic surface. The centre of the circular pattern is defined to be at (0.5, 0.5) in texture space. The horizontal and vertical frequency of the pattern may be controlled using the "width" and "height" parameters. Setting either of these to 1.0 (the default) prevents the pattern from repeating. The pattern is also aligned with the s and t texture coordinate axes and hence texture coordinates or a texture space must be supplied to ensure the correct results. Texture coordinates may also be used to control the frequency, orientation and alignment of the circular patches. If texture coordinates are used then the primitive must also be constructed entirely of triangles, use LiPrimitiveTriangulate if this is not the case. If the texture coordinates are supplied by a texture space shader then primitive need not be triangulated, but the behaviour of the shader along surfaces with constant s or t is undefined. The "overlap area" argument controls whether the circles overlap or not. A value of 0.0 means the circles are placed side by side, while 1.0 makes large parts of the circles overlapped by other circles. For example, the surface effect created by a brushing machine, which gives an overlap, can be created with setting "overlap area" to value close to 0.3. The "scratches" argument specifies whether circles representing scratches on a surface should appear. 0.0 means that there are no scratches while 1.0 means that the scratches are clearly visible. The "scratches thickness" argument controls thickness of scratches. The smaller value is set the thinner scratches are created. "scratches variation" controls whether the scratches are uniform (0.0) or there is colour variation along lines (1.0 gives the strongest variation). "scratches variation scale" specifies how rapid colour variation is. Small values create a grain looking pattern. High values give a smooth transition between colours. Reflectance co-efficients are provided as arguments which allow specification of the amount of ambient light ( "ambient factor"), diffuse light ( "diffuse factor") and specular light ( "specular factor") components as for the plastic shader. The sharpness of the specular highlights can be controlled using the "roughness" parameter and the colour may be controlled using the "specular colour" parameter.
Finally, the overall scale of the pattern produced is controlled by the parameter "scale", allowing you to accurately account for changes to the scale at which you model your geometry.
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