Dusty

Dust is deposited depending on the surface angle in world co-ordinates - +y being up. A horizontal surface gets the most dust, tapering off to none for a verfical surface, and none for inverted surfaces.

Dust color is faded into the surface color, the specular is reduced towards black (to get rid of those highlights), and the transparency and reflectivity are attenuated appropriately.

Noise is an option to give the dust more of a 'real' appearance....without it it looks more like grey paint.

You can get fairly good results with this shader, but it takes a lot of tweaking.

OPTIONS:

• Red, Green, and Blue
  New Option. Obviously, the colour of the dust...
• Dust thickness
  How heavy the dust is.
• Stickyness
  New Option. How strongly the dust sticks to the surface as the surface changes from horizonal to vertical.
• Noise
  toggle to turn noise on/off
• Noise Scaling
  the noise is computed using the Perlin noise function that is part of the standard mental ray library. Because the noise may not be in the correct scale with respect to your geometry, you can scale it.
• Noise Level
  how 'heavy' the noise influence on the dust is (a noise level of zero is the same as having noise turned off).
• Reflectivity Attenuation
  how much the reflectivity is attenuated at maximum dust.
• Transparency Attentuation
  how much the transparency is attenuated at maximum dust.

NOTE: I'm still not happy with this shader, but it's pretty useful to some so I've decided to release it. If you have any suggestions on how to make it more 'real', please pass them along.

Revision History:
January 10, 1995 - Initial Version