Microsoft KB Archive/153507

= Microsoft Knowledge Base =

How to Use Displacement Maps with Patch Objects
Last reviewed: July 11, 1996

Article ID: Q153507

The information in this article applies to:


 * Softimage 3D for IRIX, version 3.5

SUMMARY
Here is some useful information on using displacement maps with patch objects.

When aiming to create a great displacement map texture, consider the following questions.


 * How much subdivision is required on a patch geometry to get excellent close up detail when using a displacement map?
 * Is a gray-tone alpha channel better than a black and white one? Which gives better results?

MORE INFORMATION
For precisely defined detail, one basic rule to remember is that the finer you want the detail on the displacement map image to be the higher the step value should be.

For example, if the grid in an image contains cells of 10x10 units, the step in the grid has to be high (4 or 5) to get high definition.

Here is a good way to see if the resolution of your grid is high enough. In Info->Selection, set the Curve values the same as the Step values.

This gives you a good indication of the amount of geometry that can be displaced. If the detail in the texture map is finer than the size of the visible squares, the displacement will obviously be an average of the two.

Concerning the alpha channel, use mid-gray for level surface, full white for bumps, and full black for holes.

NOTE: You have to look at a lot of previews to see if any models touching the surface are colliding, which they should not be. Also, the roughness values in mental ray should be quite low compared to standard Softimage roughness values (0.1 - 0.3).