To change the bounding box scale

1. In the Memory and Performance Options section of the Render Settings window, turn on Use Displacement Bounding Box (it is on by default).
2. Estimate how much the surface will grow when it is displacement-mapped. Consider the following:
   • If the bounding box of the displaced surface will be more than 50 percent larger than the bounding box for the original surface in World Space, open the surface’s Attribute Editor and enlarge the bounding box scale.
   • If the bounding box of the displaced surface will be less than 50 percent larger than the bounding box for the original surface in World Space, open the surface’s Attribute Editor and reduce the bounding box scale to optimize the rendering speed and memory.
   • If you choose to let Maya automatically compute the proper bounding box scale for the displaced object, click Calculate Bounding Box Scale in the Attribute Editor and Maya automatically sets the bounding box scale for the surface.
3. Render.

   If the estimated bounding box scale is too small, a warning message appears in the render log with instructions on how to set the bounding box scale correctly. An example message:

   Warning: The bounding box is too small for shape “nurbsSphereShape1”. Reset the bounding box scale to: 1.56778 1.56778 1.56778. You can use the following mel commands: setAttr nurbsSphereShape1.boundingBoxScale -type double3 1.56778 1.56778 1.56778;

4. Adjust the bounding box scale as recommended in the render log message.
5. Render again.