In some circumstances, the renderer detects objects that need to have mapping coordinates applied.
If the renderer finds a parametric object that requires mapping, it automatically sets its Generate Mapping Coordinates toggle before rendering the scene. The toggle remains set after the rendering is done.
In the following cases, however, 3ds Max is unable to supply mapping coordinates automatically:
In these cases, 3ds Max is unable to render the scene completely. It displays a Missing Map Coordinates dialog that lists the objects the renderer couldn't map. To resolve the problem, apply a UVW Map modifier to the objects that the dialog lists.