Because the sculpting tools in Mudbox are calibrated to an internal scale, an imported model has to be of the correct size. If the model were too small or too large, then the sculpting tools may not work predictably.
The model in the file ch04_01 is already of the correct size for sculpting in Mudbox, so you don’t need to scale it. However, when you import your own models, one way of checking whether the size of an imported figure is of the correct size is to compare it with the default human that ships with Mudbox. In other words, import your model and then insert Mudbox’s default human; if your model is about the same size as the default human, then it’s safe to proceed. If your model is not the same size, use the Scale tool to resize it. Another way to check for correct size is to use the scene XY grid. By default, each grid square is equivalent to half a meter (50 cm). So your figure should be about 1.5-2 m for the tools to work as expected.
If you are working in Mudbox 2009 or 2010, there is a known issue with scaling a model. When scaled, a model has to be exported at its new size and then reimported. Otherwise, the paint tools, specifically when painting bump maps, will not work properly.
