You have to specify both the minimum depth and the maximum depth. This is to steer the recursive subdivision of the octree. If the mimimum depth is set to 2, it means that voxels in the octree at level 0 and 1 will always be subdivided, regardless of their contents.
The maximum depth gives the upper bound for the octree subdivision. If mindepth and maxdepth are equal, the octree will be a uniform voxelspace (a 3D array of cells). For instance, with both mindepth and maxdepth set to 10, you will get 2^10 * 2^10 * 2^10 = 2^30 = 1 giga voxels. As each voxel may lead to 0,1 or 2 polygons, you will potentially end up with 2000 million polygons. This will probably tell you that these depth values are to be kept low. Usefull ranges are 2-7.
The minumum depth should be lower or equal to maxdepth. Using a lower value for mindepth will give you a faster polygonization. Also, larger polygons will remain non-subdivided when possible.
Polygonize
When you press the 'Polygonize' button, you must specify an output
file. This file is in an intermediate format and can be converted
to either VRML or Inventor in the Channels submenu if you wish.
When you have selected the output file, the model will be facetted.
This may take some time, when finished your current model will have
been replaced by its facetted version, stripped from all information
other then geometry. Although when you export your model to VRML/Inventor,
the surface attributes will be preserved.
