I have many brushes that are slightly shifted along one axis in a very small direction. When exporting these brushes to vmf, they are not accepted. As far as I know, in the hammer there is protection against this, and after saving the vmf map - re-entering it - the brushes automatically become planar. Is there any way to make polygons / brushes planar in wallworm / 3ds max? Thanks
So there are many tools available for this. Without seeing the scene in question, it's hard to be certain that the best tool is being used.
As a rule, most brushes should be built as CorVex (https://wallworm.com/store/corvex) or ShellVex (https://wallworm.com/store/shellvex) objects because they natively enforce several brush rules (like breaking non-planar polygons, turning non-convex quads into convex quads, enforcing all verts on grid, etc).
If not using CorVex and ShellVex, you can apply a Brushify (https://wallworm.com/store/brushify-modifier) modifier to a brush to enforce and fix many of the same things. (Brushify modifier requires Max 2016 SP2 or later).
All of these (and most other WW plugins are currently on sale through November 25 (https://wallworm.com/store/index.php?route=product/special)).
If not, you able to use the native brush tools, you can always use a Turn to Poly modifier and turn on Require Planar Polygons and Keep Polygons Convex to fix many situations. Generally speaking, it's best to always move brushes or brush sub-objects with appropriate snapping so that things generally stay on the grid--especially when not using the WW brush tools that will always keep things on the grid when using the Snap Precision options.