Hi Marco,

> I happened in some cases the union of surfaces

Do you mean that you wanted to adjust the tolerance for one specific boolean union? Can you please send the 3DM file to me with the objects to be unioned inside of it so I can take a look at what is failing?



> Important would see different color surfaces with normal inverted priam applying the command "flip"

In the future I do want to add a display mode for showing back facing surfaces.

But what is the reason you were needing to use the Flip command in the first place?

- Michael