Michael tell me pleas why when I union this objects the edge where they connected not disappeared?
I noticed that some objects connects well without this border edge, but some has this edge. what is the principle?

Hi mir4ea - when 2 "analytic" planes are the things being unioned, it will form a larger plane and remove the interior edges. If you have objects that are not planar but just happened to be squished flat then that processing won't happen.

The other case where the edges can be removed is when the 2 trimmed surfaces being unioned have the exact same underlying surface, like if they were originally trimmed or booleaned out of the same surface.

- Michael

could you pleas explain more detail what do you mean by " are not planar but just happened to be squished flat"?

> could you pleas explain more detail what do you mean by " are not planar but just happened to be squished flat"?

Say for instance you have an "S" shaped flat path and then you sweep a line along it - the result will be a planar surface but it's a general surface made up of a bunch of control points, it's not the most simple "analytic plane" surface which is made up of only 4 corner control points. It's generally only those analytic planes that will get this special behavior in union, not other general surfaces with a whole bunch of control points in them that just happen to have all the control points in one plane.

So for instance if you want to have that behavior you want to build things by using Construct > Planar which builds a simple plane as the underlying surface, not use sweep or network for example to build the planar surfaces.

- Michael

Thank you.