Boolean difference deforms solid

Rhino Rhino for Windows
1

I have a solid which was created by revolving a curve which is a join of many lines/arcs etc.
From this solid I’m attempting to subtract (boolean difference) a box which partially intersects with the solid.
After performing the operation the solid gets deformed at a location that is not even affected by the difference. The deformation only appears on the Perspective view (in render mode).

A video is attached for reference.


Thanks in advance!
2

try with DivideAlongCreases wth SplitAtTangents=yes after the boolean difference. I think is a meshing problem, not a geometry deformation.

3

Rhino has such meshing problems since many years (and versions). It usually happens with revolved surfaces such as pipes, car rims etc that are degree 1 in one direction and degree 2 or 3 in the other direction.

There is a simple “hack” which helps to solve the issue:

  1. Extract the desired surface (! _ExtractSrf).
  2. Run “Adjust closed surface seam” (! _SrfSeam) and use the “Quad” object snap to relocate the seam at 90 degrees from its original location. Alternatively, turn on the control points of the surface and use the “Point” object snap.
  3. Run “Adjust closed surface seam” again and move the seam back to where it was originally.

(Optional) In rare occasions that may add an extra row of control points along the original seam, so in this situation you may need to apply ! _RemoveKnot to remove the unnecessary row of control points.

4

Can you share a .3dm file with the geometry of the piece that has problems? You can use the vertical arrow above where you type your post, or drag the file into the are where you type your post.

As @DiegoKrause suggests it appears to be mesh problem since the problem only occurs in the render mode viewport. Rhino creates meshes for objects which are used for display in shaded, render, etc display modes. The default mesh settings are sometimes too coarse and cause problems. To refine the mesh settings Document Properties > Mesh.

Another possibility is a problem with the polycurve used to create the object.

1 Like
5

That kind of meshing issues happened for many years since Rhino 2 (especially Rhino 4). It’s related to the viewport coordinates mainly the revolved surfaces are affected. In many occasions it happens when a revolved object such like a car rim is being mirrored along the X or Y axis. It’s a bit confusing that either the original or the mirrored copy has such issues, but rarely both.

6

Hi - if you have an example of such behavior, please post that here.
-wim

7

Sure.

8

Hello - please post a file with the two input objects, before the Boolean operation.

-Pascal

9

Thanks a lot to all the responders.
I mnagaed to solve the issue using some kind of command involving mesh. It created a properly subtracted object and added a finer mesh.
I’m a complete noob at rhino so excuse if I make little sense or use the wrong terminology.