C# Boolean difference between a surface and a solid

Rhino Developer
1

Hi,

Is it possible to obtain a Boolean difference between a surface and a solid, where the solid is the cutter (i.e. create a hole in a surface by a cylindrical solid passing through it)?

Thank you!

Cristina

2

Hi Christina,

If you create a surface and a solid, in Rhino, and use the BooleanDifference command, do you get the results you want?

– Dale

3

Hi Dale,

Unfortunately, if I choose the surface as the object to subtract from and the solid(the cylinder) the object to subtract with, then the result is a strange mix of the two (expected result is just a cutout in the surface).
For now I divided the code into step by step operations: splitting, selecting, deleting, but it would have been nice if it would work in one go, as when both objects are solids.
Thank you and any other idea is appreciated!

4

Running into the same issue. I don’t think the behavior shown (per the screenshots) is correct. I interpret boolean difference as a subtraction of one thing from another. I would have expected a hole…

5

how about splitting the surface using the cylinder and deleting the enclosed surface?

6

I had the same problem in code with rhinocommon.

I believe the normals of cylinder are flipped.
I remember @Dale showed a line of code that checks if closed brep orientation is inward, if yes I had to flip brep. Then the boolean difference

// The profile curve is a degree=1 curve. Thus, the extruded surface will
// have kinks. Because kinked surface can cause problems down stream, Rhino
// always splits kinked surfaces when adding Breps to the document. Since
// we are not adding this Brep to the document, lets split the kinked
// surfaces ourself.

brep.Faces.SplitKinkyFaces(RhinoMath.DefaultAngleTolerance, true);

// The profile curve, created by the input points, is oriented clockwise.
// Thus when the profile is extruded, the resulting surface will have its
// normals pointed inwards. So lets check the orientation and, if inwards,
// flip the face normals.

 if (BrepSolidOrientation.Inward == brep.SolidOrientation)
  brep.Flip();