Example Trim surface

Rhino Developer
#1

Hi, has anyone an example command for RhinoCommon that trims a surface with another surface? I searched in the wiki and the github repo but did not find anything.

Thanks a lot

#2

Unless you are working with a closed cutter, you are probably better of using Split, and then decide which parts to keep, based on size, location, etc.

http://4.rhino3d.com/5/rhinocommon/html/M_Rhino_Geometry_Brep_Split.htm
http://4.rhino3d.com/5/rhinocommon/html/M_Rhino_Geometry_Brep_Split_1.htm

http://4.rhino3d.com/5/rhinocommon/html/M_Rhino_Geometry_Brep_Trim.htm

#3

I tried using split but I got an empty array out of the call. My code is:

 var brepList = new List<Brep>();
 foreach (var obj in ObjectToTrim)
 {
   var brepToTrim = obj.Brep();
   if (brepToTrim == null)
   {
     continue;
   }

   var selectionPoint = obj.SelectionPoint();
   var splittedBreps = brepToTrim.Split(CuttingObject, Tolerance);
   foreach (var brep in splittedBreps)
   {
     if (!brep.IsPointInside(selectionPoint, Tolerance, true))
     {
       brepList.Add(brep);
     }
   }
 }
 return brepList.ToArray();

and at the end, even if the two breps are clearly intersecting, I got an empty list.

#4

I think your method of selecting the remaining parts not correct. Because Brep.IsPointInside only makes sense if the Brep is closed.
Why not perform a distance test with Brep.ClosestPoint. If the distance is larger than the tolerance, that part should be disregarded.

#5

I updated it using ClosestPoint but still, using the debugger to step through the code gives me splittedBreps.Count == 0 for every surface I select. In this context:

  • ObjectToTrim is a list of ObjRef
  • CuttingObject is an array of Brep
  • Tolerance is the absolute tolerance taken from RhinoApp

I really cannot understand what I am doing wrong.

#6

Here is a simple sample that you an reference.

https://github.com/dalefugier/SampleCsCommands/blob/master/SampleCsTrimSurface.cs

#7

Thanks a lot! That really helped!