Hi,
I’m back trying to construct a water-tight thread brep in GHPython from scratch and failing.
Some of you might remember this topic from about two years ago, where I encountered the same issue, while trying something similar, and never really managed to solve it.
I’m trying a different way of constructing the thread here, namely by lofting its defining helical curves.
This Grasshopper definition leads to a closed thread brep, which is fabulous.
However, when translated to GHPython using RhinoCommon a broken, open brep is the result.
import Rhino.Geometry as rg
import scriptcontext as sc
MTOL = sc.doc.ModelAbsoluteTolerance
ATOL = sc.doc.ModelAngleToleranceRadians
# Hardcoded Constants Matching Input Geometry (don't change)
PLANE = rg.Plane.WorldYZ
MAJOR_DIAMETER = 4.0 # M4
PITCH = 0.7 # M4
TURN_COUNT = 123
if __name__ == "__main__":
# Create Thread
thread_brep = rg.Brep.CreateFromLoft(C, rg.Point3d.Unset, rg.Point3d.Unset, rg.LoftType.Straight, False)[0]
# Trim Thread to Length And Construct Caps
start_plane = rg.Plane(PLANE.Origin + PLANE.ZAxis * (PITCH + MTOL), -PLANE.XAxis, PLANE.YAxis)
end_plane = rg.Plane(PLANE.Origin + PLANE.ZAxis * (PITCH * TURN_COUNT - MTOL), PLANE.XAxis, PLANE.YAxis)
cutter_domain = rg.Interval(-MAJOR_DIAMETER, MAJOR_DIAMETER)
cutter_breps = []
cap_breps = []
for plane in [start_plane, end_plane]:
# End cutters
rect = rg.Rectangle3d(plane, cutter_domain, cutter_domain)
corners = [rect.Corner(i) for i in range(4)]
p, q, r, s = corners
cutter_breps.append(rg.Brep.CreateFromCornerPoints(p, q, r, s, MTOL))
# End caps
rc, crvs, _ = rg.Intersect.Intersection.BrepPlane(thread_brep, plane, MTOL)
boundary_breps = rg.Brep.CreatePlanarBreps(crvs, MTOL)
cap_breps.append(boundary_breps[0])
thread_brep_segments = thread_brep.Split(cutter_breps, MTOL)
thread_brep = None
for brep_seg in thread_brep_segments:
#brep_seg.Edges.RemoveNakedMicroEdges(MTOL)
#brep_seg.Edges.MergeAllEdges(ATOL)
bbox = brep_seg.GetBoundingBox(False)
dist_start = start_plane.DistanceTo(bbox.Center)
dist_end = end_plane.DistanceTo(bbox.Center)
if(abs(dist_start - dist_end) < MTOL):
thread_brep = brep_seg
break
#faces = [f.DuplicateFace(False) for f in thread_brep.Faces]
#thread_brep = rg.Brep.JoinBreps(faces, MTOL)[0]
start_cap, end_cap = cap_breps
thread_brep.Join(start_cap, MTOL, False)
thread_brep.Join(end_cap, MTOL, True)
# Outputs
B = thread_brep
Superficially, I do exactly the same, however I suspect the Grasshopper components to do some cleaning up and/or rebuilding here and there, basically some magic behind the scenes.
I’ve tried some de- and reconstructing the brep, but to no avail. Cleaning up naked micro edges and merging all edges also didn’t seem to do much.
Thanks for taking a look! 
thread-rhf.gh (127.2 KB)