FreeCAD Programmatically Bisect Two Back-to-Back Symmetrical Triangles Into Four Right Triangles

FreeCAD Programmatically Bisect Two Back-to-Back Symmetrical Triangles Into Four Right Triangles.md

FreeCAD Programmatically Bisect Two Back-to-Back Symmetrical Triangles Into Four Right Triangles

I am a fucking noob. I don't know how to do this properly, so I created a programmatic way to do this for-realium :3 :3 :3

main.py

import math, traceback, Part
from collections import namedtuple
Point = namedtuple("Point", "x y z")
def line_intersect_2d(p1, p2, p3, p4):
    x1, y1, x2, y2, x3, y3, x4, y4 = p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y
    a, b, c, d, e, f = (x1*y2 - y1*x2), (x3 - x4), (y3 - y4), (x1 - x2), (y1 - y2), (x3*y4 - y3*x4)
    denom = d*c-e*b
    if abs(denom) < 1e-9:
        raise ValueError("Lines are parallel")
    return FreeCAD.Vector((a*b-d*f)/denom, (a*c-e*f)/denom, p1.z)

def centroid(pts):
    n = len(pts)
    return FreeCAD.Vector(
        sum(p.x for p in pts)/n,
        sum(p.y for p in pts)/n,
        sum(p.z for p in pts)/n,
    )

def make_polygons(ls_ls):
    return [Part.Face(Part.makePolygon(ls)) for ls in ls_ls]

def _main(original_shape_name, new_shape_name, tol):
    sel = Gui.Selection.getSelectionEx()
    orig_faces = FreeCAD.ActiveDocument.getObject(original_shape_name).Shape.Faces
    face_count = sum(1 for s in sel for name in s.SubElementNames if name.startswith("Face"))
    assert face_count == 2, f"Expected exactly 2 faces, got {face_count} — reselect!"
    pts = set()
    for s in sel:
        for name, sub in zip(s.SubElementNames, s.SubObjects, strict=True):
            if name.startswith("Face"):
                for v in sub.Vertexes:
                    pts.add(Point(x=v.X, y=v.Y, z=v.Z))
    assert len(pts) == 4, f"Expected exactly 4 unique points, got {len(pts)} — check for a shared-edge mismatch or duplicate geometry!"
    cx, cy = (sum(p.x for p in pts) / 4), (sum(p.y for p in pts) / 4)
    p0, p1, p2, p3 = sorted(pts, key=lambda p: math.atan2(p.y - cy, p.x - cx))
    I = line_intersect_2d(p0, p2, p1, p3)
    f1, f2, f3, f4 = make_polygons(([p0, p1, I, p0], [p1, p2, I, p1], [p2, p3, I, p2], [p3, p0, I, p3]))
    c1, c2 = centroid([p0, p2, p1]), centroid([p1, p3, p0])
    kept_faces = []
    for f in orig_faces:
        fc = centroid([FreeCAD.Vector(v.X, v.Y, v.Z) for v in f.Vertexes])
        if fc.distanceToPoint(c1) < tol or fc.distanceToPoint(c2) < tol:
            continue
        kept_faces.append(f)
    face_difference = (len(orig_faces) - len(kept_faces))
    assert face_difference == 2, f"Expected exactly difference of unique points, got {face_difference} — Change `tol` parameter!"
    Part.show(Part.makeCompound([*kept_faces, f1, f2, f3, f4]), new_shape_name)

def main(original_shape_name, new_shape_name, tol):
    try:
        _main(original_shape_name=original_shape_name, new_shape_name=new_shape_name, tol=tol)
    except BaseException:
        traceback.print_exc()

main(original_shape_name="CKB_119t_002", new_shape_name="CKB_119t_", tol=0.7)
print()

min.py

import math,traceback as B,Part as H
from collections import namedtuple as C
U,E,A=C('Point','x y z'),len,sum
def V(g,h,i,j):
	B,C,D,E,F,G,H,I=g.x,g.y,h.x,h.y,i.x,i.y,j.x,j.y;J,K,L,M,N,O=B*E-C*D,F-H,G-I,B-D,C-E,F*I-G*H;A=M*L-N*K
	if abs(A)<1e-09:raise ValueError('Lines are parallel')
	return FreeCAD.Vector((J*K-M*O)/A,(J*L-N*O)/A,g.z)

def J(a):B=E(a);return FreeCAD.Vector(A(A.x for A in a)/B,A(A.y for A in a)/B,A(A.z for A in a)/B)

def W(a):return[H.Face(H.makePolygon(A))for A in a]

def D(a,b,c):
	T='Face';M=Gui.Selection.getSelectionEx();N=FreeCAD.ActiveDocument.getObject(a).Shape.Faces;O=A(1 for A in M for B in A.SubElementNames if B.startswith(T));assert O==2,f"Expected exactly 2 faces, got {O} — reselect!";B=set()
	for P in M:
		for(X,Y)in zip(P.SubElementNames,P.SubObjects,strict=True):
			if X.startswith(T):
				for K in Y.Vertexes:B.add(U(x=K.X,y=K.Y,z=K.Z))
	assert E(B)==4,f"Expected exactly 4 unique points, got {E(B)} — check for a shared-edge mismatch or duplicate geometry!";Z,d=A(A.x for A in B)/4,A(A.y for A in B)/4;C,D,F,G=sorted(B,key=lambda p:math.atan2(p.y-d,p.x-Z));I=V(C,F,D,G);e,f,g,h=W(([C,D,I,C],[D,F,I,D],[F,G,I,F],[G,C,I,G]));i,j=J([C,F,D]),J([D,G,C]);L=[]
	for Q in N:
		R=J([FreeCAD.Vector(A.X,A.Y,A.Z)for A in Q.Vertexes])
		if R.distanceToPoint(i)<c or R.distanceToPoint(j)<c:continue
		L.append(Q)
	S=E(N)-E(L);assert S==2,f"Expected exactly difference of unique points, got {S} — Change `tol` parameter!";H.show(H.makeCompound([*L,e,f,g,h]),b)

def main(original,new,tol):
	try:D(original,new,tol)
	except BaseException:B.print_exc()

main(original='CKB_119t_003',new='CKB_119t_',tol=.7)
print()