From 8a3e5b4d56b644808b4378a1f068486151a69ab2 Mon Sep 17 00:00:00 2001
From: phkahler <14852918+phkahler@users.noreply.github.com>
Date: Wed, 28 Oct 2020 14:17:48 -0400
Subject: [PATCH] Don't do numeric surface intersections if an exact curve has
 been copied. We don't want 2 overlapping but different sets of PWLs.

---
 src/srf/surfinter.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/srf/surfinter.cpp b/src/srf/surfinter.cpp
index 1e4fb396..0a827761 100644
--- a/src/srf/surfinter.cpp
+++ b/src/srf/surfinter.cpp
@@ -331,6 +331,7 @@ void SSurface::IntersectAgainst(SSurface *b, SShell *agnstA, SShell *agnstB,
                 sext = this;
                 shext = agnstA;
             }
+            bool foundExact = false;
             SCurve *sc;
             for(sc = shext->curve.First(); sc; sc = shext->curve.NextAfter(sc)) {
                 if(sc->source == SCurve::Source::INTERSECTION) continue;
@@ -341,8 +342,14 @@ void SSurface::IntersectAgainst(SSurface *b, SShell *agnstA, SShell *agnstB,
                 if(splane->ContainsPlaneCurve(sc)) {
                     SBezier bezier = sc->exact;
                     AddExactIntersectionCurve(&bezier, b, agnstA, agnstB, into);
+                    foundExact = true;
                 }
             }
+            // if we found at lest one of these we don't want to do the numerical
+            // intersection as well. Sometimes it will also find the same curve but
+            // with different PWLs and the polygon will fail to assemble.
+            if(foundExact)
+                return;
         }
 
         // Try intersecting the surfaces numerically, by a marching algorithm.