NFC, Performance: Use OpenMP for boolean function MakeItersectionCurvesAgainst.

This is the last long-running single-threaded part of the boolean code. On one test model this took Regenerate form 27 seconds down to 18s. The critical sections needed a name (into) because that object must not be modified while in use in different places.

src/srf/boolean.cpp

@@ -640,8 +640,10 @@ void SShell::CopySurfacesTrimAgainst(SShell *sha, SShell *shb, SShell *into, SSu
 }
 
 void SShell::MakeIntersectionCurvesAgainst(SShell *agnst, SShell *into) {
-    SSurface *sa;
-    for(sa = surface.First(); sa; sa = surface.NextAfter(sa)) {
+#pragma omp parallel for
+    for(int i = 0; i< surface.n; i++) {
+        SSurface *sa = &surface[i];
+
         SSurface *sb;
         for(sb = agnst->surface.First(); sb; sb = agnst->surface.NextAfter(sb)){
             // Intersect every surface from our shell against every surface

src/srf/surfinter.cpp

@@ -27,6 +27,8 @@ void SSurface::AddExactIntersectionCurve(SBezier *sb, SSurface *srfB,
     SBezier sbrev = *sb;
     sbrev.Reverse();
     bool backwards = false;
+#pragma omp critical(into)
+    {
         for(se = into->curve.First(); se; se = into->curve.NextAfter(se)) {
             if(se->isExact) {
                 if(sb->Equals(&(se->exact))) {
@@ -40,6 +42,7 @@ void SSurface::AddExactIntersectionCurve(SBezier *sb, SSurface *srfB,
                 }
             }
         }
+    }// end omp critical
     if(existing) {
         SCurvePt *v;
         for(v = existing->pts.First(); v; v = existing->pts.NextAfter(v)) {
@@ -101,8 +104,11 @@ void SSurface::AddExactIntersectionCurve(SBezier *sb, SSurface *srfB,
              "Unexpected zero-length edge");
 
     split.source = SCurve::Source::INTERSECTION;
+#pragma omp critical(into)
+    {
         into->curve.AddAndAssignId(&split);
     }
+}
 
 void SSurface::IntersectAgainst(SSurface *b, SShell *agnstA, SShell *agnstB,
                                 SShell *into)
@@ -456,8 +462,11 @@ void SSurface::IntersectAgainst(SSurface *b, SShell *agnstA, SShell *agnstB,
             // And now we split and insert the curve
             SCurve split = sc.MakeCopySplitAgainst(agnstA, agnstB, this, b);
             sc.Clear();
+#pragma omp critical(into)
+            {
                 into->curve.AddAndAssignId(&split);
             }
+        }
         spl.Clear();
     }
 }