Use poly2tri for triangulation. This fixes some cases where polyPartition couldn't triangulate successfully. Reported as issue #9 in polyPartition repository. Tested with MotorHalter_0.stl cut at 1.2

xs/src/poly2tri/common/utils.h

@@ -0,0 +1,122 @@
+/*
+ * Poly2Tri Copyright (c) 2009-2010, Poly2Tri Contributors
+ * http://code.google.com/p/poly2tri/
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * * Neither the name of Poly2Tri nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without specific
+ *   prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef UTILS_H
+#define UTILS_H
+
+// Otherwise #defines like M_PI are undeclared under Visual Studio
+#define _USE_MATH_DEFINES
+
+#include <exception>
+#include <math.h>
+
+namespace p2t {
+
+const double PI_3div4 = 3 * M_PI / 4;
+const double PI_div2 = 1.57079632679489661923;
+const double EPSILON = 1e-12;
+
+enum Orientation { CW, CCW, COLLINEAR };
+
+/**
+ * Forumla to calculate signed area<br>
+ * Positive if CCW<br>
+ * Negative if CW<br>
+ * 0 if collinear<br>
+ * <pre>
+ * A[P1,P2,P3]  =  (x1*y2 - y1*x2) + (x2*y3 - y2*x3) + (x3*y1 - y3*x1)
+ *              =  (x1-x3)*(y2-y3) - (y1-y3)*(x2-x3)
+ * </pre>
+ */
+Orientation Orient2d(const Point& pa, const Point& pb, const Point& pc)
+{
+  double detleft = (pa.x - pc.x) * (pb.y - pc.y);
+  double detright = (pa.y - pc.y) * (pb.x - pc.x);
+  double val = detleft - detright;
+  if (val > -EPSILON && val < EPSILON) {
+    return COLLINEAR;
+  } else if (val > 0) {
+    return CCW;
+  }
+  return CW;
+}
+
+/*
+bool InScanArea(Point& pa, Point& pb, Point& pc, Point& pd)
+{
+  double pdx = pd.x;
+  double pdy = pd.y;
+  double adx = pa.x - pdx;
+  double ady = pa.y - pdy;
+  double bdx = pb.x - pdx;
+  double bdy = pb.y - pdy;
+
+  double adxbdy = adx * bdy;
+  double bdxady = bdx * ady;
+  double oabd = adxbdy - bdxady;
+
+  if (oabd <= EPSILON) {
+    return false;
+  }
+
+  double cdx = pc.x - pdx;
+  double cdy = pc.y - pdy;
+
+  double cdxady = cdx * ady;
+  double adxcdy = adx * cdy;
+  double ocad = cdxady - adxcdy;
+
+  if (ocad <= EPSILON) {
+    return false;
+  }
+
+  return true;
+}
+
+*/
+
+bool InScanArea(const Point& pa, const Point& pb, const Point& pc, const Point& pd)
+{
+  double oadb = (pa.x - pb.x)*(pd.y - pb.y) - (pd.x - pb.x)*(pa.y - pb.y);
+  if (oadb >= -EPSILON) {
+    return false;
+  }
+
+  double oadc = (pa.x - pc.x)*(pd.y - pc.y) - (pd.x - pc.x)*(pa.y - pc.y);
+  if (oadc <= EPSILON) {
+    return false;
+  }
+  return true;
+}
+
+}
+
+#endif