triangulate fans locally.

solvespace · Jul 18, 2020 · 316b8c3 · 316b8c3
1 parent 188b2e2
commit 316b8c3
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Showing 2 changed files with 69 additions and 6 deletions.
diff --git a/src/polygon.h b/src/polygon.h
@@ -131,7 +131,7 @@ class SContour {
     void FindPointWithMinX();
     Vector AnyEdgeMidpoint() const;
 
-    bool IsEar(int bp, double scaledEps) const;
+    bool IsEar(int ap, int bp, int cp, double scaledEps) const;
     bool BridgeToContour(SContour *sc, SEdgeList *el, List<Vector> *vl);
     void ClipEarInto(SMesh *m, int bp, double scaledEps);
     void UvTriangulateInto(SMesh *m, SSurface *srf);

diff --git a/src/srf/triangulate.cpp b/src/srf/triangulate.cpp
@@ -213,9 +213,7 @@ bool SContour::BridgeToContour(SContour *sc,
     return true;
 }
 
-bool SContour::IsEar(int bp, double scaledEps) const {
-    int ap = WRAP(bp-1, l.n),
-        cp = WRAP(bp+1, l.n);
+bool SContour::IsEar(int ap, int bp, int cp, double scaledEps) const {
 
     STriangle tr = {};
     tr.a = l[ap].p;
@@ -305,17 +303,82 @@ void SContour::UvTriangulateInto(SMesh *m, SSurface *srf) {
     }
     l.RemoveTagged();
 
+    // Handle simple triangle fans all at once.
+    if(srf->degm == 1 && srf->degn == 1) {
+        l.ClearTags();
+        int j=0;
+        int pstart = 0;
+        double elen = -1.0;
+        double oldspan = 0.0;
+        for(i = 1; i < l.n; i++) {
+            Vector ab = l[i].p.Minus(l[i-1].p);
+            // first time just measure the segment
+            if (elen < 0.0) {
+                elen = ab.Dot(ab);
+                oldspan = elen;
+                j = 1;
+                continue;
+            }
+            // check for consecutive segments of similar size which are also
+            // ears and where the group forms a convex ear
+            bool end = false;
+            double ratio = ab.Dot(ab) / elen;
+            if ((ratio < 0.25) || (ratio > 4.0)) end = true;
+
+            double slen = l[pstart].p.Minus(l[i].p).MagSquared();
+            if (slen < oldspan) end = true;
+
+            if (!IsEar(i-2, i-1, i, scaledEps) ) end = true;
+            if ((j>0) && !IsEar(pstart, i-1, i, scaledEps)) end = true;
+            if (i == l.n-1) end = true;
+
+            if (!end) {
+                j++;
+                oldspan = slen;
+            } else {
+                if (j > 3) {
+                    Vector center = l[pstart+1].p.Plus(l[pstart+j-1].p).ScaledBy(0.5);
+                    for (int x=0; x<j; x++) {
+                        STriangle tr = {};
+                        tr.a = center;
+                        tr.b = l[pstart+x].p;
+                        tr.c = l[pstart+x+1].p;
+                        m->AddTriangle(&tr);
+                    }
+                    for (int x=1; x<j; x++) {
+                        l[pstart+x].tag = 1;
+                    }
+                    STriangle tr = {};
+                    tr.a = center;
+                    tr.b = l[pstart+j].p;
+                    tr.c = l[pstart].p;
+                    m->AddTriangle(&tr);    
+                }
+//                pstart += j;
+                pstart = i-1;
+                elen = ab.Dot(ab);
+                oldspan = elen;
+                j = 1;
+            }
+        }
+        l.RemoveTagged();
+    }
+
     // Now calculate the ear-ness of each vertex
     for(i = 0; i < l.n; i++) {
-        (l[i]).ear = IsEar(i, scaledEps) ? EarType::EAR : EarType::NOT_EAR;
+        int ap = WRAP(i-1, l.n),
+            cp = WRAP(i+1, l.n);
+        (l[i]).ear = IsEar(ap, i, cp, scaledEps) ? EarType::EAR : EarType::NOT_EAR;
     }
 
     bool toggle = false;
     while(l.n > 3) {
         // Some points may have changed ear-ness, so recalculate
         for(i = 0; i < l.n; i++) {
+            int ap = WRAP(i-1, l.n),
+                cp = WRAP(i+1, l.n);
             if(l[i].ear == EarType::UNKNOWN) {
-                (l[i]).ear = IsEar(i, scaledEps) ?
+                (l[i]).ear = IsEar(ap, i, cp, scaledEps) ?
                                         EarType::EAR : EarType::NOT_EAR;
             }
         }