Implement SPolygon::TriangulateInto.

src/polygon.cpp

@@ -47,6 +47,17 @@ void STriangle::FlipNormal() {
     swap(an, bn);
 }
 
+STriangle STriangle::Transform(Vector u, Vector v, Vector n) const {
+    STriangle tr = *this;
+    tr.a  = tr.a.ScaleOutOfCsys(u, v, n);
+    tr.an = tr.an.ScaleOutOfCsys(u, v, n);
+    tr.b  = tr.b.ScaleOutOfCsys(u, v, n);
+    tr.bn = tr.bn.ScaleOutOfCsys(u, v, n);
+    tr.c  = tr.c.ScaleOutOfCsys(u, v, n);
+    tr.cn = tr.cn.ScaleOutOfCsys(u, v, n);
+    return tr;
+}
+
 STriangle STriangle::From(STriMeta meta, Vector a, Vector b, Vector c) {
     STriangle tr = {};
     tr.meta = meta;
@@ -620,7 +631,7 @@ void SPolygon::MakeEdgesInto(SEdgeList *el) const {
     }
 }
 
-Vector SPolygon::ComputeNormal() {
+Vector SPolygon::ComputeNormal() const {
     if(l.n < 1) return Vector::From(0, 0, 0);
     return (l.elem[0]).ComputeNormal();
 }
@@ -717,6 +728,17 @@ bool SPolygon::SelfIntersecting(Vector *intersectsAt) const {
     return ret;
 }
 
+void SPolygon::InverseTransformInto(SPolygon *sp, Vector u, Vector v, Vector n) const {
+    for(const SContour &sc : l) {
+        SContour tsc = {};
+        tsc.timesEnclosed = sc.timesEnclosed;
+        for(const SPoint &sp : sc.l) {
+            tsc.AddPoint(sp.p.DotInToCsys(u, v, n));
+        }
+        sp->l.Add(&tsc);
+    }
+}
+
 //-----------------------------------------------------------------------------
 // Low-quality routines to cutter radius compensate a polygon. Assumes the
 // polygon is in the xy plane, and the contours all go in the right direction

src/polygon.h

@@ -147,7 +147,7 @@ public:
     List<SContour>  l;
     Vector          normal;
 
-    Vector ComputeNormal();
+    Vector ComputeNormal() const;
     void AddEmptyContour();
     int WindingNumberForPoint(Vector p) const;
     double SignedArea() const;
@@ -161,6 +161,8 @@ public:
     void OffsetInto(SPolygon *dest, double r) const;
     void UvTriangulateInto(SMesh *m, SSurface *srf);
     void UvGridTriangulateInto(SMesh *m, SSurface *srf);
+    void TriangulateInto(SMesh *m) const;
+    void InverseTransformInto(SPolygon *sp, Vector u, Vector v, Vector n) const;
 };
 
 class STriangle {
@@ -185,6 +187,7 @@ public:
     int WindingNumberForPoint(Vector p) const;
     bool ContainsPoint(Vector p) const;
     bool ContainsPointProjd(Vector n, Vector p) const;
+    STriangle Transform(Vector o, Vector u, Vector v) const;
 };
 
 class SBsp2 {

src/srf/triangulate.cpp

@@ -502,4 +502,27 @@ void SPolygon::UvGridTriangulateInto(SMesh *mesh, SSurface *srf) {
     UvTriangulateInto(mesh, srf);
 }
 
+void SPolygon::TriangulateInto(SMesh *m) const {
+    Vector n = normal;
+    if(n.Equals(Vector::From(0.0, 0.0, 0.0))) {
+       n = ComputeNormal();
+    }
+    Vector u = n.Normal(0);
+    Vector v = n.Normal(1);
 
+    SPolygon p = {};
+    this->InverseTransformInto(&p, u, v, n);
+
+    SSurface srf = SSurface::FromPlane(Vector::From(0.0, 0.0, 0.0),
+                                       Vector::From(1.0, 0.0, 0.0),
+                                       Vector::From(0.0, 1.0, 0.0));
+    SMesh pm = {};
+    p.UvTriangulateInto(&pm, &srf);
+    for(STriangle st : pm.l) {
+        st = st.Transform(u, v, n);
+        m->AddTriangle(&st);
+    }
+
+    p.Clear();
+    pm.Clear();
+}