Constructor for Trafo by rotation along an arbitrary axes, combine trafos

libsrc/gprim/transform3d.cpp

@@ -163,7 +163,31 @@ ostream & operator<< (ostream & ost, Transformation3d & trans)
   return ost;
 }
 
+  template <>
+  Transformation<3> :: Transformation (const Point<3> & c, const Vec<3> & axes, double angle)
+  {
+    Vec<3> vc(c);
+    Transformation<3> tc(vc);
+    Transformation<3> tcinv(-vc);
+    Transformation<3> r, ht, ht2;
 
+    // r.SetAxisRotation (3, alpha);
+    Vec<3> naxes = axes;
+    naxes.Normalize();
+    Vec<3> n1 = naxes.GetNormal();
+    Vec<3> n2 = Cross(naxes, n1);
+    r.v = Vec<3>(0,0,0);
+    double co = cos(angle);
+    double si = sin(angle);
+    for (int i = 0; i < 3; i++)
+      for (int j = 0; j < 3; j++)
+        r.m(i,j) = naxes(i)*naxes(j) + co*(n1(i)*n1(j)+n2(i)*n2(j)) + si*( (n2(i)*n1(j)-n2(j)*n1(i)) );
+
+    ht.Combine (tc, r);
+    Combine (ht, tcinv);
+  }
+
+  
   template <int D>
   Transformation<D> :: Transformation (const Point<D> * pp)
   {

libsrc/gprim/transform3d.hpp

@@ -102,6 +102,8 @@ public:
       m(i,i) = 1;
   }
 
+  Transformation (const Point<D> & c, const Vec<3> & axes, double angle);
+  
   // rotation with ...
   Transformation (const Point<D> & c, double alpha, double beta, double gamma)
   {

libsrc/meshing/python_mesh.cpp

@@ -184,7 +184,10 @@ DLL_HEADER void ExportNetgenMeshing(py::module &m)
            ([] (double x, double y) { return Vec<2>(x,y); }));
 
   py::class_<Transformation<3>> (m, "Trafo")
-    .def(py::init<Vec<3>>())
+    .def(py::init<Vec<3>>(), "a translation")
+    .def(py::init<Point<3>,Vec<3>,double>(), "a rotation given by point on axes, direction of axes, angle")
+    .def("__mul__", [](Transformation<3> a, Transformation<3> b)->Transformation<3>
+         { Transformation<3> res; res.Combine(a,b); return res; })
     .def("__call__", [] (Transformation<3> trafo, Point<3> p) { return trafo(p); })
     ;