CGAL users discussion list

[Efraim Fogel <>]

You need to use exact-predicate and exact-construction kernel.
When you attach code, attach it in a way that it can be compiled and 
executed, and perhaps even read by a human being.

Yue Biek wrote:
> My OS is win7(32bit) and environment is  VS2008,When I used 
> the MinKowski_2 in CGAL_3.8, I found the Union operation of two 
> Boundarys is something wrong.
>
> the function are usd in Minkowski_sum_decomp_2.h
> *The exact line is :*
> sum_holes = unite(boundary_segments.begin(), 
> boundary_segments.end(),sum_bound, sum_holes);
>
> My target is to morph between two non-convex but simple polygons.
> At first,when I morph between a triangle and a rectangle,the "unite" 
> operation is right.and the morph process is right.
> However,when the input are two non-convex polygons(PandQ.dat),though 
> the MinKowski sums of the two polygons can be calcuated, the "unite" 
> operation are something wrong. when the input are two non convex 
> polygons, the "unite" operation are right the in the first time,but in 
> the second time ,it fails.
>
> Part of source code are here,Polygon P and Polygon Q are defined 
> before hand,and they are all non-convex and simple(PandQ.dat).
>
>      glClear(GL_COLOR_BUFFER_BIT);
> float delt=0.11;
> while(true)
> {
> for(float t=0.1;t<=0.9;t+=delt)
> {
> glClear(GL_COLOR_BUFFER_BIT);
> Polygon s_temp;
> Polygon t_temp;
>
> for(size_t i=0;i!=P.size();i++)
> {
> double temp_x=P[i].x()*(1-t);
> double temp_y=P[i].y()*(1-t);
> Point temp_p(temp_x,temp_y);
> s_temp.push_back(temp_p);
> }
>
> for(size_t i=0;i!=Q.size();i++)
> {
> double temp_x=Q[i].x()*t;
> double temp_y=Q[i].y()*t;
> Point temp_p(temp_x,temp_y);
> t_temp.push_back(temp_p);
> }
>
> Polygon_with_holes sum=minkowski_sum_2(s_temp,t_temp,ssab_decomp);
>                                 
>                                 std::cout << "P = "; print_polygon 
> (s_temp);
> std::cout << "Q = "; print_polygon (t_temp);
> std::cout << "P (+) Q = ";print_polygon(sum.outer_boundary());
>
> if(!sum.is_unbounded())
> {
> glBegin(GL_LINE_LOOP);
> for(Polygon::iterator 
> cur=sum.outer_boundary().vertices_begin();cur!=sum.outer_boundary().vertices_end();cur++)
> {
>   glVertex2f(cur->x(),cur->y());
> }
> glEnd();
> glFlush();
> }
> else
> {
> for (Polygon_with_holes::Hole_iterator 
> iter=sum.holes_begin();iter!=sum.holes_end();++iter)
> {
> Polygon::iterator piter=iter->vertices_begin();
> glBegin(GL_LINE_LOOP);
> for(;piter!=iter->vertices_end();piter++)
> {
> double temp_x=piter->x();
> double temp_y=piter->y();
> glVertex2f(temp_x,temp_y);
> }
> glEnd();
> }
> }
> sum.clear();
> s_temp.clear();
> t_temp.clear();
> if(s_temp.is_empty())
> {
> cout<<"empty "<<endl;
> }
> if(t>1.0||t<0.1)
> {
> delt=-delt;
> }
> }
> }


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