CGAL users discussion list

[Joachim Reichel <>]

Hi,

> I've found a problem when rendering Polyhedron in opengl environment:
> When the number of vertices of the mesh rendered is big, then it'll be very

what is "big"? 10000? 100000? 1 million?

> slow when manipulating it (translate, rotation or scale) in the window,
> wheras i've found that the manipulation in other software(eg. meshlab) for
> the same mesh is much faster.
> Has anyone else found the same problem?
> I attached my code of rendering as follows, could anyone give me some
> suggestions on speeding it up pls?
> 
> void render(Polyhedron * pmesh)
> {
>   for ( Facet_iterator i = pmesh->facets_begin(); i != pmesh->facets_end();
> i++)
>  {
>      glBegin(GL_POLYGON);
>      Halfedge_around_facet_circulator j = i->facet_begin();
>     do 
>    {
>       glNormal3f(j->vertex()->normal().x(),
>       j->vertex()->normal().y(),
>       j->vertex()->normal().z());
> 
>      glVertex3f(j->vertex()->point().x(),
>       j->vertex()->point().y(),
>       j->vertex()->point().z());
>    } while(++j != i->facet_begin());
>     glEnd();
>  }
> }

it might help if you bind repeated expressions like j->vertex()->normal() to a
const reference.

But I guess you get the most benefit by using OpenGL display lists and/or
vertex arrays. See http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=12
and http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=45 for examples.

Joachim