CGAL users discussion list

[Pierre Alliez <>]

 dear Kyewong,

if your mesh is static you should clearly use VBOs (vertex buffer 
objects) - this can be at least 10 times faster.

in a first preprocessing step you can create the VBOs - something like

glGenBuffers(...);

// for each VBO...
float *pData = new float[...];
// fill data here
// load data to the graphics card
glBindBuffer(GL_ARRAY_BUFFER, ...);
glBufferData(GL_ARRAY_BUFFER, size, pData, GL_STATIC_DRAW);
delete [] pData;

then in the rendering loop call something like

    for(i=0;i<nb_vbos;i++)
    {
        ::glEnableClientState(GL_VERTEX_ARRAY);
        glBindBuffer(GL_ARRAY_BUFFER, ... vbo ids);
        glVertexPointer(3, GL_FLOAT, 0, 0); // adjust to triangle mesh
        glDrawArrays(GL_POINTS, begin, count);
        ::glDisableClientState(GL_VERTEX_ARRAY);
    }

we let you check a tutorial on VBOs.


Pierre

Pierre Alliez
INRIA Sophia Antipolis - Mediterranee
Project-team GEOMETRICA
http://www-sop.inria.fr/members/Pierre.Alliez/
Tel: +33 4 92 38 76 77
Fax: +33 4 97 15 53 95


Le 26/09/2010 17:42, kyewong a écrit :
> Hi all
> 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
> 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();
>   }
> }