CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Ravi Kumaran wrote:
>  
> > This is not easily doable
> > (this imply hacks on non-documented stuff, and I am not even sure it will 
> > work as expected).
>
> > If you describe why you need "color" in faces (and what expect in the
> > output), we may provide an alternative solution
> .
> Thanks for the response. I've a small CAD program that shows different solid 
> shapes which have different user selected colors. User can fuse more than one 
> such solids with each other, I try to accomplish that by converting the solid 
> polyhedra to Nef polyhedra and then performing union operation. Since there 
> is no way to maintain the color information of faces as they pass through Nef 
> polyhedra operations, the final solid will have to be shown in a single 
> arbitrary color. This is not a big problem if the user's ultimate goal is 
> mainly solid modelling or 3D printing. But the colors are important if the 
> goal is 3D scene design/ visual effects etc.
To me it is not clean if you need a color information per face or per
solid?

> Could you point me in any particular direction, regarding the possible hack 
> you mentioned?
Hard to say. Don't even know if this is doable.
Consider the case of two cubes sharing a 2D-face, if you do a union
operation the result will contains only 6 facets (the nef polyhedron 
have remove a superfluous edge).


> Thanks.
> --
> Ravi