CGAL users discussion list

[Pol Monsó Purtí <>]

Hello Laurent, thanks for the interest.

To my understanding the difference between Gt:: and K:: iso_rectangle_2s and Segment_2s is that they have a 3d coordinate stored. We could compute the 2d intersection of the plane-projected Iso_rectangle_2 and Segment_2 just as with the K kernel, ignoring the z coordinate. The intersection then would have an invalid z, (say 0), but that's fine with me.

I believe that's what the other 2d algorithms do. Refining a triangulation does that, for example. The 3d output is useless because it has many points at z=0, but in 2d is good.

I hope I understood your remark correctly.... I wasn't sure what you meant.

Cheers!

Pol

On Mon, Aug 1, 2016 at 5:43 PM, Laurent Rineau <> wrote:

That is not a bug. `CGAL::Projection_traits_xy_3` is not documented as a model of the `Kernel` concept, but only a model of a few concepts, used mostly by 2D triangulations.

http://doc.cgal.org/latest/Kernel_23/classCGAL_1_1Projection__traits__xy__3.html

Let's imagine we want to add that intersection functionality to it, how would you implement that intersection?

On 07/29/2016 04:21 PM, Pol Monsó Purtí wrote:

This won't compile:
    CGAL::Iso_rectangle_2<Gt> isor;

    CGAL::Segment_2<Gt> seg;

    auto result = CGAL::intersection(seg, isor);

with Gt = CGAL::Projection_traits_xy_3<K>

This will:

    CGAL::Iso_rectangle_2<K> isor2;

    CGAL::Segment_2<K> seg2;

    auto result2 = CGAL::intersection(seg2, isor2);

On Fri, Jul 29, 2016 at 4:09 PM, Pol Monsó Purtí <> wrote:

How can I interesect an Iso_rectangle_2 and Segment_2 using CGAL::intersection() ? I get a lot of errors regarding its definition. I believe the most rellevant is:

Iso_rectangle_2 is not a member of CGAL::Projection_traits_xy_3<K>

At the intersection line I get the error:

cannot convert from 'const CGAL::Iso_rectangle_2<portho::cgal_utils::Gt>' to 'const CGAL::Bbox_3'

The Segment_2 comes from a CGAL::Polygon_2<Gt>::Segment_2.

I've tried defining Iso_rectangle_2 as

CGAL::Iso_rectangle_2<Gt> as well as Gt::Iso_rectangle_2

CGAL::intersect() documentation says Iso_rectangle_2 and Segment_2 are accepted.

If I can't figure it out I'll just create a copy of the segment and the iso rectangle based on K instead of Gt