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[shebbycat <>]

Thanks for the response, Sebastien.  Plane_3::has_on_positive_side(origin)  seems like it will do the trick.  However when I use Exact_predicates_exact_constructions_kernel seems I can no longer convert a Polyhedron3 to a NefPolyhedron3.   My initial polyhedron is generated by Random_points_in_sphere_3 followed by a Delaunay triangulation.

At a high level I start with a Polyhedron_3 random sphere, define a clipping plane, clip, convert to Nefpolyhedron3, clip, then convert back to a Polyhedron_3 for rendering in OpenGL.    Could there be a better way of approaching this process?

From: "Sebastien Loriot (GeometryFactory) [via cgal-discuss]" <[hidden email]>
Date: Monday, September 22, 2014 at 7:23 AM
To: Scott Shebby <[hidden email]>
Subject: Re: Iterative Applications of 3D Boolean Operations on Nef Polyhedra

	On 09/21/2014 03:12 AM, shebbycat wrote:

> Hi everyone,
>
> I'm new to CGAL and quite grateful for its existence!  I've built an
> application that iteratively clips a 3D Nef Polyhedra with a plane, for a
> specific application.  For example, I define a clipping plane which
> intersects a polyhedron (with its center at 0,0,0) and clip, rotate by some
> degrees, clip again, and so on.  When its done I convert it back to a 3D
> polyhedron and render it in OpenGL.
>
> My first question is that this process is really slow.. like taking a couple
> seconds per clip.  My kernel is:
> typedef CGAL::Extended_cartesian< CGAL::Gmpq> K2;
>

Try CGAL::Exact_predicates_exact_constructions_kernel instead of K2.

Do you have a geometric properties for your set of clipping planes?
(like defining a convex volume)?


> My second question is that sometimes after my clip process Ive inadvertently
> clipped the origin side of the polyhedron instead of the "outer" side of the
> intersection.  Id like to always preserve the portion of the poly that
> contains the origin.  Ive tried grabbing the volume handle for the origin
> point, but not sure how to use it properly.

try using Plane_3::has_on_positive_side(origin)

http://doc.cgal.org/latest/Kernel_23/classCGAL_1_1Plane__3.html#a2ca90cac980833ff38dd12dcb9858baf

Sebastien.

>
> Is there anything I can do to speed the clipping up, and whats the best way
> to check that my intersection will preserve the correct side of the poly?
>
> Thanks!
>
>
>
> --
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>

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View this message in context: Re: Iterative Applications of 3D Boolean Operations on Nef Polyhedra
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