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- From: "Sebastien Loriot (GeometryFactory)" <>
- To:
- Subject: Re: [cgal-discuss] Intersection between a ray and a cell
- Date: Mon, 28 Jul 2014 11:25:38 +0200
- Organization: GeometryFactory
I think for each cell you only need to consider the triangle facet that
is opposite to q in all your intersection queries.
Sebastien.
On 07/28/2014 11:17 AM, Cedric Doucet wrote:
Hello Sébastien,
thank you very much for your answer.
My problem is the following: given two points p and q, find the cells which
are
1. incident to q,
2. intersected by ray (p,q)
3. NOT intersected by segment [p,q].
I do not exactly how to do that efficiently.
My (naive) algorithm is the following:
1. create a ray (p,q) and find cells incident to q which are intersected by
(p,q)
2. create a segment [p,q] and find cells incident to q which are intersected
by [p,q]
3. compute the topological intersection of sets from 1 and 2.
I managed to find cells which are incident to q using incident_cells function
from CGAL.
I also managed to construct a ray and a segment from p and q.
I now have to find which cells are intersected by (p,q) and not [p,q].
My naive algorithm consist in
1. intersectedCells = std::vector(number of incident cells to q);
2. for each incidentCellToQ do
3. for vertexIndex = 0 to 3 do
4. Triangle t = triangle(incidentCellToQ,vertexIndex);
5. if intersection(segment,t).empty() do
6. if ! intersection(segment,t).empty() do
7. intersectedCells.pushback(incidentCellToQ)
8. end if
9. end if
10. end for
11. end for
The above algorithm is not very well written (and maybe false) because I have
not finished to implement it and test it.
However, I feel that I will compute to many things.
Having a function to compute intersection between a ray and a cell could be
useful here.
Do you think there exist a more simple solution in CGAL?
Best,
Cédric
----- Mail original -----
De: "Sebastien Loriot (GeometryFactory)"
<>
À:
Envoyé: Lundi 28 Juillet 2014 10:42:27
Objet: Re: [cgal-discuss] Intersection between a ray and a cell
It's not clear to me what you are looking for (what you say about nodes
confuses me).
Is the ray arbitrary and do you want to know all the finite cells
intersected by that ray?
Sebastien.
On 07/28/2014 10:22 AM, cdoucet wrote:
Hello,
In a 3D Delaunay triangulation, I would like to know which tetraedra
(indicent to the same node) are intersected by a given ray (passing through
this node).
I found in the documentation that intersections between rays and other
cells
can be computed:
http://doc.cgal.org/latest/Kernel_23/group__intersection__linear__grp.html
However, it does not seem possible to call intersection function for a ray
and a tetrahedron (or a Cell_handle).
How could I perform such an intersection with CGAL?
Thank you very much for your help.
Cédric Doucet
Inria Paris-Rocquencourt
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- [cgal-discuss] Intersection between a ray and a cell, cdoucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Cedric Doucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Cedric Doucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, cdoucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Cedric Doucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Cedric Doucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Cedric Doucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, cdoucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Cedric Doucet, 07/28/2014
- Re: [cgal-discuss] Intersection between a ray and a cell, Sebastien Loriot (GeometryFactory), 07/28/2014
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