[MOAB-dev] create ray_intersect_all_sets function

[Paul Wilson]

Hi all,

I am not sure how this is different from calling ray_intersect_sets 
multiple times, one after the other?  This would march along the ray and 
find all the intersections. Is it just a performance issue?

Paul

Hongjun Kim wrote:
> Your patch is working for me.
> Are you going to commit it or do you want me to do it?
> Thanks.
>
> Hong-Jun
>
> ----- Original Message -----
> From: "Jason Kraftcheck" <kraftche at cae.wisc.edu>
> To: hongjun at mcs.anl.gov
> Cc: "Brandon Smith" <bsmith82 at yahoo.com>, moab-dev at mcs.anl.gov
> Sent: Monday, April 5, 2010 3:00:14 PM GMT -06:00 US/Canada Central
> Subject: Re: [MOAB-dev] create ray_intersect_all_sets function
>
> hongjun at mcs.anl.gov wrote:
>
>
>   
>> To find all surface sets intersected (including multiple hits for one
>> surface set), I have to give large tolerance. If it is not, it just find
>> the first intersections for each surface set.
>>
>>     
>
> Specifying a large tolerance to obtain all intersections is a suboptimal
> solution.  You might as well just test all of the triangles against the ray.
>
> However, rather than adding 200 lines of duplicated functionality, why not
> just fix the existing code such that it can return multiple intersections.
> For example, see the attached patch.
>
> - jason
>
>
> Index: src/OrientedBoxTreeTool.cpp
> ===================================================================
> --- src/OrientedBoxTreeTool.cpp	(revision 3740)
> +++ src/OrientedBoxTreeTool.cpp	(working copy)
> @@ -950,6 +950,14 @@
>  
>  void RayIntersectSets::add_intersection( double t, EntityHandle facet )
>  {
> +    // If minTolInt is less than zero, return all intersections
> +  if (minTolInt < 0 && t > -tol) {
> +    intersections.push_back(t);
> +    sets.push_back(lastSet);
> +    facets.push_back(facet);
> +    return;
> +  }
> +
>      // Check if the 'len' pointer is pointing into the intersection
>      // list.  If this is the case, then the list contains, at that
>      // location, an intersection greater than the tolerance away from
> Index: src/moab/OrientedBoxTreeTool.hpp
> ===================================================================
> --- src/moab/OrientedBoxTreeTool.hpp	(revision 3740)
> +++ src/moab/OrientedBoxTreeTool.hpp	(working copy)
> @@ -233,6 +233,9 @@
>       *                     ray start point is less than this number, the next closest
>       *                     intersection.  If the desired result is only the closest
>       *                     intersection, pass zero for this argument.
> +     *                     This function will return all intersections, regardless
> +     *                     of distance from the start of the ray, if this value
> +     *                     is negative.
>       *\param tolerance     The tolerance to use in intersection checks.
>       *\param ray_point     The base point of the ray.
>       *\param unit_ray_dir  The ray direction vector (must be unit length)
>
>   

-- 
Paul Wilson

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