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<p>Hi Vijay,<br>
</p>
<br>
<div class="moz-cite-prefix">On 12/13/2016 11:03 AM, Vijay S.
Mahadevan wrote:<br>
</div>
<blockquote
cite="mid:CAOcbyd2Hk4Mm5ScsYrPOFfXc3vMH2HRSjdS3KRkuQxGfYg7K0g@mail.gmail.com"
type="cite">
<pre wrap="">Paul, IMO, if there is DagMC specific logic embedded in general ray
intersection code, and if no one has complained about it so far, my
guess is there aren't many users relying on that API. In which case,
I'm all for simplifying it.
</pre>
<blockquote type="cite">
<pre wrap="">These methods would no longer return lists of intersections, but would return them one at a time for consideration by the calling application.
</pre>
</blockquote>
<pre wrap="">
However, it is very unclear to me how a calling application would know
whether to stop querying again or if it should be satisfied once the
first successful entity is found. If there is a stronger reasoning for
this behavioral change, that would help motivate the change better.
But as I said above, if DagMC is the sole consumer of this API, do
modify it so that it is part of the next version.</pre>
</blockquote>
<br>
Conceptually there is really no difference imposed by this change.
The calling application will be asked to accept intersections one at
a time rather than getting a list all at once. As it is, the
calling application has to decide how to deal with that list (if it
has more than one entry). The simplest approach is to just add them
all to a list and end up with the same information as was originally
available.<br>
<br>
Perhaps the interface can offer both options:<br>
<ol>
<li>methods that return complete lists with not opportunity for
filtering/disambiguation and don't require a callback function<br>
</li>
<li>methods that return nothing but require a callback function to
register each intersection as they arise</li>
</ol>
<p>Paul<br>
</p>
<br>
<blockquote
cite="mid:CAOcbyd2Hk4Mm5ScsYrPOFfXc3vMH2HRSjdS3KRkuQxGfYg7K0g@mail.gmail.com"
type="cite">
<pre wrap="">
Vijay
On Tue, Dec 13, 2016 at 9:17 AM, Patrick Shriwise <a class="moz-txt-link-rfc2396E" href="mailto:shriwise@wisc.edu"><shriwise@wisc.edu></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi all,
Having seen how many other ray tracing codes operate I think that these are
valuable changes to the OrientedBoxTreeTool which will allow it to be
extended to many other applications.
Pulling out these DAGMC-specific intersection disambiguation operations into
separate functions for filtering intersections will also allow them to be
applied in other ray tracing kernels (AdaptiveKDTree, etc.) if desired.
-Patrick
Patrick C. Shriwise
Research Fellow
University of Wisconsin - Madison
Engineering Research Building - Rm. 428
1500 Engineering Drive
Madison, WI 53706
(608) 446-8173
On 12/09/2016 04:44 PM, Paul Wilson wrote:
Hello all,
I have been spending a lot of quality time with the ray_intersect_* methods
of the OrientedBoxTreeTool over the last few weeks. I think I have
(re)learned all the subtleties of the additional code that exists in
RayIntersectSets::leaf() (invoked with API function ray_intersect_sets).
In general, these are all additional tests that make sense only in the
context of a call from DagMC:
is this facet in a list of previous facets intersected by this ray prior to
this call
is this facet in a list of previous facets (or their neighborhood)
encountered during this call
is this intersection a piercing or glancing intersection as defined by
notions of surface sense known to DagMC
There is then a complex logic related to how many intersections to keep
based on three quantities: two are a "window" in which the distance to
distance to intersection must fall and the third is a count of how many
intersections to keep.
The logic for ray_intersect_triangles() includes none of this. I was
contemplating an interface change to ray_intersect_triangles() that would
add enough information to include the same tests, and modularizing those
tests to reuse code in both places. However, (a) the interface for that
would be awkward and (b) it would be imposing DagMC conventions on even more
code.
Instead I propose the reduce the interface of all ray_intersect_* methods to
include only the following:
const EntityHandle root_set: points to the root of the OBB Tree
const double tolerance: for use in searching for intersections (largely
unused at the moment, I think)
const double ray_point[3]: starting point of ray
const double unit_vector[3]: direction of ray
std::pair<double*, double*> window: window to narrow search for interesting
intersections
std::pair<double*, double*> register_intersection(...): call back function
to perform application specific filtering/disambiguation of possible
intersection, returning an updated window
These methods would no longer return lists of intersections, but would
return them one at a time for consideration by the calling application.
Since this is such a major interface change, I thought I'd solicit feedback
before embarking upon it. It won't necessarily bee that much code change,
but who knows how it impacts other possible users of this code???
Paul
--
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ --
Paul P.H. Wilson
Grainger Professor of Nuclear Engineering
608-263-0807
<a class="moz-txt-link-abbreviated" href="mailto:paul.wilson@wisc.edu">paul.wilson@wisc.edu</a>
419 Engineering Research Bldg
1500 Engineering Dr, Madison, WI 53706
calendar: <a class="moz-txt-link-freetext" href="http://go.wisc.edu/pphw-cal">http://go.wisc.edu/pphw-cal</a>
Computational Nuclear Engineering Research Group
cnerg.engr.wisc.edu
Faculty Director, Advanced Computing Initiative
aci.wisc.edu
</pre>
</blockquote>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ --
Paul P.H. Wilson
Grainger Professor of Nuclear Engineering
608-263-0807
<a class="moz-txt-link-abbreviated" href="mailto:paul.wilson@wisc.edu">paul.wilson@wisc.edu</a>
419 Engineering Research Bldg
1500 Engineering Dr, Madison, WI 53706
calendar: <a class="moz-txt-link-freetext" href="http://go.wisc.edu/pphw-cal">http://go.wisc.edu/pphw-cal</a>
Computational Nuclear Engineering Research Group
cnerg.engr.wisc.edu
Faculty Director, Advanced Computing Initiative
aci.wisc.edu</pre>
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