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Hi all, <br>
<br>
Are there any other thoughts on this? Or ideas on the proper steps
forward for the iGeom implementation in CGM?<br>
<br>
Cheers,<br>
<br>
Patrick<br>
<br>
<br>
<div class="moz-cite-prefix">On 02/02/2015 12:43 PM, Patrick
Shriwise wrote:<br>
</div>
<blockquote cite="mid:54CFC55E.4030202@wisc.edu" type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Hi Evan, <br>
<br>
As to 2). I completely agree and I think if I'm reading it
correctly its aligning with the second of my two purposed
solutions in the prior email. <br>
<br>
1) does seem to add a complication or two. I'm glad you brought it
up! <br>
<br>
I don't know much about how these bodies fit into the hierarchy of
CGM, but naively it seems that if they are still treated as
RefVolumes then operations on these sheets could be handled as
usual in CGM behind the iGeom interface. For the user, it might be
good to add something in iGeom which will notify them that a sheet
body/volume has been returned if it is a possibility in the
function they have called. What it looks like to me from this code
in Body.cpp<br>
<br>
CubitBoolean Body::is_sheet_body()<br>
{<br>
DLIList<RefVolume*> volumes;<br>
ref_volumes(volumes);<br>
while (volumes.size())<br>
if (!volumes.pop()->is_sheet())<br>
return CUBIT_FALSE;<br>
return CUBIT_TRUE;<br>
}<br>
<br>
is that sheet bodies are still in fact treated as RefVolumes.
However after looking at some of the OCC code, sheets in OCC come
back as OCCSurfaces. I'm assuming that these are then translated
to RefVolumes in the context of CGM, but I lack the expertise to
know exactly. Does anyone have an exact answer to this?<br>
<br>
If we can still treat RefVolumes which are sheets in the same way
as other RefVolumes then I think returning only RefVolumes is
still a valid option. If we find that this is not the case or that
it will obscure the interface by causing certain operations to be
compromised, then we might have an entirely different problem to
deal with. <br>
<br>
Cheers, <br>
<br>
Patrick <br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 01/30/2015 12:20 PM, Vander Zee,
Evan B. wrote:<br>
</div>
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">There
are two additional things that we might want to consider
in this discussion.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"><span
style="mso-list:Ignore">1)<span style="font:7.0pt
"Times New Roman""> </span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">When
are bodies that CGM is passing through the iGeom interface
allowed to be “sheet bodies?” In other words, when should
we be able to pass what are essentially 2-dimensional
entities through the iGeom interface?<o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"><span
style="mso-list:Ignore">2)<span style="font:7.0pt
"Times New Roman""> </span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">The
input path of iGeom is a consideration as well as the
output side. We can assume, I think, that the only entity
handles a user passes into methods through the iGeom
interface are entity handles that have been accessed
through the iGeom interface. If we want to allow
operations that apply to multiple volumes, but we never
pass back entity handles that refer to multiple-volume
bodies, then we should make sure that the interface
includes methods that support passing in a list of
entities or an entity set. For example, the interface
already supports subtract with entity set arguments as
well as with entity handles.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">I
think that with a little documentation, we could expect
users to be responsible for cleaning up single-entity
entity sets that are returned from operations that could
in some cases return multiple volumes. However, making it
easier to use and not expecting a lot of the user is often
the better path.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">These
are just a few comments from a guy who’s relatively new to
CGM. Please continue the discussion with comments from
more experienced developers.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">-Evan</span><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">
<a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:cgma-dev-bounces@mcs.anl.gov">cgma-dev-bounces@mcs.anl.gov</a>
[<a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="mailto:cgma-dev-bounces@mcs.anl.gov">mailto:cgma-dev-bounces@mcs.anl.gov</a>]
<b>On Behalf Of </b>shriwise<br>
<b>Sent:</b> Friday, January 30, 2015 9:15 AM<br>
<b>To:</b> Paul Wilson; CGMA Development<br>
<b>Subject:</b> Re: [cgma-dev] Continuing discussion
of iGeom handling of RefVolume vs Body<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><br>
<br>
Hi all,<br>
<br>
From an iGeom perspective, I'm not sure that using bodies is
a bad thing... The real issue to me is the mix currently
being used. It has been shown to cause problems in iRel. In
any case, I think that we should move entirely to one or the
other. <br>
<br>
The real issue to me is that outside of the user's knowledge
of the geometry, they can't be sure if the body they are
getting from UniteEnts, IntersectEnts, etc. contains
disjoint volumes or not. <br>
<br>
<b><u>Using RefVolumes Exclusively</u></b><br>
As it currently stands in specification, in the iGeom
interface there is no notion of a body or, perhaps more
importantly, an Entity which <i>contains</i> other
entities. There are only Entities and EntitySets. The point
being that returning a recast cgm Body as an Entity from
iGeom simply shouldn't be allowed as it breaks established
conventions of iGeom unless we do one of two things:<br>
<br>
1) Only return bodies as EntitySets which contain the
appropriate Entities (these relationships being set within
the functions being called.)<br>
- This would require <br>
<br>
2) Return arrays of Entities from functions when
appropriate, along with an indicator of the array size.<br>
<br>
Either way, a proper iGeom implementation will require a bit
of a deeper look at any function that currently returns a
Body to determine the proper way to handle this. For
example, the createSphere function should really return a
single RefVolume as the body created from this process
wouldn't be expected to have more than one volume. However,
I think that other functions like uniteEnts and so on will
require something like 1) or 2) above. <br>
<br>
<b><u>Using Bodies Exclusively</u></b><br>
All this being said about RefVolumes, it would certainly be
possible to always return Bodies from iGeom for dimension 3
entities, but as I mentioned above I think this should
always be done using EntitySets. This implementation would
be less clean as iGeom models would then perhaps contain
many EntitySets most of which really only contain one
entity. The user would then have to retrieve their created
entities proper by querying the EntitySets. It adds an
unnecessary level of abstraction and might cloud the user's
idea of what EntitySets are intended for.<br>
<br>
One last thing I'll say in favor of using RefVolumes
exclusively but returning lists is that it adds clarity to
the interface. By having boolean functions like uniteEnts
and others return lists or EntitySets, it will imply to the
user that iGeom is capable of doing these operations in the
case of disjointed volumes and that they may be getting
multiple volume entities back from these functions. If we
were to return bodies only, it then becomes ambiguous (and
perhaps confusing to the user) as to whether or not any
function called is returning one or more volumes. <br>
<br>
That's my take. Apologies for the lack of insight in the
changes found in the current PR. The situation is not as
simple as I'd initially thought. <br>
<br>
Cheers, <br>
<br>
Patrick <o:p></o:p></p>
<div>
<p class="MsoNormal">On 01/29/2015 03:17 PM, Paul Wilson
wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Hello,<br>
<br>
There has been some discussion in a <a
moz-do-not-send="true"
href="https://bitbucket.org/fathomteam/cgm/pull-request/8/igeom-updates">
pull request</a> that I thought would be better brought
to the mailing list.<br>
<br>
This was initially motivated by the realization that iGeom
was inconsistent in returning a RefVolume vs a Body in
different calls. Thus, two entity handles that referred
to the same volume in space would not be detected as the
same volume.<br>
<br>
Faced with two choices - refer only to RefVolumes or refer
only to Body's - we settled on referring only to
refVolume's in the iGeom interface. However, this breaks
the ability to refer to a Body such as my be returned by
uniting two volumes that are disjoint - which is part of
the interface.<br>
<br>
So.... perhaps we need to only deal with Body in the iGeom
interface. Perhaps Patrick can offer some of the
downsides to this approach?<br>
<br>
Paul<br>
<br>
<br>
<o:p></o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ --<o:p></o:p></pre>
<pre>Paul Wilson ~ UW-Madison ~ 608-263-0807 ~ cal: <a moz-do-not-send="true" href="http://bit.ly/pphw-cal">http://bit.ly/pphw-cal</a><o:p></o:p></pre>
<pre>Professor, Engineering Physics. ~ <a moz-do-not-send="true" href="http://cnerg.engr.wisc.edu">http://cnerg.engr.wisc.edu</a><o:p></o:p></pre>
<pre>Faculty Director, Advanced Computing Infrastructure ~ <a moz-do-not-send="true" href="http://aci.wisc.edu">http://aci.wisc.edu</a> <o:p></o:p></pre>
</blockquote>
<p class="MsoNormal"><br>
<br>
<o:p></o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>Patrick C. Shriwise<o:p></o:p></pre>
<pre>Research Assistant<o:p></o:p></pre>
<pre>University of Wisconsin - Madison<o:p></o:p></pre>
<pre>Engineering Research Building - Rm. 428<o:p></o:p></pre>
<pre>1500 Engineering Drive<o:p></o:p></pre>
<pre>Madison, WI 53706<o:p></o:p></pre>
<pre>(608) 446-8173<o:p></o:p></pre>
</div>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Patrick C. Shriwise
Research Assistant
University of Wisconsin - Madison
Engineering Research Building - Rm. 428
1500 Engineering Drive
Madison, WI 53706
(608) 446-8173
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Patrick C. Shriwise
Research Assistant
University of Wisconsin - Madison
Engineering Research Building - Rm. 428
1500 Engineering Drive
Madison, WI 53706
(608) 446-8173
</pre>
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