<div dir="ltr"><div dir="auto"><div data-smartmail="gmail_signature" dir="auto"> </div><div data-smartmail="gmail_signature" dir="auto">Thanks, a few more questions:</div><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Sat, Feb 1, 2020, 8:57 PM Don Brutzman <<a href="mailto:brutzman@nps.edu" rel="noreferrer" target="_blank">brutzman@nps.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
<br>...</blockquote></div><div class="gmail_quote" dir="auto"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
> * X3D Architecture, 10.2.2 Bounding boxes<br>
> <a href="https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/group.html#BoundingBoxes" rel="noreferrer noreferrer noreferrer" target="_blank">https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/group.html#BoundingBoxes</a><br>
> <br>
> "The bounding box shall be large enough at all times to enclose the union of the group's children's bounding boxes;"<br>
> <br>
> so we should be good on that score. Note the "at all times" above which seems to apply that actual bounding box sizes always get displayed.<br>
> <br>
> <br>
> An empty group has an actual bbox size of 0. How could such a bbox be displayed ? A point ?<br>
> Or by nothing ?<br>
<br>
An empty Group (or Inline or whatever) might still have positive bboxCenter and bboxSize values specified by the author, in the original scene, perhaps in anticipation of animation changes.<br></blockquote></div><div dir="auto"><br></div><div dir="auto">Yes, so if specified, those values should be used, not computed ones. But what about the case where the size is not specified, and there is no geometry, eg a computed size would be 0?</div><div dir="auto"><br></div><div class="gmail_quote" dir="auto"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
> > X3D defines the bounding box aligned with local coordinate system:<br>
> > <a href="https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/group.html#BoundingBoxes" rel="noreferrer noreferrer noreferrer" target="_blank">https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/group.html#BoundingBoxes</a><br>
> > If the appearance of a display bounding box is left unspecified, then<br>
> > it would make sense to also allow display as world axis aligned<br>
> > bounding boxes.<br>
> <br>
> Added ", so that both are aligned with world coordinates" as follows:<br>
> <br>
> If "both" is referring to bbox and associated geometry, then it is unclear why aligning geometry is mentioned.<br>
> <br>
> Aligning the bbox with world axes would mean that all displayed bboxes have the same orientation which could be helpful. The drawback is that the orientation of the geometry would be hidden.<br>
<br>
The goal is simply to have the browser display a bounding box around the rendered geometry.<br>
<br>
Here it is again:<br>
<br>
> ======================================<br>
> <a href="https://www.web3d.org/member-only/mantis/view.php?id=1277" rel="noreferrer noreferrer noreferrer" target="_blank">https://www.web3d.org/member-only/mantis/view.php?id=1277</a><br>
> <br>
> 10.3.1 X3DBoundedObject<br>
> <br>
> SFBool [in out] displayBBox FALSE<br>
> <br>
> "When displayBBox is true, the bounding box is displayed for the associated geometry, so that both are aligned with world coordinates. The bounding box is displayed regardless of whether contained content is visible."<br>
> ======================================<br>
[...]<br>
<br>
Perhaps better:<br>
<br>
"When displayBBox is true, the bounding box is displayed for the associated geometry. The bounding box is displayed regardless of whether the associated geometry is visible."<br>
<br>
Phrasing improvements and complete clarity is always welcome. 8)<br></blockquote></div><div dir="auto"><br></div><div dir="auto">I was trying to raise the question of the orientation of the displayed bbox. In principle, there are multiple ways to compute a bbox: tightest fit or axis aligned, where the axes could be from the local or the world coordinate system. The x3d bbox is defined as axis aligned with the local coordinate system. So in a more narrow sense the display would just follow the definition and show the bbox in the orientation of the local coordinate system. But in a broader sense the display may be thought of as separate from the definition, since there is no very specific guidance on how to display the bbox. In this case, the bbox could be displayed as being aligned with world coordinate axes. This would make for a more uniform look if many bbox are displayed.</div><div dir="auto"><br></div><div>Here is a suggestion for wording:</div><div dir="auto"><br></div><div dir="auto"> "When displayBBox is true, the bounding box
for the associated geometry is displayed
aligned with the local coordinate system. If no geometry is associated, the display is undefined. The bounding box is displayed regardless of whether the associated geometry is visible."<br></div><div dir="auto"><br></div><div dir="auto"><br></div><div class="gmail_quote" dir="auto"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
all the best, Don<br>
-- <br>
Don Brutzman Naval Postgraduate School, Code USW/Br <a href="mailto:brutzman@nps.edu" rel="noreferrer noreferrer" target="_blank">brutzman@nps.edu</a><br>
Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA +1.831.656.2149<br>
X3D graphics, virtual worlds, navy robotics <a href="http://faculty.nps.edu/brutzman" rel="noreferrer noreferrer noreferrer" target="_blank">http://faculty.nps.edu/brutzman</a><br>
</blockquote></div></div>
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