[x3d-public] HUD Proto example clarification

Andreas Plesch andreasplesch at gmail.com
Mon Oct 24 19:50:24 PDT 2016


On Oct 24, 2016 5:37 PM, "Don Brutzman" <brutzman at nps.edu> wrote:
>
> On 10/24/2016 7:41 AM, Andreas Plesch wrote:
>>
>> Looking for nice Protos to check out, I came across the HUD proto here:
>>
>>
http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter14-Prototypes/HeadsUpDisplayPrototypeIndex.html
>
>
> Thanks for the feedback.  Several side-effect issues
noticed/fixed/uploaded.
>
> Must say that Cobweb response is excellent, with no apparent jerkiness
whatsoever when navigating.  Far better than some players I've seen - for
example BS Contact is very wiggly.  Instant Reality is OK (but it neglects
to load the relative image for a nearby Inline when running on localhost).

Interesting, could not really be cors related?

>
http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter14-Prototypes/HeadsUpDisplayExampleCobweb.html
>
>
>> Comments explains that its screenOffset field is the offset position for
HUD relative to current view location.
>>
>> But, in fact, screenOffset seems to be the offset relative to the local
coordinate system within which the ProtoInstance is used. For example, the
example instance has a Z offset of -5 which puts it (sensibly) in front of
the current viewpoint at -10, not behind it at -15.
>>
>> Is that understanding correct ?
>
>
> Yes.  The appinfo for screenOffset assumes that the HUD is at the top
level of the scene, and the current view location is wherever the user has
navigated.  So the screenOffset is in that local coordinate system.

Ok. I start to see the intention.

> Suggestion for a better description?  Perhaps a warning to avoid nesting?

I thought the way to use the proto screenOffset actually relative to the
viewpoint location would be to have a viewpoint position of 0 0 0 and wrap
both in a Transform which seemed like a good solution but perhaps the
ProximitySensors offsets would not be correct then.

I would suggest to revise the screenOffset appinfo to refer to the local
coordinate system ? Or simply "Initial position; resulting offset to view
location is maintained." ?

> Meanwhile the other example has a "twist in the knickers" - aha incorrect
ExternProtoDeclare reference - now fixed.
>
>
http://X3dGraphics.com/examples/X3dForWebAuthors/Chapter14-Prototypes/HudKelpForestIndex.x3d
>
> These changes are checked into sourceforge... some delays uploading, will
likely occur later tonite.
>
> all the best, Don
> --
> Don Brutzman  Naval Postgraduate School, Code USW/Br
brutzman at nps.edu
> Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA
 +1.831.656.2149
> X3D graphics, virtual worlds, navy robotics
http://faculty.nps.edu/brutzman
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