[x3d-public] [X3D-Public] camera, random path on a sphere

[Don Brutzman]

On 11/29/2015 5:08 PM, Andreas Plesch wrote:
> On November 29, 2015, at 2:01 PM, x3d-public-request at web3d.org wrote:
>[...]
> John,
>
> I added an SFBool option onGreatCircle for GeoPositionInterpolator in x3dom when I implemented the node. This is non-standard. The standard says somewhere that interpolators interpolate linearly.
>
> Not sure how this can be used in a non-geospatial scene, however, especially without a script node. I guess you could use the geocentric geoSystemand wrap the viewpoint in a transform to scale it down to how you need it. For example, to get positions on a sphere of 10  m radius you would need to divide coordinates by ca. 637000.
>
> It might also work to  just provide non-geospatial coordinates to GeoPositionInterpolatorwith the GCgeoSystemas long as they are located on a sphere centered at the origin. The interpolated coordinates should still be on the same sphere.
>
> Cobweb does not support geospatial last time I checked.

onGreatCircle sounds like an interesting addition... though wondering what would be the alternative?

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25.3.7 GeoPositionInterpolator
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geodata.html#GeoPositionInterpolator
[...]
The geovalue_changed field outputs the the interpolated coordinate in the spatial reference frame specified by geoSystem. This can be passed to other GeoX3D nodes that support a field of this form (e.g., GeoViewpoint and GeoLocation).
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I would interpret "in the spatial reference frame" to imply great-circle travel, since dipping underground is usually suboptimal...

Sounds like a good topic for geospatial working group to consider.  Please submit a spec comment if there are plausible alternatives that such a field might indicate.  Thanks for your efforts.

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