GeoVRML question 
Author Message
 GeoVRML question

Hi,

Using GeoVRML, I have GeoLocated an aerial photograph on a GeoElevation
of the earth.  Using GeoViewpoint I can look at the earth from far away,
but I'd like to zoom into the photograph, also using GeoViewpoint.  

The problem is when I set the GeoViewpoint to be close enough to view
the photograph, it gets clipped by the near clipping plane (I think).  

Is there anyway to get in real close to see small details in GeoVRML?
I'm using Cosmo Player.

Thanks,

--
Robert Lipman                  
National Institute of Standards and Technology (NIST)
Building and Fire Research Laboratory
Computer-Integrated Construction Group
100 Bureau Drive, Stop 8630
Gaithersburg, Maryland  20899-8630


fax: (301) 975-5433       http://www.*-*-*.com/



Mon, 18 Aug 2003 03:47:39 GMT  
 GeoVRML question

Hi Robert,

The problem here is that because of the vast change in scale implicit in
flying from outer space down to ground level, you would need to update the
near/far clipping planes as you fly down. You would also probably want to
update the speed field as you navigate too so that you can implement
altitude-dependent velocity, i.e. you need to travel very fast in space in
order to generate the same apparent velocity, or optical flow, that you do
flying a few meters above the earth's surface.

In the case of continually updating the speed field, I recall that this
didn't work under Cosmo because of a rather annoying feature that whenever
you changed the speed field of a NavigationInfo node, Cosmo also reset fields
such as the navigation type - meaning that you could never change from the
default nav mode. I don't know if the same is true of changing the near/far
planes, but it may certainly be an issue.

As a workaround, I suggest that you introduce multiple GeoViewpoint nodes.
When a GeoViewpoint node is instantiated, it will work out "good" values for
speed and clipping planes for that viewpoint. Therefore, you could have one
viewpoint for the entire earth, and one for down on the ground. Switching
between the two should select the appropriate clipping plane settings for
that viewpoint.

Cheers,

Martin.

Quote:

> Hi,

> Using GeoVRML, I have GeoLocated an aerial photograph on a GeoElevation
> of the earth.  Using GeoViewpoint I can look at the earth from far away,
> but I'd like to zoom into the photograph, also using GeoViewpoint.

> The problem is when I set the GeoViewpoint to be close enough to view
> the photograph, it gets clipped by the near clipping plane (I think).

> Is there anyway to get in real close to see small details in GeoVRML?
> I'm using Cosmo Player.

> Thanks,

> --
> Robert Lipman
> National Institute of Standards and Technology (NIST)
> Building and Fire Research Laboratory
> Computer-Integrated Construction Group
> 100 Bureau Drive, Stop 8630
> Gaithersburg, Maryland  20899-8630


> fax: (301) 975-5433      http://cic.nist.gov/lipman/
> -------------------------------------------------------------------------
> for list subscription instructions,


---------------------------------------------------------------------------
Martin Reddy                                   SRI International, AI Center
                                               Menlo Park, CA 94025-3493

http://www.ai.sri.com/~reddy                   Fax : (650) 859-3735


Mon, 18 Aug 2003 04:41:25 GMT  
 
 [ 2 post ] 

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