Re: Coordinate System and eye

• To: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Subject: Re: Coordinate System and eye
• From: Sylvain Fourny <sylvain.fourny@xxxxxxxxx>
• Date: Wed, 18 Apr 2001 12:28:37 +0200

Hi,
I'm sorry but i don't understand what can help me in this messages...
I want to use the z-buffer method to sort hidden and visible edges.
For this, I need the position of the centered eye.
I think that i must use the visad.java3d.DisplayRendererJ3D and found
the appropriate transformation but unfortunately, there is not a lot of
documentation on it...
Can you explain me the difference between :
- DisplayRendererJ3D.getTrans
and
- DisplayRendererJ3D.getViewTrans

I try to applicate this transformations in both order but i still not
found my viewPoint ?
What is the View and can I use it ?
Please help me, I'm completly lost in all this transformations...
-Sylvain-

Bill Hibbard wrote:
> 
> Hi Sylvain,
> 
> > I've got one question about Coordinate System in VisAD. What is the link
> > between the coordinate system of the samples and the coordinate system
> > of Java3d ? In fact, my question is "how to locate the centered eye ?"
> > If I use :
> >
> > Canvas3D canvas = disp_rend.getCanvas();
> > Point3d eye_position = new Point3d();
> > canvas.getCenterEyeInImagePlate(eye_position);
> >
> > I got {0,0,0}.
> > Is there a method that gives the eye position in the same coordinate
> > system as the samples ?
> 
> The maping from data coordinates to display coordinates is
> defined by the ScalarMaps to spatial DisplayRealTypes (e.g.,
> XAxis, YAxis, ZAxis). Assuming that no CoordinateSystems
> are involved, its pretty straightforward and is described in:
> 
>   http://www.unidata.ucar.edu/staff/russ/visad/msg00862.html
> 
> and:
> 
>   http://www.unidata.ucar.edu/staff/russ/visad/msg01793.html
> 
> Note that these two answers go further than what you are
> asking, and describe how to compute range values of Fields.
> 
> Cheers,
> Bill
> ----------------------------------------------------------
> Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
> hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
> http://www.ssec.wisc.edu/~billh/vis.html

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    • From: Sylvain Fourny
  • Re: Coordinate System and eye
    • From: Bill Hibbard