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Date: Mon, 1 Oct 2012 10:07:21 -0700 (PDT)
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Subject: Re: 3d device coordinates from a 3D polyline....
From: George.millw...@yahoo.com
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On Monday, October 1, 2012 6:32:00 AM UTC-6, David Fanning wrote:
> George.millw...@yahoo.com writes: 
> 
> 
> 
> > I have am idlgrpolyline which I can rotate in a 3D view (with the trackball).
> 
> > I want to know the 2D coordinates of this line in the device (ie,the 2D the projection in the window).  Can't figure it out.
> 
> 
> 
> I'm no expert in this area, but I think the 3D to 2D 
> 
> conversions of the transformation matrix (which you
> 
> can recover from the trackball) are well known. You
> 
> can read the answer at the bottom of this article,
> 
> for example:
> 
> 
> 
>    http://math.stackexchange.com/questions/336/why-are-3d-
> 
> transformation-matrices-4x4-instead-of-3x3
> 
> 
> 
> Cheers,
> 
> 
> 
> David
> 
> 
> 
> 
> 
> -- 
> 
> David Fanning, Ph.D.
> 
> Fanning Software Consulting, Inc.
> 
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
> 
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")


Hmm,

So there is nothing in the object graphics system like the 'CONVERT_COORD' routine ?

George.