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NNTP-Posting-Date: Mon, 01 Oct 2012 07:31:59 -0500
From: David Fanning <n...@idlcoyote.com>
Newsgroups: comp.lang.idl-pvwave
Subject: Re: 3d device coordinates from a 3D polyline....
Date: Mon, 1 Oct 2012 06:31:59 -0600
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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.")