Re: geomview

[slevy]

> From eps at Princeton.EDU Sun Apr 12 11:19:13 1992
> Date: Sun, 12 Apr 92 12:19:10 -0400
> From: Elisha Sacks <eps at Princeton.EDU>
> To: slevy at geom
> Subject: geomview
> 
> Hi,
> 
> I decided to work without normalization.  Now I'd like to place the initial
> camera somewhere other than the default position.  What is the syntax of the
> camera command?  I don't see documentation for it.  For example, suppose I
> want to see the 20 cube centered at the origin.
> 
> thanks,
> elisha.

Um, right, there's no documentation yet for the camera command.
If you won't need to move the camera, it might be easiest to
load a sample object, manually position the camera (using fly & orbit modes,
not moving the object, of course) to some nice-looking spot,
use the Save State button (or ">" key) to dump the viewer
state into a file, and use a text editor to extract the (camera ...)
command.  That's what I did to make an animation recently.

An alternative would be to construct a camera-to-world matrix explicitly.

The matrix maps camera coordinates, with camera at (0,0,0) looking toward -Z,
to world coordinates.  By default the camera is at (0,0,3) in world space
and the camera-to-world matrix is

	1  0  0  0
	0  1  0  0
	0  0  1  0
	0  0 -3  1

(Note that the matrix is written to be multiplied by a row-vector of
coordinates multiplied on the left.)

If you were looking at an unnormalized object lying in the range 0 .. 20
on each coordinate axis, you might position the camera to (10,10,60) with

	(xform-set  Camera  
		  1   0  0  0
		  0   1  0  0
		  0   0  1  0
		-10 -10 -60 1
	)

   Stuart