[osg-users] setProjectionMatrix and FOV

Paul Martz pmartz at skew-matrix.com
Fri Mar 27 07:15:37 PDT 2009

You can either use a true orthographic projection, or you can set the
TrackballManipulator home position so that the viewpoint is further away. If
you are really trying to create a "near orthographic" (but not a true
orthographic) projection, then setting the eye distance very far away is the
right approach.

At my former employer, we used to set the FOV to about 10 degrees to mimic
the angle actually subtended by our render window on the screen. (10 degrees
is not as extreme as what you're doing, but it's still pretty extreme
compared to most 3D apps, and approaches orthographic.) But then we needed
to see an entire aircraft in that window, so we had to set the viewpoint
quite far away to get the entire aircraft into that 10 degree field. You'll
need to do the same.

Paul Martz
Skew Matrix Software LLC
+1 303 859 9466

-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Tomas
Sent: Friday, March 27, 2009 5:19 AM
To: OpenSceneGraph Users
Subject: [osg-users] setProjectionMatrix and FOV

Hello osg users,

I am trying to set the camera perspective projection to 'near' 
orthogonal. I achieve desired projection by setting the FOV to some low
number (1.0).
When the projection matrix is changed in this way, the scene is 'zoomed-in'.
This means, that MatrixManipulator::home does also zoom-in and the scene
does not fit to the view (using TrackBallManipulator).
It is clear what happens, but how can I prevent the 'zooming' in the best
way? I could apply some scaling factor to the MatrixManipulator, but this
seems to me not a clean solution...

many thanks,

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