[osg-users] How to Convert Lookat to Projection and View Matrices

[Erik Hensens]

Thank you Sebastian!

The issue here is that the camera is not yet at the lookat in question. Basically, I have an eye, a center, and an up vector, and I need to be able to convert between 3D world coordinates and 2D screen pixel coordinates before the camera actually gets to the final lookat.

Is that possible?

I hope that all makes sense...


SMesserschmidt wrote:
> Am 22.09.2015 um 16:08 schrieb Erik Hensens:
> 
> > Thank you for the reply Glenn!
> > 
> > You say that the projection matrix doesn't depend on the lookat parameters; what does it depend on?
> > 
> The projection matrix depends on the size of your viewing frustum. 
> Usually near/far plane and the dimensions (angles) of the field of view.
> You can use the camera->get/setProjectionMatrix functions here.
> For instance:
> 
> viewer->getCamera()->setProjectionMatrixAsFrustum(
> aspect_x * near_plane * left_angle,
> aspect_x * near_plane *right_angle,
> aspect_y * near_plane * bottom_angle,
> aspect_y * near_plane * top_angle,
> near_plane,
> far_plane
> );
> 
> Cheers
> Sebastian
> 
> > 
> > Thanks in advance!
> > 
> > 
> > gwaldron wrote:
> > 
> > > You can make the view matrix:
> > > 
> > > osg::Matrix::lookAt(eye, center, up)
> > > 
> > > 
> > > This has nothing to do with the projection matrix though; that doesn't depend on your look vector.
> > > 
> > > Glenn Waldron
> > > 
> > > 
> > > 
> > > 
> > > On Tue, Sep 22, 2015 at 9:24 AM, Erik Hensens < ()> wrote:
> > > 
> > > 
> > > > Hi everyone!
> > > > 
> > > > How can I compute the view matrix and the projection matrix from a set of lookat parameters (eye, center, and up)?
> > > > 
> > > > I'm asking because I need to compute the MVPW for a given lookat before the camera is actually at that lookat.
> > > > 
> > > > I'm totally stumped and any help would be greatly appreciated!
> > > > 
> > > > Thank you!
> > > > 
> > > > Cheers,
> > > > Erik[/list]
> > > > 
> > > > ------------------
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> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
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