Re: FOV Acquisition

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Jim Helman (jimh++at++surreal)
Sat, 13 Nov 93 01:36:02 -0800

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> While running Performer (or anything on top of GL) I need to
> acquire the FOV in both x and y. GL does not provide a FOV query,
> however, by directly reading the projection matrix (perspective) I
> can get the FOV's. Is there any problem to getting this info while
> running Performer?

In the *draw* process callback, you can use something like:

        prev=getmmode();
        mmode(MPROJECTION);
        getmatrix(mine);
        mmode(prev);

to get the projection matrix. You can then use the matrix
definitions in the GL Programming guide to back out the FOV, but the
form of "mine" that Performer uses is not documented, it could have
other transformations built in, and it could vary between releases.

rgds,

-jim helman

jimh++at++surreal.asd.sgi.com
415/390-1151

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