Re: [Plib-users] sgFrustum setting to the same as opengl

[Steve B. <sjb...@ai...>]

Oliver Batchelor wrote:
> 
> I have a function for setting up a view frustum  I want to know if
> its getting the right values to be setup the same as the opengl one
> ...
> I am getting some wierd results in my landscape renderer -
> If I roll around etc everything dissapears  but I cant see whats
> going wrong ...
> 
> here is the setup code ...
> 
> void View::Set(float angle, float near, float far) {
>     glMatrixMode(GL_PROJECTION);
>     glLoadIdentity();                           // Reset The Projection Matrix
> 
>     gluPerspective(angle, 640.0/480.0, near, far);      // Calculate The Aspect Ratio Of The Window
>     glMatrixMode(GL_MODELVIEW);
> 
>     frustum.setFOV(angle, angle) ;
                     ^^^^^^^^^^^^
               That's going to set the HFOV and VFOV to the
               same values - but you (seem to) have a 640x480
               window.  Try using  (angle,-1) - and we'll compute
               the second angle for you assuming a 3:4 aspect
               ratio.

Dunno if that's enough to account for your wierdness.

You could also use a sgFrustum::getMat4 to grab the matrix out
of the sgFrustum - then you can use glLoadMatrix to put it
onto the projection stack - no messing with gluPerspective - and
it guarantees a good match.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
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