Re: [Gzz] PEG 1013: Add clipping state to vob scenes

[Tuomas Lukka]

> 
> - How deep a stack is allowed / required? This makes a lot of difference
>   for the OpenGL implementation which has native stacks of fixed depth.
> 
>    RESOLVED: Ultimately, stacks should be arbitrarily deep, with GL
>    switching to a different implementation method when the native
>    stack depth is exceeded. For now, it's acceptable to throw an
>    exception if the native stack depth is exceeded. If we run into
>    real-life problems with this, that'll be a good time to switch to
>    a more advanced system.
> 
> - Should clipping with this method work with nonlinear coordinate systems?
>   This is a very fundamental issue for OpenGL, since if the answer is no,
>   we can use clip planes and get rid of much unwanted geometry, getting
>   better performance; otherwise, we need to use stencil and draw 
> everything.
> 
>    RESOLVED: This method should work with nonlinear coordinate systems.
>    This ensures that we can use nonlinear coordinate systems for all
>    things we draw in OpenGL. For example, we can put a window into
>    a fisheye view without getting problems with clipping used on
>    that window.
> 
>    This method should be safe to use as the general case; it is
>    optimizations that should be the special case, used if necessary.

Actually, this gets really hairy now: if they need to be implemented 
using stencils, we'll need some sort of stencil reserving system
and there you can have 8 viewports nested, MAX. Might be possible
to kludge to have more, but...

        Tuomas