Re: [AD] Patch for the documentation of polygon_z_normal()

[Andrei Ellman <ae-a-alleg@xxxxxxxxxx>]

Robert Ohannessian wrote:
> > That's probably too difficult for a beginners guide. You can't just do
> > camera->poly dot normal > 0 and have that work, you need to compare
> > against a range of values (which can be negative), based on the
> > projection transform, and clip against that.
>
>
> Now that I think about it, this can't work either. You need to have your
> geometry in screen-space.


If it's too complicated for the allegro docs, perhaps it should go in 
one of the examples.

So what would be a good method for back-face culling without first 
converting into screen space? The advantage this has is that it saves a 
persp_project() call for any vertices who'se polys are completely obscured.

If we can come up with a solution that we all can agree on, I'd 
recommend we update exscn3d.exe to use it as it uses more vertices than 
the other examples, and it uses 3D clipping as well.


AE.