z buffer=?

[red_Marvin]

In the allegro examples there's an example of a tethraedon
and a cube rotating so they are colliding, but the polygons
are drawed correctly and it should have something with z buffering
to do... Can somebody explain z buffering to me?

[Magos]

When drawing stuff in 3D space, you don't want an object which is behind another object to be drawn in front even if it is rendered last.
Therfore, a Z-buffer stores the Z coordinate for every pixel. When a new pixel is about to be drawn, it checks the Z-buffer if it's own Z-coordinate is in front of the Z-coordinate stored in the buffer. If not, it won't draw.