Dealing with Crossing Cases
The hard part of clipping is handling objects and primitives that straddle clipping planes.
In some cases we can ignore these problems because the combination of screen-space clipping
and outcode clipping will andle most cases. However, there is one case in general that cannot
be handled this way. This is the case when parts of a primitive lies both in front of and
behind the viewpoint. This complication is caused by our projection stage. It has the nasty
habit of mapping object in behind the viewpoint to positions in front of it.
(Click above to see projection)
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