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Hidden Surface Removal
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Hidden Surface Removal
Backface Culling
Backface Culling
A simple way to perform hidden surface is to remove all ``backfacing'' polygons.
The observation is that if polygon normal is facing away from the viewer then it is ``backfacing.''
For solid objects, this means the polygon will not be seen by the viewer.
\
Thus, if
, then cull polygon.
Note that
V
is vector from eye to point on polygon
You cannot use the view direction for this.
Backface Culling
Not a complete solution
If objects not convex, need to do more work.
If polygons two sided (i.e., they do not enclose a volume) then we can't use it.
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A HUGE speed advantage if we can use it since the test is cheap and we expect at least half the polygons will be discarded.
Usually performed in conjunction with a more complete hidden surface algorithm.
Easy to integrate into hardware (and usually improves performance by a factor of 2).
CS488/688: Introduction to Interactive Computer Graphics
University of Waterloo
Computer Graphics Lab
cs488@cgl.uwaterloo.ca