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After an uninformative pixel test, where
subpixel testing may be performed.
If
then we set to ,
since
The sample is commonly chosen to be a corner
of .
We may refer to this method as subpixel sample testing,
to distinguish it from the other forms of subpixel testing,
which are presented later.
Compare the following two renderings
of , produced using, and not using, subpixel testing:
denotes a rendering produced using subpixel
sample testing; all subpixel rendering methods
work in conjunction with pixel testing.
Of course, renderings produced using subpixel testing depend on which
portion of the subpixel was chosen to test.
The rendering depicted is optimistic; for every
pixel on the boundary, a sample within
the graph was chosen.
Consider rendering ; here
are two renderings,
produced using, and not using, subpixel testing:
The rendering using subpixel testing was fortuitous,
since the sample chosen from each dark grey pixel
lay within the graph.
Later methods will prove to be more reliable
in rendering such graphs.
Next: 4.2.5 Exhaustive Subpixel Testing
Up: 4.2 Basic Rendering
Previous: 4.2.3 Pixel Testing