Length
Specified the length of the smear in cm.
Samples
As the mear length increase, it may be necessary to increase
the number of samples to reduce the sampling aliasing artifacts
which shows as repeating textures in the smears.
Note that the processing time increase proportionally with the
number of samples.
Gain
As the number of samples increase, the values coming from the
function tend to average toward 50%. It may be necessary to increase
the gain in order to rregain better contrast.
Axis
This is the axis vector along which the smearing is aligned.