Howard Trickey
49aa701645
Parameter controls concavity / convexity.
<.25 means: concave inward
.25 means: straight slanted
>.25 means: concave outward
.5 means: circular (the default)
1 means: straight along original sides
For now, there is a hard lower limit of .15
because more work is needed to get decent
results in the range below that.
The profile is actually a superellipse, and the
parameter is 1/4 of the exponent in the implicit equation
for a superellipse, except at the extreme values of 0 and 1.