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polsim - parabolarising


 

from this doc, 18th Century mirror making, short strokes with a small amount of overhang to parabolize the mirror.

Simulation:

full size tool 460, stroke 60, x offset 140 

but from stellafane, the parabolizing stroke is "w center" stroke

which is a combination of these 2 strokes( chordal short stroke+ CoC 3/4D stroke)

s 60, y 110

s345, y 0:



from bbastro,

if sphere is a flat surface:



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