On Thu, 2 Oct 2008 18:31:16 -0400, the infamous "Ed Huntress"
scrawled the following:

You might be interested in a job I did with Rhino when I was at Wasino. We
were pitching Ford Motor on our lathes with the elliptical-machining gadget
for turning pistons in production. Car pistons today have complex shapes.
The Ford piston we were working on was a near-ellipse at the top, which
blended into a true ellipse near the middle, and then into another
near-ellipse at the skirt.

Ford gave us the formulas for the three shapes and I loaded them into Excel
so it would produce finite values at 36 points around the piston for each
formula. Then I loaded those values into Rhino as a script (Rhino will read
directly from Excel). Rhino blended the points with NURBS curves into a
smooth shape around the piston. And, the more interesting part to me, it
took the values of each of the three formulas at every 10-degree increment
and blended *them* from top to bottom of the piston. The end result was an
all-NURBS 3D shape.

The purpose of this was not to machine the pistons from those values, or
from the Rhino file (Ford gave us CAM files to machine the pistons), but
rather to make illustrations so we could show what we were doing.

Of course, the non-cylindrical values were a couple of thousandths here and
there, so you couldn't see it, either in the Rhino file or in a machined
piston. The reason I loaded it into Excel first was so that I could apply
multipliers to the values and play with them until I got something
exaggerated enough to see easily in the rendered Rhino file. It was
tricky -- too much and it distorted the shape beyond all recognition. But by
being able to just plug in new multipliers and then to see the rendered file
in less than a minute, I was able to adjust it by trial and error in around
15 minutes.

Ford was impressed by this and I think they adopted it for their own
purposes. Rhino handled it for us slick as could be.

Great story. Thanks for sharing it. (Watch Rhino ask to use it for
their testimonial page, eh?)

Gee, Ed. The way you crank those numbers around, it's surprising that
you never made it into _politics_. gd&wvvf


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If the gods had meant us to vote, they'd have given us candidates.
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