Rock'n Unroll

Replies to This Discussion

Permalink Reply by David Rutten on February 24, 2010 at 3:10am

Hi Ivan,

unrolling is one of those operations that is only solved to within accuracy. Ok, cylinders are a special case and could be unrolled easily to a very high accuracy, but other surfaces cannot. If your document tolerance is 0.01, then 282.743 and 282.742 are the same number within tolerance.

Also note that if you increase the tolerance, all you'll get is more overlapping digits, the comparison will probably still be False. The chances of two floating point numbers being exactly identical if they are the result of two different operations are very small indeed. Almost all arithmetic operations in the computer carry some sort of fuzz in the least significant digits, and an Area computations contains a lot of arithmetic operations.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Chris Wilkins on February 24, 2010 at 6:34pm

Speaking of fuzz in digits, I'm not sure if that was to blame, but I was recently getting an error when intersecting 2 circles, and getting 4 results, instead of 2. Three of them were in nearly the same place. It was easy to work around, but I figured I'd mention it, since it seems sort of buggish.