Subject:
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Re: number notation in official parts
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Newsgroups:
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lugnet.cad.dev
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Date:
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Thu, 11 Mar 2010 08:42:06 GMT
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Viewed:
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22674 times
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> My suggestion would be to read numbers in that notation but never write them.
I mostly agree with this policy.
> I'm not sure why LDDP would write them that way (it would require some strange
> output routines) but if one thing writes them then it's best to read them.
There is nothing strange in the routines, it is the standard format used to
represent very large or very small numbers in a limited number of digits.
Actually since values never get very large in LDraw parts (biggest is probably
50x50 baseplate, thus 1000 ldu), it's all a matter of proper rounding. As far as
I can tell, 4 digits after comma is OK for position coordinates, and 6 digits is
enough for matrices coefficients. The problem mentionned with values such as
1e-15 should not have occured if I had properly rounded the file.
Note also that LDDP has an auto rounding feature (on by default) that would have
prevented the problem from the beginning. But I disable it since this may
accumulate errors during complex parts work.
Also note that MLCad also cherfully generates scientific notation numbers (eg.
9.9e-005) for any number below 0.0001
Philo
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Message has 1 Reply:
 | | Re: number notation in official parts
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| (...) I definitely know this. I see them far too much in my job as a numerical physicist ;) My point is that to write in mixed format (some %f and others %e) requires some strange coding unless there is a weird language which does it automatically. (...) (14 years ago, 12-Mar-10, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: number notation in official parts
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| (...) My suggestion would be to read numbers in that notation but never write them. I'm not sure why LDDP would write them that way (it would require some strange output routines) but if one thing writes them then it's best to read them. Tim (14 years ago, 11-Mar-10, to lugnet.cad.dev)
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