[discarded] User accessible settings for modelling precision

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Ulicad
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Re: [solved] User accessible settings for modelling precision

Post by Ulicad »

My apologies to all.
The outright deletion of the original text was a mishap and I could not succed in restoring it again. Can't find the original text and the trash bin is deleted - it's so clean everywhere... :?
chrisb wrote: Wed Mar 22, 2023 5:13 pm ... A native speaker may enlighten us about the accurat definitions of accuracy, precision, ... in this context. ...
This would be great! And a 'doctoral thesis' wouldn't be required..
Regards, Ulicad / Uli
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jimb
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Re: [solved] User accessible settings for modelling precision

Post by jimb »

Besides I'm not sure if the connection between "accuracy" and the number of decimals is very accurate, which may be due to our language barrier. A native speaker may enlighten us about the accurat definitions of accuracy, precision, ... in this context.
In general accuracy denotes correctness. You can think of precision is roughly how many digits (not counting leading and trailing zeros).

Examples:
Accurate but not precise: Speed of light is 300,000,000 m/s
Precise but not accurate: Speed of light is 345,678,900 m/s
Accurate and precise: Speed of light is 299,792,458 m/s (actual value in a vacuum)
Ulicad
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Re: Only partial "Shape View" settings?

Post by Ulicad »

adrianinsaval wrote: Wed Mar 22, 2023 1:25 pm
Ulicad wrote: Tue Mar 21, 2023 6:56 pm ... Since the no. of decimals used in processing is influencing the time required to execute a command ...
No the processing time is not affected by this setting, this is only the number of decimals used to round parameters for user convenience ...
adrianinsaval wrote: Wed Mar 22, 2023 1:25 pm ... this setting [Remark: Tesselation] does influence processing time as it relates to meshing of the shape for display ...
Thanks a lot for both infos! I was chewing a bit on the no. of decimals user-settable but probably I have swallowed it..

Regards
Uli
Regards, Ulicad / Uli
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chrisb
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Re: [solved] User accessible settings for modelling precision

Post by chrisb »

jimb wrote: Wed Mar 22, 2023 9:57 pm Accurate and precise: Speed of light is 299,792,458 m/s (actual value in a vacuum)
Thanks! I'm glad FreeCAD doesn't use a lightyear as its basic unit :lol: .
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Ulicad
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Re: [solved] User accessible settings for modelling precision

Post by Ulicad »

jimb wrote: Wed Mar 22, 2023 9:57 pm ...
In general accuracy denotes correctness. You can think of precision is roughly how many digits (not counting leading and trailing zeros).

Examples:
...
Precise but not accurate: Speed of light is 345,678,900 m/s
...
Thank you!
In the context of your contribution, the Topic requires reviewing. It is marked as [draft] now.

Regarding your samples: I could not follow your 2nd example fully.
Why would you say this is not aaccurate? Is it because the additional information 'Vacccum' is not given?

Regards
Uli
Regards, Ulicad / Uli
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jimb
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Re: [draft] User accessible settings for modelling precision

Post by jimb »

Regarding your samples: I could not follow your 2nd example fully.
Why would you say this is not aaccurate? Is it because the additional information 'Vacccum' is not given?
I only added the "actual value in a vacuum" to the one example as that is the correct value by definition. Just assume they were all meant to be speed of light in a vacuum. The point about the 2nd example not being accurate, might be clearer if I said it is less accurate than the prior (or 3rd) one. Also all the (made up) non-0 digits imply high precision that is add odds with how far away it is from the correct value (about 15% error). Example 1 is only off by about 0.07%.
rdinohio
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Re: [draft] User accessible settings for modelling precision

Post by rdinohio »

Another way to look at it:
Precision is the spacing of the marks on your ruler or whatever you are measuring with. Accuracy is how close you get to the desired mark in the actual work.
Ulicad
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Re: User accessible settings of modelling precision?

Post by Ulicad »

chrisb wrote: Tue Mar 21, 2023 7:27 pm ...
Expert settings for Sketcher:
Preferences->Sketcher->General->TaskPanelWidgets->Show Advanced...
Hello Chris,
intending to finish this thread in a way that perhaps other users could benefit and additionally search engines more easily can find it, I'd like to have some more info or confirmation(s) if possible.

After looking at the advanced expert settings you mentioned, I can't see they would influence the precision in question - do I see this correctly? Precision in the meaning clarified by jimb here.

To recall and phrased somewhat more concise:
To be controlled is the precision of the CAD-model not only visible by the user but, far more importantly, as seen by other machines.

Machines for instance like 3-d printers, laser cutters, CNC machines and so forth.
Hereby assuming these machines are completely 'dumb' without any postprocessing on the shapes of the 3-D model in production. Since such machines can be different in their interpretation of the CAD-Model, the 'dumb' assumption is made to be 'on the safe side' for a user.

For comprehension:
Intendedly or not, one result could be: a perfectly round cylinder by design has been machined with a number of plane surfaces instead of a smooth round surface. The same could happen with fillets for instance. (More I can't think of in the moment.)

Are there more controls existing in FC than 'Maximum deviation ...' and 'Maximum angular ...' in the tesselation settings available?

If yes, these need to be added, if no, the context is clear for finalyzing the thread.

Hope you find the time, regards
Uli
Regards, Ulicad / Uli
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chrisb
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Re: User accessible settings of modelling precision?

Post by chrisb »

Ulicad wrote: Wed Nov 15, 2023 3:23 pm For comprehension:
Intendedly or not, one result could be: a perfectly round cylinder by design has been machined with a number of plane surfaces instead of a smooth round surface. The same could happen with fillets for instance. (More I can't think of in the moment.)
In FreeCAD a cylinder is perfectly round. What is subject to precision issues is the placement, the radius, the representation on the screen.
When dealing with other applications it depends heavily on the exchange format what you get. Exporting to stl will always be subject to heavy tesselation.
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Ulicad
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Re: User accessible settings of modelling precision?

Post by Ulicad »

chrisb wrote: Wed Nov 15, 2023 4:45 pm ... What is subject to precision issues is the placement, the radius, the representation on the screen.
When dealing with other applications it depends heavily on the exchange format what you get. Exporting to stl will always be subject to heavy tesselation.
To become clear on this issue, I am considering FC as a source only, without considering interfaces of other appllications.

Having this restriction, how could the precisions of " ... the placement, the radius, ..." in the FC-model be controlled? By other or additional settings than already mentioned?
Regards, Ulicad / Uli
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