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Units and rounding: downsides of excessive precision?


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17 hours ago, line-weight said:

Of course many of us have plenty of experience of working with builders who have no intention of looking in detail at the drawings anyway!

That brought a smile to me and an old memory of a renovation to public recreation facility where a former general contractor become construction management convinced the city that they could oversee the trades' contracts on the city's behalf and save them from some professional service fees and general contractor markup. But the guys continued to operate like a general contractors only without usual financial restrictions and contractual obligations in a tendered service contract. We were supposed to sign off that the product they were about to receive achieved our documentation's design intent. The list of errors that they allowed the contractors without repairs or penalties was a doozie due to the lack of attention to viewing the document details. A gap beside an automatic door frame and the adjacent wall assembly that you could clearly see the objects outside, fiberglass insulation laid on plastic film in the ceiling of a tiled steam room where foil faced rigid foam was to have been carried up and over from the walls, shower floors with no slope to the drains, non-structural steel framing in a ceiling assembly that called for pressure treated wood due to high humidity levels. They had one contractor install a water slide through the building envelope before they figured out there was flexible gasket sealing system and a different contractor was required to prepare it beforehand.

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  • 1 month later...

Hi all, the discussion here is mostly dimensions being (too) accurate, but what if I want to have a @line-weight (pun intended) with more than 2 decimals? We have laser cutters here that DEMAND us to provide line thicknesses of EXACTLY 0,025mm. If I try this in VW it always ends up in 0,03mm - which is no good for the machine. Of course I can go back to using autocad or illustrator, but hey...

 

Hope there is some hidden feature to automagically add that third digit to lines!

 

Regards, JB

HMC_LAB laser 600x300mm.vwx

Edited by Jan-Burger TROOST
adding file
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3 hours ago, Jan-Burger TROOST said:

Hi all, the discussion here is mostly dimensions being (too) accurate, but what if I want to have a @line-weight (pun intended) with more than 2 decimals? We have laser cutters here that DEMAND us to provide line thicknesses of EXACTLY 0,025mm. If I try this in VW it always ends up in 0,03mm - which is no good for the machine. Of course I can go back to using autocad or illustrator, but hey...

 

Hope there is some hidden feature to automagically add that third digit to lines!

 

Regards, JB

HMC_LAB laser 600x300mm.vwx 66.97 kB · 2 downloads

....maybe you have to set your units to microns and scale all your drawings up x1000?

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I'm interested in what the effect is in the laser cutter. Can't you just map a color/class name to a kerf in the cutter software?

 

AFAIK

If you enter 0.025mm for the Line Thickness that's what you'll get and you can dismiss the rounding in the dialogue window.

You can enter 0.02 for example. The minimum seems to be somewhere in the neighbourhood of 0.0127mm

Changing the Drawing Units won't affect the range of Line Weights that are available.

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28 minutes ago, bcd said:

I'm interested in what the effect is in the laser cutter. Can't you just map a color/class name to a kerf in the cutter software?

 

AFAIK

If you enter 0.025mm for the Line Thickness that's what you'll get and you can dismiss the rounding in the dialogue window.

You can enter 0.02 for example. The minimum seems to be somewhere in the neighbourhood of 0.0127mm

Changing the Drawing Units won't affect the range of Line Weights that are available.

Thanks, that’s what we do already: red 255/0/0 is cutting through, green 0/255/0 is rasterizing and blue 0/0/255 is engraving. But all lines need to be 0,025mm exactly. I tried what you suggested & entered 0,025 which was rounded to 0,03. Still the laser won’t accept it…

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From working on scripting in VW and having to use feet and inches for daily drawing (talk about rounding problems) I believe that internally VW uses mm out to something like 14 decimals for linear dimensions.

 

If you think about high school geometry it can't always be exact.  Draw a square exactly 1000mm on each side.  Draw the diagonal.  The length of the diagonal will never be expressible as a rational number in mm, even though its endpoints can be exactly expressed in mm coordinates.  Same with the circumference of a 1000mm diameter circle.  So what you get is a multiple of pi or the square root of 2 out to 14 (or whatever) decimal places.  

 

So in that case and probably many others, the dimension is always rounded.  You just have to decide how many decimal places you need to see.

 

If you type in a length or a coordinate into the OIP, I believe it will set it to be exactly that (with trailing 0s out to 14 (or whatever) decimals no matter what the unit precision preference is, but show up as a rounded value if your precision preference is set lower. 

 

Circles are different.  I think they are calculated as 256 line segments, but then something magic happens and it smooths it out for the display.  If you zoom way in on a circle you can see the segments while you are zooming, but then they disappear when you stop zooming.

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18 minutes ago, michaelk said:

 

Circles are different.  I think they are calculated as 256 line segments, but then something magic happens and it smooths it out for the display.  If you zoom way in on a circle you can see the segments while you are zooming, but then they disappear when you stop zooming.

 

Unfortunately, no such magic happens when viewed in OpenGL or rendered in renderworks, which can cause all sorts of problems with gradual curves.

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7 minutes ago, line-weight said:

 

Unfortunately, no such magic happens when viewed in OpenGL or rendered in renderworks, which can cause all sorts of problems with gradual curves.

Segments in OpenGL renders have to do with its prefs and segmentation quality, right? It’s not the source object that converts it to a 64 segments circle. If you select it rendered, that orange line will show the original object. 

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