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I have a bunch of 2 polygon objects, each with a fold between 2 vertices. I need to figure out the angle of the bend and then "Unfold" into a flat plane without distorting the dims of the two polygons. These will be exported as 2D for waterjet cutting.

Picture is an example of the objects.

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    $\begingroup$ Note: when designing for CNC production and you're flattening sheet material, keep in mind that the bend itself (bend radius) also "consumes" material and might cause dimensioning problems. Blender does not account for this, especially in a 2D fold along a single edge. $\endgroup$
    – asoftbird
    Jan 26, 2020 at 15:49
  • $\begingroup$ blender.stackexchange.com/questions/165654/… $\endgroup$
    – batFINGER
    Oct 16, 2021 at 8:38

1 Answer 1

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This is a fun question, so let me show my limited knowledge :).

1) Edge angle
You can display the angle of the bend by enabling Edge Angle in the Overlay menu.
It's only visible in Edit Mode, and you have to have the edge selected.

enter image description here

2) Unfolding into 2D
Very fast and very dirty way for the unfolding bit:
If you unwrap your mesh with Smart UV project, you will get it unfolded as a UV map.
If you do it right, it will perfectly correspond to the shape of the faces.
You can then export it as a .png,.svg or eps.

Unwrap your mesh with Smart UV project enter image description here

Export your UV map as svg. enter image description here

Note:
This is definitely a "solution".
But maybe the Blender Elders will banish me to hell for this.

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  • $\begingroup$ Thanks! I'll give it a try. When I unwrapped UV previously, it split into islands. This is my first go in blender, so I wasnt sure how to fix. I enabled the paper models export, exported as svg and sort of did the same thing, but I'm not sure the scale is correct (To start) so now I'm going back and double checking. Had no idea on the edge angle though, that's awesome! Will it matter how the object is aligned in relation to the axis? $\endgroup$
    – Chad
    Dec 2, 2019 at 22:30
  • $\begingroup$ The alignment of the object plays no role in edge angle - I tested it. It shows exactly the angle between those two faces. Make sure you have your object scale applied in Object->Apply->Scale, because that can mess up your UV map scale. $\endgroup$
    – jachym michal
    Dec 2, 2019 at 22:34
  • $\begingroup$ Thank you so much! Quick scale question, because I'm sure it's me. When I'm import scan data, that is scaled (Either obj or stl) does it stay scaled? Did I screw it up somewhere? My object that should be about 1250 mm is about 1,250,000 mm $\endgroup$
    – Chad
    Dec 2, 2019 at 22:43
  • $\begingroup$ It's not your fault. When importing .obj and .stl, the scale is often screwed up. It's because each software has different units :). You just have to scale it manually. $\endgroup$
    – jachym michal
    Dec 2, 2019 at 22:50
  • $\begingroup$ That's a bummer. I generally stay in mm in all of my software I just wasn't sure if there was a scale factor that could be applied to the "original scale".....so i was thinking i had messed with the scale transforms, and resetting to 1 would take me back to original scale......no such luck! Thanks again! $\endgroup$
    – Chad
    Dec 2, 2019 at 23:03

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