Create 2D cutout of 3D object using geometry nodes

Question

Create 2D cutout of 3D object using geometry nodes.

I'm trying to create a 2D cutout from a geometry node generated 3D cone (and make it procedural)

See red arrow pointing to 2D image that I'm trying to create and make 3D printed using very thin layers (which will be bendable)

My thoughts were to use geometry nodes to have people customize their own cone dimensions and have the 2D cutout be generated.

Example / My thoughts:

2D cutout generated from the Arc node (so it can be 3D printed by extruding in Z direction for depth)

I'm having some trouble with the math conversions and what the correct start/sweep angles should be

quellenform · Accepted Answer · 2022-08-05 10:45:19Z

3

The following setup should do exactly what you want:

Theses are our base values:

Height of the cylinder = $h$
Radius of the circle = $r_1$

The formulas for this are:

Arc Length (the circumference of the circle): $b = 2 * r_1 * \pi$
Radius of the arc: $r_2 = \sqrt{r_1² + h²}$
Arc angle: $\alpha = \frac{b}{r_2} $

answered Aug 4, 2022 at 22:27

quellenform♦

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2

$\begingroup$ Hi @q! Maybe misinterpreting the brief, apologies if so, (I make myself available to be stomped all over.. :D ) ..but don't we need a bit of Pythagoras here? The arc-radius of a cone base-radius 1, height 2, is sqrt(5), not 3. $\endgroup$
– Robin Betts ♦
Commented Aug 5, 2022 at 7:25
1

$\begingroup$ @RobinBetts Haha, Yes, you are absolutely right. It was already very late yesterday and while shortening the nodes, I probably swept some important things of our friend Pythagoras under the carpet. :D ...I'll correct this unforgivable mistake shortly.... $\endgroup$
– quellenform ♦
Commented Aug 5, 2022 at 8:49
2

$\begingroup$ @RobinBetts The answer has been corrected. Thanks for reading carefully and for pointing out the error instead of downvoting right away! I will be more careful in the future when shortening the nodes down ;-) $\endgroup$
– quellenform ♦
Commented Aug 5, 2022 at 9:51
1

$\begingroup$ I would never downvote without an explanation, and before attempting a resolution, unless a blatant abuse. I was in a hurry, too. You got my +1 before I looked at the nodes and thought: 'hang on a minute...' :) $\endgroup$
– Robin Betts ♦
Commented Aug 5, 2022 at 10:33

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