How do I bend a square horizontal bar like in the picture?

Question

I want to bend a square bar with a hollow inside. What should I do to bend it into the shape as shown in the reference pictures?

If possible, I would like to know how the square bar bends in Blender using physics.

I'd like to make a video where the square bars are bent and crushed.

There are so many ways and approach to this : you can model it by hand, sclupt or even use physics or what not. What have you tried already? — mqbaka mqbaka, Aug 01 '23 at 04:33
I've just started blender, and I'm still researching how to do it on the web. — 黒瀬光彦, Aug 01 '23 at 04:42
If possible, I would like to know how the square bar bends on the blender using physics. — 黒瀬光彦, Aug 01 '23 at 04:45
I'd like to make a video where the square bars are bent and crushed — 黒瀬光彦, Aug 01 '23 at 04:47
Maybe this tutorial could lead you to the right direction https://www.youtube.com/watch?v=uzfhjgn1oVw&pp=ygUZYmxlbmRlciBzb2Z0IGJvZHkgcGh5c2ljcw%3D%3D ? — mqbaka mqbaka, Aug 01 '23 at 05:13

score 5 · Answer 1 · answered Aug 01 '23 at 08:38

Playing around with a cloth simulation, I managed to get that far:

Adding subdivisions before the cloth simulation will increase the foldiness, though that also depends on cloth resistances:

I started with the default cube, resized it on $z$ axis, ✲ CtrlR added loopcuts to make it roughly square-quads based again, but then decided to add much more loopcuts in the bending area:

Probably many of those sparse loopcuts away from bending can be removed, and the dense loopcuts shifted up, as I wrongly predicted where I'll bend…

The bending animation is done using this modifier stack:

bevel to add holding loops for Subdivision Surface
Subdivision Surface to give it the final base profile and geometry density
Simple Deform to bend by 90°
The magic of cloth sim
Smooth the bends so faces don't overlap on themselves
Another Subdivision Surface to further smooth the output by adding vertices

Proper Weight Painting is crucial, and so by improving it you will get better results than me:

Cloth settings are extremely important as well, but I left most settings to defaults and just pinned the weights from above and added just a touch of pressure from inside to direct the bends outside:

What a beauty! I wonder whether a blurred GN-generated tension-map would stand any chance of doing your weight-painting for you. — Robin Betts, Aug 01 '23 at 09:45
@RobinBetts nice idea, I was thinking of something similar: after first pass, convert it to shape keys, then weight-paint the areas based on how much you want them to change. Could even weight-paint individual frames differently using this, then replay simulation, rinse, repeat until happy with the result… — Markus von Broady, Aug 01 '23 at 10:28

How do I bend a square horizontal bar like in the picture?

1 Answers1