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I'm working on a project and I have a video shot where I would like to drop a cloth sheet through the top of a building - Well, it's not exactly a sheet, it's a banner, but that is the idea.

enter image description here

At the start of the animation, I would like the banner to be "rolled" or something (not deployed), then that it deploys itself using gravity. There should be pins at the top (to fix it) and a weight at the bottom (so the banner doesn't "fly" to much).

enter image description here

I started to work on it: I have the cloth, I have 3 vertex groups (topPins, bottomPins, allPins), the topPins are attached to the top cylinder and the bottomPins to the bottom cylinder; which has rigid body enabled.

But I guess there is other things to do since... It doesn't work : the bottom cylinder keeps falling - and instead it should remains attached to the cloth, depending of its physic resistance/elasticity, I guess.

enter image description here

Also, I don't know how to handle the start situation.

Could someone help with some advices ? Here's the .blend file if you want to check.

If this is too complex, I think i'll end up with a simplier idea (just wind on the deployed banner)

Thanks a lot !

I found out this on Youtube. It looks like a great idea (roll the cloth curtain before unrolling it).

Tutorial for Blender - Curtain Call - Rolling up Material

I had several attemps but cannot reproduce its setup; maybe because of the Blender version ?

My actual .blend here if anyone wants to try...

gordie
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2 Answers2

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Here is another way to go. Instead of using pinning to connect the bottom vertices of the banner to the bottom cylinder, parent the bottom cylinder to the bottom 3 vertices of the banner. (Keep the pinning to the top cylinder so the top of the banner stays put.) That way, as the bottom of the cloth naturally falls due to gravity, the cylinder will fall with it. You would need to adjust the mesh of the banner to a staring position where the bottom vertices are near the top ones, and probably "bunch up" the rest of the flag so it's all up at or near the top.

Here is a quick and dirty implementation of that idea:

enter image description here

risingfall
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  • This seems cool, but will the cloth be affected by the weight of the bottom cylinder ? – gordie Sep 14 '18 at 23:50
  • No, I'm sorry to say it will not (if that's the desired effect). I am honestly not sure if there is a way to do a two-way connection between cloth and a rigid physics object (in that the rigid object's movement deforms the cloth, but the cloth modifies the movement of the rigid object by tethering it.) If a guru here knows how to do that I'd be very interested, my experiments in that regard failed. – risingfall Sep 14 '18 at 23:54
  • Or maybe should I work with vertex weights ? – gordie Sep 15 '18 at 08:32
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You need to stop the fall of the bottom cylinder at some point.

Using the animation keys, make the bottom cylinder falls from position A, banner rolled up at the top, to position B, banner fully deployed. Once it's at position B, make it not affected by gravity anymore, so that it remains in place and your banner remains fully deployed.

As for making the banner unroll, you could use a curve on the banner object, make it tightly rolled like a spiral, then animate the curve to make it go from a tight spiral to a straight line as the bottom cylinder falls, which would effectively look like the banner is unrolling from the top.

Sava
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