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Author Topic: Can I bend a sheet of paper with skinning?  (Read 1520 times)

AlecJames

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Can I bend a sheet of paper with skinning?
« on: May 09, 2012, 08:09:31 pm »

I'm trying to bend a sheet of paper around a tube.

Ive tried creating a cube x=180  y=85 y=1, x has one division, y has 32, z has 1 (I only want the paper to bend around y), convert to mesh, create a figure with root + bone (50 long) + bone (50 long) and skin it with the sheet.  Problem is I cannot get it the sheet to bend at the bone + bone junction. 

I think its because the influence of the skinning does not extend to the x edges (width) of the sheet.  If I extend the influence so it spans the x dimension, it also expands in the y direction so the influencing bone just rotates the paper instead of bending it.

Ive tried adding x divisions and it folds a V shape into the top middle of the sheet.

Ive tried to disable the y and z while expanding the influence region but the region still expands along all axis.

Any ideas on how I can bend my sheet along its middle?

(Long term I want to have 10 bones in a line so I can bend my sheet around a long tube.  I then want to animate it folding around the tube using as many key frames as required.  The only other way I can think of achieving this is to use morph targets but I've tried this before and wasn't very pleased with the result.  I think a multibone figure will give a better result - maybe I need a 2 dimensional array of bones?)   

Thanks for any suggestions
A
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davdud101

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Re: Can I bend a sheet of paper with skinning?
« Reply #1 on: May 10, 2012, 01:08:30 am »

I think you're problem is that you don't have enough divisions (you'll need, I'd say at least eight, because it bends around the divisions.) then you'd want  to have a nice fade between the two (or however many) bones skins to ensure a good skinning. Hopefully that's what you were wondering, and if not, care to explain a bit more?
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Raxx

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Re: Can I bend a sheet of paper with skinning?
« Reply #2 on: May 10, 2012, 02:25:44 am »

You're talking about bone influences. For this kind of thing you need to assign the vertices manually using painted weights.

Morphs are also a great way to handle paper-like deformations, but it'd take a bit of tinkering to get it to wrap around an object perfectly with the vertices moving in the right direction at the right time, as you might have already experienced.
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AlecJames

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Re: Can I bend a sheet of paper with skinning?
« Reply #3 on: May 10, 2012, 07:10:13 pm »

Thanks for the feedback

I've never tied painted weights before - thanks Raxx for suggesting it, looks like this could be the answer

I've attached a picture to illustrate what I'm asking (sorry should have done this first)

A = what I want to achieve (but using a bone to make the fold so it's easy to animate multiple folds)
B = a simple fold using the weights technique
C = first attempt, simple bone influences (8 x 20 mesh)
D = bone influences using the upper two horizontal bones

I'll work on weights with more bones - I think this will do what I want.

Thanks again for the comments
A
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davdud101

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Re: Can I bend a sheet of paper with skinning?
« Reply #4 on: May 10, 2012, 10:45:47 pm »

From the looks of it, you only painted a small section of it (unless you're using bone influences, in which case, switch over to weights.). You'll have to paint that entire top row of vertices so that that one bone controls all those vertices.
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