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Kinematics
11-29-2010, 01:29 PM
I have a shot and this isn't exactly the main element, but I am extremely disappointed with the fact that I couldn't even handle this. I would love some help.

It is the typical gift wrapping look. square cube box. a ribbon coming up each side to form a nice lil bow on top.

http://www.charlesandhudson.com/archives/christmas-gift.jpg

How do I go about rigging this so that I could do a simple untie that looks good, it doesn't need to be amazing, afterall it is magically untying itself?

I tried to have the bow untie itself and point constraint the ribbon bits on the side, and turn it off as the bow ends gets pulled out to the sides allowing ncloth to completely take over. I wasn't successful at all.

I tried spline IK but shaping the bow was hard enough, let alone drawing bones along the curve and trying to untie it using clusters.

I was thinking if I could somehow using this method or something like that till it has been untied and then have nCloth take over.

I've read up on deformers and dynamics but still can't seem to mix the tools up together nicely. They tend to not work with each other or give me more trouble some other way. Do let me know if you guys have any advice. Please be as detailed as possible, it would be extremely helpful.

Thank you so much guys. =)

vancliff
11-29-2010, 01:57 PM
I tried to do something like this like 6 months ago and it was utterly impossible. The animation consisted of a ribbon of flags traveling and at the end making a knot. Posted the same question and never received an answer. Later i found the way to do it, I animated the ribbon but the knot i did it with blendshapes cleverly appearing in the final keyframes.

HowardM
11-30-2010, 12:14 AM
hmmm, this would be a little tricky but if you have time it probably could be done with nCloth.
so, how much time ya got? ;)

quick test, in about an hour - http://vimeo.com/17311859

animatedfox
11-30-2010, 03:21 AM
We did this commercial at work (Framestore NY):
http://multivu.prnewswire.com/mnr/ultimaterewards/44980/
Did a lot of Dev on tying/untying in a directable way.
Ended up using a rig that was basically a long curve with a bunch of cluster controls broken down into groups of Course control and Fine control. No joints were used.
Some offset curves for a good up-vector was essential.
Then we lofted a nurbs surface along the curve, converted to polys and extruded to add thickness after a nCloth dynamics pass.
To get the pinching/scrunching we added controls all along the ribbon as well.
This got us a long way towards where we wanted to be but we couldn't get the center of the bow tight enough or direct the finished ribbon enough...so after trying a few more things we ended up adding a lattice rig with a simply rigged lattice for each part of the bow as well as the center knot.
nCloth was added in the end to remove any penetration and add little bit of extra movement.
A good bit of wrinkle/bend movement was faked with animated bump maps as well.

We tried nCloth at different steps and got some okay results...but we had more animators than cloth TDs on the job so we needed something they could animate and change quickly, so cloth just wasn't practical.

The animation in the shot of the ribbon tying around the shoe ended up being easy to reuse for any other tying animations with little tweaks.

BUT you need to UN-tie...well we needed to un-tie in the next spot. (couldn't find it online) Ended up being able to reverse the original shoe animation and make a few tweaks and it worked like a charm.

The big reveal is that the finished shoe animation took 2 weeks once the kinks had been worked out of the rig (about 80 frames)...all in all that tying animation really took 4 weeks with rig testing re-working and re-animating.

Good luck!

Kinematics
11-30-2010, 06:12 AM
Hey guys,

Thank you for the tips. I definitely need to read up more on nclothes to understand how to mix that with the hand animated curves/mesh. Man.

@animatedfox

The quality of the animation was really beautiful. Thank you very much for sharing the time it takes. It is kinda nice to know something like that takes 2-4weeks. We are a pretty small shop so sometimes we just have no idea if it is the lack of skill sets or when to consider it "to difficult" and try other methods. Plus, my clients would look at me funny if I budgeted for that kinda duration.

Also, thanks for the tips. I'll look into those specific items you mentioned and try to work something out from that. I am trying to understand how to animate a mesh and then run an ncoth simulation over it to prevent intersections.

@HowardM

Hey Howard, thanks for taking the time to do a little test. It looks like I would take quite a while to get it to the quality I need though the concept seems generally good. But I suppose it is controlled with constraints which makes directing it a little difficult. some of the movements of a tie-ing knot would require the cloth going up and turning around real quick.

@vancliff

Ahhh. Blendshapes. I think I will splice your method with what animatedfox did. If I can even hit that point. Shall see how. But a mish mash might work.

Kinematics
11-30-2010, 06:38 AM
Hey @animatedfox, I was just testing it out but could you go into more detail on how to go about using another curve as an up vector? Does it happen to the geometry or the curve and isit the same up vector that is in the aim constraint?

animatedfox
11-30-2010, 01:47 PM
We used the offsetCurve to for a target for our aim constraints...Unfortunately some in-house script was used to do this easily...not sure how they set that up originally. But the offsetCurve also served as a visual representation so that the animators knew when some flipping was about to occur and change the aim type if need be.

I will stress the importance of creating a way to control the tied bow separate from the controls to actually tie the knot. As I mentioned the basic tying was done with bunch of controls along the ribbon 12 course controls 60 detailed controls as well as a motion path to create the base U shape around the object. Then once the bow is formed, but not really tight we had lattices to tighten and add bounce to the bow ends. They were rigged like little 5 joint FK chains that could be freely placed around the areas we needed to control and then animated.

I will see if I can find out more about the offsetCurve aim setup.

Kinematics
12-01-2010, 12:50 AM
Yes please animatedfox. I am probably going to skip this stage in the project but things that I hate that clients ALWAYS come back with.

Flying ribbons, tying knots, explosions, bunch of images that when pulled out makes a whole other image. I have so much work to learn all this stuff and retain it all. arghhh :banghead: =) thanks for the tips everyone!

@howardm omg you worked on Scott Pilgrim. Everyone in the office sat down over for a bluray of that movie. The work is pretty awesome =)

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12-01-2010, 12:50 AM
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