Help with rigging a shoulder bag to a body

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Hi. I have a character that has a small over shoulder bag with a long strap. The bag hangs at his right hip, and the strap goes across his chest and back, over his left shoulder. Is there a way to rig it up to be able to have the strap deform as his body deforms, but if he leans forward or back or jumps, the strap must be able to rotate and have the bag swing down in front of him or behind? A bonus, but not totally necessary is to have it possible to be taken off too.

Thanks for any help or suggestions

[Jho]

I would probably just make a few bones that control the strap and parent them to the closest spine bones...

BUT now that I think of it. One way that just came to mind that might be fun to try:

-Make a spline in the shape of the strap and weight that similarly as the character (just select the spline, pick Deform>Envelope>Set Envelope and pick all your character's bones. The automatic weighting will most likely be good enough). GATOR didn't work for some annoying reason :C


-Create some nulls and path constrain them on the spline you just created (for instance first 0%, second 25%, third 50%...), name them "strap_helper_bones" or something.


-Then just duplicate the nulls and name the duplicates as "bones", or "deformers" or what ever. Set them as childs of the helper nulls and you're pretty much done.
I would hide the helper nulls.



So now the bones will follow the movements of your character's body and you can tweak single bones by animating them normally. I would probably add a slider of some kind to tweak the path% of the helper nulls and what not, but here's the basic idea. Hope that helps at all.

[colour]

Thanks Jho.

I had just started a very similar test, with the curve skinned to the body, but then deforming a long thin cylinder to the curve. Make clusters with centres along the cylinder, and I could constrain the bag to those clusters (similar to placing of nulls along the curve as you suggest). The cylinder could simply translate along the curve with the built in slider on that ppg. Similar to your idea I think

[colour]

Hi all

So I rigged up the bag. The quick explanation is:
- envelope a curve to the body.
- constrain a cylinder to the curve
- pose constrain nulls to the segments of the cylinder
- parent a second set of nulls to the first, to give a second level of control
- envelope the bag to the second set of nulls.

I tested the bag out and the strap deforms nicely with the body, and I can spin the whole bag around the body using the curve deform - translate along curve slider. It all works great

UNTIL It comes to animating! The bag can be keyed on frame 1 and 2. After frame 2 the bag geometry remains behind and only the curve and nulls behave as they should.

I have no idea what's causing this. The weight points are visible on the bag, but it won't move after frame 2.

Please help if you've come across this type of thing.

[colour]

Ok, I froze the bag mesh completely, then re-imported the envelope, which I had saved via Gear, and it seems to have fixed whatever corruption there had been before. I hope

[missingkey]

I typically use a few nurbs straps for things like this.

Basically, make a nurbs strap like you did the curve. Gator the weights from the body to the nurbs. Cluster constrain null/controller/deformers hierachy to the nurbs strap (how ever many controls you want). Duplicate the first nurbs, and deform it using those deformers you just made. then on the second strap, cluster constrain lot's of nulls to it. Create and poly objects from one of the nurbs straps, increase the resolution of it. Use the deformers attached to the second nurbs stap on this new poly objects. Smooth the weights to be nice, then gator the weights from that poly object onto the Bag geometry.


So essentially, the 1st nurbs strap deforms with the body. which then has offset controls to deform the 2nd nurbs strap, that has lots of nulls constrained to it, that deform the final geometry.

i think that's the pretty good way of doing it. or using a "doritos" approach on the nurbs.

Goodluck