flour sack practice.

[AMkyle]

I made a flour sack with a skeleton and made an action of it kicking in the sky then coming down. but the skeleton was really hard to use, unlike the models that came with AM already. if u got any tips then itll be great if u can tell them..

 

anyways heres the video.

 

Flour_pack_kick.mov

[robcat2075]

It turns out that flour sacks are very hard to rig satisfactorily in CG, I think because the "body" is so big in comparison to the "legs" and "arms". So while animating a sack is almost a beginner exercise in 2D, it's quite an advanced topic in 3D.

 

That said, I think your sack needs to scrunch down (anticipate) before he leaps up. That's how he gets his mass moving to toss himself into he air.

[johnl3d]

here's my try at an animated sack from a few year ago

 

 

 

meatsack.mov

 

 

 

meatsack.zip

 

 

mine wasn't quite as athletic

[SplineSoup]

As an animation teacher, I appreciate the great benefit and as well as the deep frustration of animating a flour sack in 3D. A short while back I took it upon myself to put together a small library of basic characters for my students to use for class exercises and a flour sack was one of the characters I tackled. Yes. They are hard. Unfortunately, I never completed it to my own satisfaction in time for this academic year, but the concept still chews on my brain from time to time, waiting for a day when my proficiency with Animation Master matches my ambition.

 

Two suggestions for you:

 

1. Rigging. A sack of flour doesn't actually have bones, so when you rig one in 3D you'll constantly encounter problems with the sack looking too rigid. A good way to soften the effect of your rig is to use minimal bones and liberal tweaks with smart skinning. If you haven't worked with smart skins before, check out the tutorial in TAO A:M manual that either came with your CD or can be downloaded from the Hash site.

 

2. The flip is an interesting action to pull off. You'll notice that if you model your character standing on the X axis (and don't move the model bone) that it will stand on the choreography's ground plane but it will also tend to rotate from its feet. Since you're trying to get the sack to pivot around its center of gravity you might try adding a null object to your animation, placing it at the COG and linking the sack to it using the "Translate To" and "Orient Like" constraints. This way all you need to worry about is animating the arc and rotation of the null and reserve your sack rig for adding nuances like an arching back or flailing appendages.

 

There are volumes that could be said on this topic but my personal curiosity was piqued by the project file that John uploaded. I took a look at it to compare his rig to mine and am interested if any other A:M users have modeled working flour sacks. It might be worthwhile to go over different approaches and come up with a working character that could be included in the A:M library in future releases. It certainly is a ubiquitous character and the process I feel could benefit a lot of people. For consideration, here's the model I worked on last year. Feel free to use it, improve upon it, or incorporate it into your own character.

 

Look forward to seeing your work. Happy animating!

 

Chris

FlourSack_simple_altSkel3.mdl

[AMkyle]

Alright thanks a lot for all your help. i might try another thing with the sack oryour sac.

[Paul Forwood]

Here is an example of a simple flour sack which uses sim cloth to add some dynamics:

 

http://www.hash.com/forums/index.php?s=&am...st&p=234884

 

There are only five bones in the rig. A small central body bone, two arm bones and two leg bones.

[SplineSoup]

Nice tests, Paul!

 

It seems that to keep the volume of flour in the sack (and possibly even have it shift) interior deflectors will go a long way. T'would be nice if we all had Pixar's R&D department at our disposal for perfecting SimCloth applications, wouldn't it?