Advice re: rotating, moving bones and rig.

Hi all,

I’m trying to animate a low-poly character I plan to use in a game, eventually.

I have a pretty good mesh, which deforms nicely, and a basic rig I created based on David Ward’s ‘Alien’ tutorial on CGCookie.com

I’m now trying to animate some poses, like an idle pose, and some actions like walk and run cycle.

However… when trying to move and/or adjust some of the bone positions I feel as if I must have swallowed a bottle of stupid pills or something. :o

I absolutely cannot get the bones and joints to rotate the way I think they should move. I’m sure it’s ignorance on my part, but not sure what I’m doing wrong.

In the image below I’ve circled some of the problem areas. For example, on the arm I want to be able to rotate the upper arm along the X-axis, to bring the elbow backwards. But I can’t seem to do anything but rotate that bone along it’s normal Z-axis.


Any help and suggestions are most welcome!

Thanks,
MD

Hi SB,

it looks like you have set up IK for your rig. With the IK for the arm for instance you can pose the arm by moving the IK target rather than the bones that are part of that chain. Setting up pole targets or limit rotation constraints on the joints, eg not letting the elbow rotate backwards, will give even better results. Bones in the IK chain are under the influence of that constraint… eg the position of the IK target.

They rotate along their axis … bone roll … because that offers a degree of freedom… like if you put your hand in front of your face… your shoulder and elbow rotations are pretty much fixed for that hand position… but if your bones could roll longitudinally ie spin on the inside that wouldn’t affect your hand position.

So… I have an IK bone in the foot… I should also have one for the knees and elbows basically? Should I have one for the shoulders as well.

Sorry, I’m pretty new to rigging and not sure how to set these up. I guess I will just experiment until I find something that works?

MD

No. what I’m saying is that the IK is set up to enable you to pose the whole chain by moving the target. Moving your HandIK bone will make the arm bend at the elbow and shoulder to accommodate the hands position. The chain length is how far down the skeleton the target has influence. The bones are color coded to help you out.

So try posing your arms legs by only moving the IK target bones. Without a sample it’s hard to see whether your setup is correct but if it is you will see what I mean easilly enough.

Maybe download a couple of the free rigs availabe… Revolt Randy has one in his sig for example and have a play around to see how these have been set up… and don’t worry about “stupidity” or “ignorance” etc we’ve all been there done that… well I’m damn sure I have and still do… hehe.

skeleton_1.blend (524 KB)

I’ve attached the .blend file of my rig so (maybe) you’ll be able to see what I mean.

When I move the IK_hand bone, the arm does follow. But it never bends at the elbow until I really force it upwards. Otherwise, the whole arms just stays stiff. So I can’t get a nice, relaxed arm pose.

MD

Hey thanks for the plug batFINGER!! :smiley:

SeriousBlacknes - the link batFINGER refers to is in my signature at the bottom of this post. It will take you to another thread here where you can download the character and there is also a link to a video showing how to use the character. Also, here’s a link to a video tutorial I did on what fk & ik is, when each is useful, etc, etc…

Hope this helps,
Randy

Hate to double post, but I just saw your post with your .blend file and looked at it. One thing I noticed is there is no ‘pre bend’ to the arms, same for the legs. A little bit of ‘pre bend’ in the direction you want to bone to bend is helpful. In edit mode, grab the joint between upper and lower arm bones and move it backwards just a bit. Also, most of the time, I just use IK for the arms and not the shoulder, try reducing your chain length in the ik constraint by 1.

Randy

Alright, I’ll check make those adjustments and update the thread when I’ve made some more progress.

I’ll also check out your rig as I’m sure there’s a lot to be learned for examining it.

MD