Radial/ulna twist

[kepeli]

I am trying to set up the radial/ulna rotation on my characters arm but can't get it to look convincing it still looks like it is being wrung out.

I have a skeleton set up which includes an additional joint midway betweent the elbow and wrist joints for this rotation. However, I cannot achieve a nice gradual twist on the joint. I have tried assigning flexors to the joint and moving and scaling them but its still not right. Perhaps I'm just not using them correctly.

Any ideas how I can solve this using my current character setup?

Regards,

Stuart.

[dougr]

I saw the radial/ulna twist setup on the Mastering the Human Character in Maya video with Chris Landreth. He set the radial/ulna rotate joint close to the wrist joint not in the middle of the forearm.

He also set a lattice on the forearm. It gave a nice twist.

I am going by memory here, so I apologize for not being to detailed.

If you can get the video, he does spend some time on this area.

Hope it helps.

[fredc]

I don't know what technique is descibed in the video, however here is something that has worked for me.

1. Create your radius and ulna with two single joint skeletons.
2. Imagine the arm laying flat on a table, with the palm facing inside like you were clapping (or a Kirate Chop). Now creat a small single joint skeleton, between the attachment of the ulna and the radius. It should be verticle with the origin on the ulna side touching the table.
3. Constrain the radius and ulna skeletons to the wrist skeleton. the Ulna should connect to the origin and the Radius to the effector.
4. Now try to rotate the palm, by moving the effector of the wrist around it's origin, and move the ulna over slighty.

If you observe your own forearm you will see that the ulna hardly moves while the radius orbits arount it. This set up simulates this.

Hope this helps,
Urp

[kepeli]

I have the video and this was how I initially set up the skeleton but I have found that by moving the ulna joint back a bit the effect improves. I haven't been able to assign the twsting lattice as on the video. It misses out this part. Do you know how its done? I thought it would be a simple case of skinning a lattice to this part of the skeleton and assigning the forearm area to the lattice. However, I cannot get it to twist gradually. It might be a case of rotating each set of CVs on the lattice and using set driven key.

Any ideas?

[dougr]

I had another idea. You may have already done this, but...

have you painted the skin weights for the forearm to have less influence from the ulna joint? Less influence may help stop the wringing look.

As far as skinning the lattice, I have always applied the lattice to object then select the lattice and joint then skin. So you are skinning the lattice not the object itself.

The post 2 threads up may help too.

hope this helps.

doug

[nieder3d]

-anyone who disagrees I apologize, but that A|W set-up sucks!
-I've created a nifty radial ulna arm set up you can download from: (type it into your Browser)
ftp://sid_arm:h3dsidarm@ftp.sidgrafix.com
please donot upload to this, I am sharing it with any one who wants it...
it is the zip labeled sid_arm feel free to grab anything else from here..
-Just an alternative, maybe even give you an idea of your own...

sid
sid69graphic@yahoo.com
"-if it wasn't for '"Y, we wouldn't be..."

[kepeli]

I've done it!

I moved the ulna back to the position in the A|W video, assigned a lattice to the forearm area and skinned this to the arm. I then used a cluster to weight the lattice deformation.

Its not perfect but it should do all it needs to do in this animation.

Thanks to everyone for your suggestions.

P.S. Sid, I have a copy of your arm setup. I'll take a good look at it once I finish this project.

Stuart.