Cluster Rotation Vs Joint Rotation, Losing Shape, Rigging An Eyelid

[vinz9]

Hi,

I think I could use some explanation about how smooth skinning work vs clusters.
As you can see in the picture below, when I rotate the cluster (which has its pivot centered in the sphere), vertices with weight < 1 still follow the curve of the sphere (left side), whereas when I rotate the second joint (right side), the sphere shape is lost.

I'd like to use joints instead of clusters, since maya has built in functions for mirroring joints and weights, so is there an easy fix ?

I guess it has to do with weight normalization, but I don't really understand (also why smoothbinded vertices with all weights to 0 go to the origin instead of staying in place ?). Maths explanations are fine too.

Thanks a lot

[joojaa]

Theres no difference they are both the same thing. Just slightly different depth of scope

However plese note that in the case of your right picture you have 2 clusters! because the bone is actually 2 joints and smooth binding

QUOTE
also why smoothbinded vertices with all weights to 0 go to the origin instead of staying in place ?

They have no matrix. Skin clusters totaly take control over the entire mesh by default so there needs to be one joint for the base translation too.

QUOTE
since maya has built in functions for mirroring joints and weights, so is there an easy fix ?

Maya has tools for mirroring the normal clusters aswell.

[vinz9]

Thanks for the quick answer.

QUOTE(Joojaa @ 07/16/09, 02:12 PM) [snapback]311743[/snapback]
Theres no difference they are both the same thing. Just slightly different depth of scope
However plese note that in the case of your right picture you have 2 clusters! because the bone is actually 2 joints and smooth binding
They have no matrix. Skin clusters totaly take control over the entire mesh by default so there needs to be one joint for the base translation too.

Ok, so there is no way to get nice rotation on partially weighted vertices with skincluster.
Just as it seems there is no way to get the behavior of the skin cluster with default clusters, because if I add a second one, it is another deformer which takes place after.

QUOTE
Maya has tools for mirroring the normal clusters aswell.

In the default toolset ? Where are they ? Couldn't find anything int the edit deformers menu.
I know I can do it with mel scripting.

[joojaa]

QUOTE(Vinz9 @ 07/17/09, 04:52 PM) [snapback]311843[/snapback]
Ok, so there is no way to get nice rotation on partially weighted vertices with skincluster.

Nice leap of logic. That's not what i said. They are different because your doing something totaly different in your example, Your not dinding the same things together.

They are exactly the same thing so you can get exactly the same effect you just need to think a bit differently then you are now because your not recognixing the differences in your solutions. If you want same you need to do eaxactly the same.

Its not exactly rocket science once you actually bind things to the SAME deformers. Just youi caought mne a ta really bad time. Doing this si a ctually a 1 minute job. Please think

Frisrt delete the second joint of your bone it distracts you and make a extra joint and assign all nonneeded to that joint.
QUOTE
Couldn't find anything int the edit deformers menu.

And you wont because its not a siple menuitem. But thing if for a eye its not problem as you can just copy inherit the data.

And no im not talking mel per see because there really is tool that trasfeer s whatever to whatever as needed. Its just that it doesnt know autiomatically what to trasfeer without you telling it how. Buut is not going to need scripting just invoking right way.

[vinz9]

Thank you for your answer, but I don't get it.

QUOTE(Joojaa @ 07/17/09, 02:59 PM) [snapback]311844[/snapback]
Frisrt delete the second joint of your bone it distracts you and make a extra joint and assign all nonneeded to that joint.

Currently I have 3 joints, first joint influences non moving part of the eyelid, second joint (the one which rotates) influences moving part of the eyelid, third joint is just for visualization and is not part of the smoothskin.
What do you mean by assign all non needed to an extra joint ?
How would that be different than my current setup?

QUOTE
And you wont because its not a siple menuitem. But thing if for a eye its not problem as you can just copy inherit the data.

And no im not talking mel per see because there really is tool that trasfeer s whatever to whatever as needed. Its just that it doesnt know autiomatically what to trasfeer without you telling it how. Buut is not going to need scripting just invoking right way.

there really is tool that trasfeer s whatever to whatever as needed : where is it located ? all I know about is the transfer attributes tool which transfers only vertices, normals et uv.
Also what do you mean by copy inherit the data ?

Thanks a lot!

[doug-hines]

QUOTE
there really is tool that trasfeer s whatever to whatever as needed : where is it located ??

I wrote a script tool to do this for me about a year ago. I'll see if I can dig it up when I get home

[paudiyal]

You can solve this issue by using Dual Quaternion skinning method on your skin cluster. Switch your skinning method to Dual Quaternion and the sphere will deform maintaining its spherical shape. Dual quternion is good for maintaining volume when rotating joints with larger values. But it can also create problems if your rig has squash and stretch. In that case you can use "weight blended" instead which will allow you to specify areas to maintain weights by painting "DQ blend weight" on your mesh.
One more thing I'd like to add, if your rig is supposed to be used in Unity or some other gaming engine then sadly you can't use DQ, AFAIK id doesnt support DQ skinning yet.
Check attached image for a quick comparison.