How to set up Reaction manager to control skin morph (Max)

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Old 04 April 2013   #1
How to set up Reaction manager to control skin morph (Max)

I'm having a problem trying to skin a character. I was using skin morph to correct deformations, but it don't works well with joints that can rotate more than one angle (like the shoulder or the upper leg), as it removes the skin morph influence if you rotate the bone in 2 of those angles instead of only rotating one.

To solve that, I wanted to use reaction manager to control those morphs depending on the bone angle but I'm not sure how to configure it. Right now my stack looks like this:

- Skin Morph
- Skin
- Editable Poly

I thought the best way to do it is adding a morpher modifier below the skin modifier to control those joints, so it looks like this:

- Skin
- Morpher
- Editable Poly

I'm able to configure Reaction manager to control those morphs as the bone is rotated, but I can't find a way to convert the morphs I've already done in that Skin morph modifier with the bone rotated to morphs that work in that new morpher modifier.
I've tried rotating the bone, turning off the skin modifier and making a snapshot, but if I add that snapshot to the new morpher modifier, the deformation I get looks completelly different than the one I had with Skin Morph.

Anybody know if I'm configuring this correctly or if there's a better way?
And in case this is the correct way, how can I convert the morph information in the skin morph modifer to morpher information that works well?
Dani Garcia
Old 04 April 2013   #2
hey Dani,

I'm not sure you can do that, max's morphs are reading the vertex position in world space and that's why once skin is applied, the deformation you get from the morph is incorrect, you would need that vertex position in tangent space somehow, there's the same problem in maya but there are tools to deal with it. I'm not too sure how to do that in max. what problem do you have exactly with skinmorph? I don't recall having problems with more than 1 angle of rotation but haven't used in a while...
Old 04 April 2013   #3
Hi Alex,

I did a few tests but I couldn't find any way to do that, so I started thinking other ways to do it.

The problem I had is that skin morph influences were loosing strenght when rotating 2 different axis.
For instance, I started rotating the leg upwards (with the knee close to the chest) and created a morph that made it deform well. After that, I rotated the leg in another axis (opening the leg to the outside of the body, for instance) and then the problem appeared, because the morph I created to fix the upwards deformation was something like 50% strenght instead of 100%, even if the leg was still rotated upwards.
In other words, I was able to fix the shape when rotating the leg upwards or to one side, but not when doing both movements at the same time (like sitting with the legs open).

I've found a solution that seems to work more or less, but I'm not a professional rigger, so probably there's a better way to do it. I used the "ExposeTransform" helper to get the information of the leg bone in this case (as I'm using a biped and can't link the rotation value otherwise) to wire each axis rotation to a separate helper. So I had 2 helpers placed in the pivot point of the leg, and one of them that was only rotating on the 'Y' axis but not on the other 2, and the other one in the 'Z' axis but not on the other 2, and I used them as bones instead of the leg bone in the skin morph modifier. That way I can move the leg upwards to get the 100% of the deformation, and if I rotate the leg outside, the helper won't follow that rotation, so the morph will still be 100%.

Not sure if I explained it in a way it can be understood.
Dani Garcia
Old 04 April 2013   #4
Hi Dani,

yes I guess that makes sense using different helpers for different axis since skinmorph apparently will fail with that. Why do you need the expose transform tool? can' t you just orient constraint the 2 helpers to the legs so you avoid having too many nodes in ur scene..?
Old 04 April 2013   #5
Hi Alex,

Do you mean using the wire parameters tool directly on the legs or to lock the rotations on 2 of the axis for those helpers?

If it's the first, I think I can't do it as I'm using a biped, and I coudn't find the way to link any rotation axis if it's a biped object, as it seems to use a special controler for the basic transformations. That's why I had to use expose transform to get that value. Maybe there's another way to get those values, but I haven't rigged enough to know it.

If it's the second, I really didn't thought about that, I'll check if that works too. Right now everything is working well, so I probably won't change it, just in case, but I'm curious to see if there's a better way to do what I did so I will test it.

Grącies per la ajuda!
Dani Garcia
Old 04 April 2013   #6
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