Transfer jcms from def rig to MHX (rig) as shape keys, then over-write

[engetudouiti]

(at current this topic is just experimental idea without confirmation. just idea which I currently thinking, if we can generte more relaiable JCMs (corrective shape keys) with use daz offer JCM for MHX by script only )

It need real test, and maybe we need to modify when found new problem.

But over-write MHX jcm with new custom edit one is not so complex process.

The current problem (not heavy but annoying) is

1. After all when we convert MHX or rig-fy, (or any reliable IK FK compatible irg) their rig arrangement need to change for IK chai
2. It cause when same jcm applied, MHX rig mesh show different deform from Def Rig.

We can not avoid 1, (though maybe we can adjust IK chain (of FK chain) pos for limb, ) we should connect and all IK chain roll need to set same angle. for pole target work correctly.

So if we use current add on auto generate (and locate each bone as rest pose), rig, we need to edit JCMs.

It is not quick request, but I suppose,, after convert as new rig then set pose for each JCM max rotation value.

we can re-transfer JCMs from current Def Rig mesh to MHX rig mesh. and force to show same deform, when we input same bone rotation values.

I up-date “Corrective JCM add on” for 2.8 (long time ago and it is used as official at that time, tohugh I see some one edit again, and at current Corrective JCM add on seems removed from 3.2, but actually I have my custom version still and using it ^^;)

then it can up-date JCM shape keys, with armature modifier. I can offer the code if Thomas need to know how we transfer for posed mesh… (actually I just edit code to update 2.8 bpy change, then do not understand why it work ,, but just confirm it work and can transfer shape keys with armature modifier applied,,)

That means, we can overwrite each JCM with posing. = Transfer shape keys from def rig posing (deformed with JCM) >>> MHX rig posing (non JCM) one by one…

Though I suppose, it sitll show different deform, in middle rotation, (eg JCM bend 70 JCM will work best on 70, but when input 25 or 50, it may show slightly different deform deform def rig, I suppose,..) I suppose,, but usually may show more reliable deform when set same pose.

To make it work , we may need to compare,

def rig deform with JCM and MHD rig deform without JCM for each max rotation JCM pose. then transfer JCM to the non JCM MHX posed mesh. I suppose.

If Mesh rig pose deform is so different without JCM maybe this way not work. though I suppose.

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[engetudouiti]

hm now it seems return or have involved (or returned) in 3.2

https://docs.blender.org/manual/en/3.2/addons/animation/corrective_shape_keys.html

(but I remember there had been small issue, when we do not select shape keys in shape key panell blender 2.9 or 3.0 cause error,, so I corrected it (but at that time, no one reproted about it, so I just self-customize and used for self)

The add on can transfer shape keys from duplicated mesh (non modifier and no rig) to current posed rig (witch applied armature modifier) .

That means, when all vertex order and vertex count is same,

we can transfer Shape from Def rig mesh to MHX posing mesh. I may test again, and report here, if It can generate reliable jcm or not..

if it work well,, I suppose at least we can re-generate 4 or 5 jcm for leg and knee from def-rig jcms to MHX converted mesh. without problem. by script only…

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[engetudouiti]

Thomas

Do you think, snap or IK chain still work (eg when we set rest pose, it should return pole target pos or rotation correctly, without remain twist values etc), even though you adjust this Arm/Leg connected point?

I did not clear remember though,,, maybe to snap FK to Ik work, we needed to set this connected point as current MHX pos , to work pole and snap correctly (precisely)

if we could adjust it almost same as def rig, it may ease current problem much.. (but I do not think we can edit it, or maybe snap issue return, so I hope to confirm you)

Because, I now test transfer shape keys, but from start point (just pose X rotation 120 value for bend, MHX and def-rigs, )

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we can see clear difference for bone pivot, (MHX and def rig), so when we set same bend pose value for X rotation, it already change pose.. (as general, it is not bad pose just show different pose, but when JCM added it should cause issues) because the jcm is from delta of current def rig bone pose and deform. (not current MHX posed mesh)

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[engetudouiti]

Then I suppose it is reason why daz can not make IK <> FK compatible chain, for already offered G3. , G8 , or any genesis family rig. it remain same problem for main limb chain. (Arm and leg)

about daz studio (Non real IK snap etc), it no problem, vendor just make jcms, for daz current rig bone location rotation and each bone roll. (it effect only about FK, no need to consider IK chain constrain, and target)

but in blender such IK (FK) rig setting not work correctly when snap IK to FK chain. (so for rig-fy, we may often edit meta-rig bone roll to force ,Z axis face same direction, and adjust these connected point for chain bone, (it is same about A pose (G8) or T pose (G3))

if we do not need to snap IK FK precisely it may not matter, just force to set IK constrain, without care bone roll and algin chain, just connected all <> it usually easy cause issue when snap. and we may see often IK chain pole target not remain same pos,even though set zero pose.

So as conculusion, we may need to make new JCM s for MHX or Rig-fy. if we need clean jcm effect.

Using already generated JCM will be applied not for same posed mesh (we can not avoid it) when we input same rotation values. These small delta cause clear different deform when we set max rotation value around knee or elbow or collar area. (but we may hope to keep JCM for most of case)

I may hope if there will be new vendors who try to offer good JCMs for G3 or G8 daz importer convert rig as perfect free. (and not try to sell) from current MHX or daz importer User.

(or someone may plan to make new rig which can generate by auto and force to use daz current rig bone roll but remain IK FK snap as true meaning)