Character Rigging, Gravity and Soft Body Issue

[supermarket-doubt]

As an architectural renderer, we have tons of people 3D models that are already seated, but they don't ever quite sit right in each piece of furniture. I created a quick model where I added a soft body (a pretty rigid one of course) to one of these 3D models and then added a chair and floor as colliders. This is 80% of the way there, but there is still some slumping so I want to be able to adjust the models posture.

The next step then was to add a simple character rig to the seated figures (Spine, legs and arms but no hands needed). This works great before I run the animation to adjust the position of the person as needed.

But if I run the animation so that the person "falls" into the chair and settles in, the rig doesn't move with the character skin. Is there something I am missing for the rig to follow the gravity of the soft body? I have seen some notes about "mix animation" but I am already using that with a vertex map to keep the head neck and shoulders more upright and have them be more rigid.

The idea is to be able to adjust the character after they have settled into the seat, but to do that the rig needs to follow the character as gravity takes effect.

[Sitting Test.zip] error

[Dr. Sassi]

Hi supermarket-doubt,

The file was not uploaded. For security reasons, zip (or any compressed file) is disabled. Cinema 4D as c4d files and max 1MB work. If larger, please use Dropbox, WeTransfer, Apple, Adobe, or Google Cloud services only. Please use no zip, rar, etc., during upload, and paste the URL for the file in the text; do not include an HTML wrapper or a Tiny URL. Thank you, and I apologize for the lengthy text.
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The Softbody takes over, and the Skin Deformer is no longer in use. If you take other Simulations, the result is different, but the Hierarchy drives the trouble.

My suggestion #1, use a PoseMorph.

Here, you can use a Collision Deformer result, which can be applied after disabling the Skin deformer. Which might lead to a T-Pose. So, you might want to take a copy and, in the sitting position, set the Binding Pose to new.

Now switch the Skin Deformer off and apply the Collision Deformer to the Character. (If you like to show some impact on Character.) The seat must be positioned within the Collision field of the Deformer.

If the deformation looks right, use the Object Manager > Object > Current State to Object (CSTO) to create a deformed copy. If needed, use the Magnet or Iron Tool to shape the Character's details that come in contact with the chair.

Now, you can switch off the Collision Deformer or delete it. The result of the CSTO can now be used in a PoseMorph. Apply the PoseMorph to the Character mesh and set it to Point mode.

Drag the CSTO result into the field of the Poses. I suggest to use "no" for the Alert. Set the Pose Morph to animation and the Pose slider to zero. Switch the Skin Deformer back on.

Now, you can add the impact of the chair to the Character by animating or just adjusting the slider.
Example:
CV4_2025_drs_25_CAdf_01.c4d

My suggestion #2: Do the opposite. Deform the Chair Cushion. Typically, the Barcelona Chair is not very soft, but the impact might be visible.
That means the Character becomes the Collision, and the Chair Cushion becomes the Collision Deformer. Explore the Object>Restore Slider value of the Collision Deformer.
Example:
CV4_2025_drs_25_ANdf_01.c4d

Or, a suggestion combining #1 and #2: Of course, for a close-up, perhaps a little bit of example 1 and much more of example 2 might be a good balance. For the quick Solution, use a CSTO of the cushion and sculpt the contact area into the mesh. For animation, use the PoseMorph options. I leave that to you to explore, no example.

All the best