FBIK (Full Body IK) in Control Rig seems to be size-dependent; with the default 2-meter mannequin (exported to Blender and reimported) FBIK works fine. However, if I scale up the skeleton to 10 meters (scale x 5) in blender and reimport in Unreal, FBIK will break (As attached below). I have also put the project on Google Drive.
I have looked at the Valley of the Ancient Project where the Ancient One is about the same size, which also uses FBIK. What I noticed is that the Ancient One is actually only made with ~2 meters and then scale up in the scene. I suspect this is a known issue in this IK solver? Other solvers seem to work fine.
Is is possible to not use this scale-in-scene workaround? Or if it is must, is there any correct way to do so?
Also the VotA project is not really working with preview 2… Still waiting for an update.
I actually do have the problem too!
I’ve tried to import a mech’ that is around 10 meters high and it goes wild when using FBIK but works fine with base mannequin
Spend a whole day trying to find any solution. Will try that size thing but if it’s the case I don’t understand what’s the matter between IK and skeleton world size
EDIT: I Confirm that if the mesh is shorter than 2x2 meters It works pretty. that is really strange!
Glad to know that I am not alone! I would indeed like to know if it will be sorted out soon. As far as I could tell unreal themselves in the Valley of the Ancient project only use a 2 meter character and scale it up in the scene to make it huge.
I walkaround this issue by not using FBIK, but rather using CCDIK and healing it. I may look into the FBIK.cpp in the source code which I believe is the one they used in Control Rig once I got myself a break.
Looking through PBIK.cpp code, I found it calculates the mass of the target bone based on length between bones. That means, you need to set up MassMultiplier and MinMassMultiplier to fit with the length of bone chain from Root to the effector target bone.
I have a 10m character, and FBIK works fine with MassMultiplier to 3.0 and MinMassMultiplier to 1.0.
