How to avoid mirrored bones from applying bone constraints differently (from mirrored target)

Hi All, being that the x axis is different in symmetrical bones in the metarig. This causes the bone constraints on symmetrically copied bones added to the rig to work opposite rotations when targeted to them. Seems it is imposible to change the axis of the metarig parent bone. I can’t find any setting in the constraints to help with this. I thought maybe the mape from setting might be negative in the mirrored one? Is there something I am missing on getting the mirrored bone to work with constraints pointed to an opposite bone? thanks!

You need to roll your bones so the X axis is the same - select the bone, press Ctrl R (it might be Ctrl T), type 180, press enter. Fixed :slight_smile:

Thanks J. The problem is I can’t get all the axis to mirror exactly. rolling it fixes the X , but messes up the Z. It needs to be flipped (mirrored) not rolled. This messes up the Transformation constraints I have

Hi @Jerny

Can you please describe what you are doing and post a .blend file? That would be the best way to get help around here…

You cannot get the X & Z axis on symmetrical bones to line up with each other on each side of the rig. You can get both sides of bones Z-axis to line up and the X-axis will be 180 rotation between the sides. You can get both sides of bones X-axis to match symmetrically and the Z-axis of the bones will be out of rotation by 180 degrees. Likewise, you could never get the Y-axis of a bone to match from the left side to the right side. The left side Y-axis points to the left, the right side Y-axis points to the right, or 180 degrees from the way the left side points.


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Thanks RR, basically trying to get the transformation constraint to work the same on symmetrized bones.
In the clip above the transformation only works when arms are in opposite rotations. Maybe an easy fix? just can’t seem to fix it
Attaching a simplified Blender file that shows the problem for me.
I Cant get “Bone.001” to work like “Bone”
Bone constraint mirror test.blend (1.6 MB)

Yeah, an easy fix. It did take me a few minutes to figure it out, but i’m a bit rusty at blender.

I had to adjust the constraint on ‘Bone.001’ to get it to match the other bone. Upper_Arm_L rotates on it’s z-axis from 0 to 70 degrees to get 'Bone" to move. Upper_Arm_R rotates on it’s z-axis from 0 to -70 to get ‘Bone.001’ to move in the same way. But the constraint on ‘Bone.001’ had to be adjusted for the input of Upper_Arm_R. The constraints min & max values needed to be set 0 for max, and -70 for min, because -70 is less than zero… The map to y-location also had to be flipped as well.

See attached file,

Bone constraint mirror test.blend (1.6 MB)

Thanks , for the fix RR.!! Ahh the “map to” as well! I wonder why? It is an exact copy of the other bone. Maybe it is based on the relationship to the target bone?..

I’m sorry I haven’t been around, life happens…

Yes, the bone - “Bone.oo1” y-axis had to be flipped because the source bone “upper_arm.r” rotation was flipped. It can be a little confusing to get used to, but it’s basically because the left and right sides are mirrored.

Hope this helps,