I am currently trying to bring to life a character that I am modeling. I already rigged it up and just started weight-painting it. To save some time, I enabled “X Mirror” in the weight painting options but it won’t work When I paint the character’s shoulder, the other one does not paint simultaneously. Attached is the file if you want to get a closer look. If you need additional informations just ask me
Go back to Object Mode, select only the model and go to Edit Mode, hold ALT and right click to select that central loop
Press SHIFT and S then Select “Cursor to Selected” to move the 3D Cursor into that selection
Go to Object mode, and in the Tool tab, click on the Origin button and select “Origin to 3D Cursor” to move the Origin to … the 3D Cursor location
Press N to open the properties panel , scroll down to the “3D Cursor tab” and look at the X value ( that is at -0.0152 )
Change that X value to 0
Now press A to select -both- your model and the armature and press SHIFT and S then “Selection to Cursor (Offset)” to move both model and armature to the new position of the 3D cursor, it will fix the slightly off center the model+armature were , that was the source of the x-mirror failing in weight paint mode
Press SHIFT+S then “3D Cursor to Center” to put the 3D Cursor back to the grid center where it was
Select your model (not the bones) and in the Tool tab similarly to before, press the Origin button and “Origin to 3D Cursor” to move it back where it was.
That’s all, now the x-mirror option of the weight painting will work.