When turned on, fixed particles will not rotate at all.
When set to OFF, fixed particles will rotate in the direction of moving particles that are linked.
Line Avarage Rotation
Automatically adjusts the final particle rotation in a structure where each particle is connected by a line, such as BoneCloth.
This function is always ON and cannot be turned OFF.
Specifically, the rotation of particles (cube in the image) is automatically adjusted according to the angle of the line as shown in the following image.
[Line Avarage Rotatin] adjusts the particle rotation according to the average angle of the connecting line.
Normally, turning this function ON will produce smoother results.
When [Line Avarage Rotation] is turned off, the rotation of particles is fixed in the line direction of the connected child.
This is useful for things like earring movement.