Copy Rotation?

I want to use the copy rotation constraint on a certain bone in my armature, but there’s nothing else with the right rotation for it to copy. I’m assuming I need to use a reference object or bone to hold the right rotation, but how do i copy/paste the rotation from the bone in my armature to the new reference object or bone, so i can then constrain the bone to it… or is there a better way?

That’s like saying “I want to copy material-X but I don’t have material-X”. Why don’t you just pose it and Keyframe the poses?


I’ll explain better then. Lets say for example I’ve already constrained a hand to the right spot to hold on to a handle. Now, when I move the rest of the model in the next frame, the hand rotates in place because it’s constrained to that spot but the rotation isn’t constrained. I need to use copy rotation so the hand will hold on to the handle properly, but theres nothing else with the right rotation for it to target. That’s why i’m thinking i need to:
a) create a reference bone or object,
b)copy the starting rotation from the hand to the bone/object,
c)then constrain the hand (copy rotation) to that bone/object,
d)reposition the model, (the hand will no longer rotate because it’s constrained to the non-moving reference object.

then remove the constraint and the reference bone/object i created. … at least thats how i’m guessing it’s done. the problem is I don’t know how to transfer the starting rotation from the hand to the reference bone/object.

OK, I see. You can use any object, but more usually a bone or an empty.

(Do you have either an IK-Solver bone or a bone with a Null constraint at the wrist? A null between the arm and the hand should have the arm calculated seperately from the hand, and a solver should not be affected by either the armature (arm) or its IK (hand) ?)


I’m not sure what you’re saying I should do. I tried putting in null constraints in different places but nothing happened, and if I unclick the IK button in edit mode it stops movement from that bone up the arm. I’ve tried to figure it out myself - done everything I can think of, with and without IK and null bones there, and different combinations of different constraints, but no luck. Thats why i’m asking you now. Could you explain exactly what I need to do, or link me to a tutorial that shows me how to do this? ( i cant find one). I imagine it can’t be that complicated…all i’m trying to do is keep the final bone(s) (hand or foot) from rotating when I move the rest of the armature.

I know I can simply use a copy rotation constraint, but for example if I use an empty and taget it with the constraint, i don’t know how to set the empty with the correct rotation. This is mainly because, if i try to find the rotation of a bone in any particular frame, if i select it and push N, it doesnt tell me the rotation.

First there’s the way constraints are evaluated:

This is (fortunately) going to change in 2.4 and will probably keep changing as the new dependancy graph is just SO extensible (and will maybe have the ability one day to be influenced by its own set of constraints)

Then, examples of Null and IK-solver:

that show what Duoas was explaining in your other thread about the Null between the lower leg and the foot or ankle, can’t remember now. Anyhow, it’s like a period between two sentences; IK punctuation.

The copy rotation constraint:
You’ll have to add the constraint and rotate the empty to get your hand back in position then Ctrl-A the Empty. Bones rotation is in eulers and all other objects in radians, that’s why you can’t find them in the N tab.


I figured out a way to do it, but it’s probably not the best way. I created a null bone for each foot and hand off away from the model, then set my copy rotation constraints to them. Now, any time i need to rotate a hand or foot to a certain position, I rotate the corresponding null bone and the hand/foot in my armature mimics it.