Averaging two rotations

Here's another rotation question. Say I have two rotations and I want a rotation that is somewhere in-between the two of them, how would I go about this?

For example, I have one rotation pointing 45º to the right, and one pointing 45º to the left, I want to calculate a rotation that is a weighted value composing 60% of the first rotation, and 40% of the second, the result of this should be a rotation pointing 9º to the right.

Is there an easy way to do this? I could probably come up with a messy way to do it by converting both rotations to Euler vectors, but it would likely be imperfect. Can this even be done using only the rotations?

I'm hoping someone has a brilliant solution to this as I have been working on something very similar. As I follow along a defined path, when I change directions, I want to place a prim at that spot and rotate it to split the angle of the change of direction.

I have been working with llAtan2 to try to accomplish it. I have gotten close, but haven't quite gotten it right.

I can post some sample code later tonight if no one else comes up with an answer before then.

I would convert the two rotations to vectors in space, take the mean and convert back to a rotation.
Something like this:

rotation Ra =...;
Rotation Rb =...;
vector Va = llRot2Axis(Ra);
vector Vb = llRot2Axis(Rb);
vector Vm = 0.5*(Va+Vb);
rotation Rm = llAxes2Rot( < Vm.x, 0.0, 0.0 >, < 0.0, Vm.y, 0.0 >, < 0.0, 0.0, Vm.z >;

Happy rotating
It does not look as if 'llRot2Axis' and 'llAxes2Rot' do what I want them to do. The concept has to be fiddled with

My eyes glazed over while reading that. But I now have bettter ways of doing it than what I was trying.

I will rework my code tonight. I hope the OP is getting help too.

Thanks Hewee and Dora (and Haravikk for asking this)

That thread has a very concise function that seems like it would do what I need, I've yet to try it but I'll cross-post Strife Onizuka's modified version:

rotation slerp( rotation a, rotation b, float t ) {
return llAxisAngle2Rot( llRot2Axis(b /= a), t * llRot2Angle(b)) * a;
}//Written collectively, Taken from http://forums.secondlife.com/showthread.php?p=536622

Thanks for the help!