How to interpolate rotations?

Question

I have two vectors describing rotations; a start rotation A and a target rotation B. How would I best go about interpolating A by a factor F to approach B?

Using a simple lerp on the vectors fails to work when more than one dimension needs to be interpolated (i.e. produces undesirable rotations). Maybe building quaternions from the rotation vectors and using slerp is the way to go. But how, then, could I extract a vector describing the new rotation from the resulting quaternion?

Thanks in advance.

Answer 1

Since I don't seem to understand your question, here is a little SLERP implementation in python using numpy. I plotted the results using matplotlib (v.99 for Axes3D). I don't know if you can use python, but does look like your SLERP implementation? It seems to me to give fine results ...

from numpy import *
from numpy.linalg import norm

def slerp(p0, p1, t):
        omega = arccos(dot(p0/norm(p0), p1/norm(p1)))
        so = sin(omega)
        return sin((1.0-t)*omega) / so * p0 + sin(t*omega)/so * p1


# test code
if __name__ == '__main__':
    pA = array([-2.0, 0.0, 2.0])
    pB = array([0.0, 2.0, -2.0])

    ps = array([slerp(pA, pB, t) for t in arange(0.0, 1.0, 0.01)])

    from pylab import *
    from mpl_toolkits.mplot3d import Axes3D
    f = figure()
    ax = Axes3D(f)
    ax.plot3D(ps[:,0], ps[:,1], ps[:,2], '.')
    show()