[connect.audit] Quaternion Interpolation.

peterl@ibmpcug.co.uk (Peter Leaback) (05/06/90)

A formula for spherical linear interpolation from 'Q1' to 'Q2' with
parameter 'u' moving from 0 to 1 is

              sin (1-u)O          sin uO
              ----------  Q1  +   ------  Q2
                sin O             sin O

where  cos O = Q1.Q2

This guess this produces the optimal movement over the 4D sphere.
The problem that I face is that this movement is definately NOT the
optimal movement through 3D space.

Take an example, Q1=(0.422087,0,-0.905792,0)

                 Q2=(0.015536,0,0.999879,0)

The angle between these quaternion's is about 155 degrees, but the angle
between the direction vectors these quaternions represent is 50 degrees.

Is this a well known problem ? Have I made some mistake ?

Pete Leaback.

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