Hi @owen, thanks for following up.
As @m_adam has already pointed out there's actually no difference in the values defininig a matrix representing a rotation on -30, -390, 330 or 690 on a certain axis.
The lifesafer in this case is to use the already mentioned GetOptimalAngle which actually provides you with the HPB vector that would minimize the rotation given the previous HPB and the current HPB.
For the sake of completeness let's assume that at frame 0 H = 0 whilst at frame 1 H = -5.
Running the following code just returns the "expected" HPB vector
def main():
# set the lastHPB to the previous frame value (in this case zero)
lastHPB = c4d.Vector(0,0,0)
# retrieve the current rotation order
rotOrder = op.GetRotationOrder()
# convert from matrix to HPB representation
currentHPB = c4d.utils.MatrixToHPB(op.GetMg(), rotOrder)
# get the optimal HPB vector
optimalHPB = c4d.utils.GetOptimalAngle(lastHPB, currentHPB, rotOrder)
print optimalHPB
Now using this strategy and knowing the HPB of a clone at the previous frame, you are able to obtain a meaningful HPB representing of the matrix describing the rotation at the current frame of a certain clone (or object).
Best, Riccardo
