(beginner) calculating orientation change with eulers

[astull]

I don't mean to be a bother but the modified script still yields a non-unique solution. For example, both of the following sets of eulers yield the same solution:

euler1 = [30,90,0]
euler2 = [0,0,0]

euler1 = [0,90,30]
euler2 = [0,0,0]

solution: (90, 90, 30)

I don't understand why this happens. Maybe the vector/rotation alternative may be a more practical solution.

Thank you again for your help!

[farshizzo]

Those values are correct. I'm not sure what you are expecting. There is always going to be multiple euler sets that will yield the same angle difference. The vector/rotation alternative will also yield the same value for multiple sets. For example, the vector/rotation difference between the following sets will be the same:

euler1 = [0,0,0]
euler2 = [90,0,0]

#Vector difference will be 90
#Rotation difference will be 0

euler1 = [90,0,0]
euler2 = [180,0,0]

#Vector difference will be 90
#Rotation difference will be 0

From your first post it seems you are interested in the relative error between the two orientations. I don't see how having non-unique solutions affects this. Maybe I'm misunderstanding your original request.

[astull]

Yes, indeed! There are likely to be multiple euler sets that yield the same displacement errors. Sorry for being so bone-headed.

[farshizzo]

No worries. I know how confusing all this 3d math can get.

Would you still like me to provide you with the vector/rotation alternative?

[astull]

Yes, it would be helpful if you could offer a script for calculating the vector/rotation. Fewer variables makes the analysis much easier.

Thank you.

[farshizzo]

Here is the vector/rotation code:

import viz
viz.go()

euler1 = [0,0,30]
euler2 = [0,5,-30]

def ComputeAngleDifference(euler1, euler2):
	m = viz.Transform()
	
	#Extract forward/up/side vector from euler1
	m.setRot( vizmat.EulerToAxisAngle(euler1) )
	d = m.get()
	forward1 = d[8:11]
	up1 = vizmat.Vector(d[4:7])
	
	#Extract up vector from euler1 without roll
	m.setRot( vizmat.EulerToAxisAngle(euler1[0],euler1[1],0.0) )
	d = m.get()
	up1_no_roll = vizmat.Vector(d[4:7])
	
	#Compute rotation around forward vector of euler1
	roll1 = vizmat.AngleBetweenVector(up1,up1_no_roll)
	if (up1_no_roll.cross(up1) * forward1) < 0.0:
		roll1 *= -1.0
	
	#Extract forward/up/side vector from euler2
	m.setRot( vizmat.EulerToAxisAngle(euler2) )
	d = m.get()
	forward2 = d[8:11]
	up2 = vizmat.Vector(d[4:7])
	
	#Extract up vector from euler2 without roll
	m.setRot( vizmat.EulerToAxisAngle(euler2[0],euler2[1],0.0) )
	d = m.get()
	up2_no_roll = vizmat.Vector(d[4:7])
	
	#Compute rotation around forward vector of euler2
	roll2 = vizmat.AngleBetweenVector(up2,up2_no_roll)
	if (up2_no_roll.cross(up2) * forward2) < 0.0:
		roll2 *= -1.0

	#Compute angle difference between forward/up/side vectors
	forward_diff = vizmat.AngleBetweenVector(forward1,forward2)
	rotation_diff = abs(vizmat.AngleDiff(roll1,roll2))

	return forward_diff,rotation_diff
	
print ComputeAngleDifference(euler1,euler2)