Hello,

I've wrote a simple programm:


#include <iostream>
#include "../Eigen/Geometry"

using namespace Eigen;

int main(void)
{
Vector3f a(1,0,0), b(0,1,0), c(1,1,0);
Quaternionf q1, q2;
q1.setFromTwoVectors(a,b);
q2.setFromTwoVectors(a,c);

std::cout << "\n" << q1.slerp(1, q2).toRotationMatrix().eulerAngles(2,1,0) << "\n";
std::cout << "\n" << q2.slerp(1, q1).toRotationMatrix().eulerAngles(2,1,0) << "\n";
return 0;
}

output:
0.785398
-0
0

1.5708
-0
0

My expected output:

-0.785398
-0
0

+0,785398
-0
0


I thought a slerp rotates one rotation into another, but in this case it didnt happen.
The first slerp rotates the orientation away and not into the secound orientation.

i thought it works dimilar to Quaternion q; q.setFromTwoVectors(...);

The problem is, i didnt find much information about slerps..
I dont want to go that deep in quaternions, I just want to use them to represent a orientation.

The results are correct. q1 represents a rotation of pi/2=1.57 around z and q2 a rotation of pi/4=0.78 around z. So q1.slerp(1, q2) returns q2 exactly, and q2.slerp(1, q1) returns q1 exactly.

Hello,

iam searching for something like a rotation difference.
So if q1 is pi/2 around z and q2 ist pi/4 around z I iam looking for the -pi/4 to rotate q1 into q2.
How can i manage that?

You have to think in term of concatenation of transformations: you cancel one and apply the second:

q2*q1.inverse()

see also: viewtopic.php?f=74&t=117791

Ha thats it!

Yes I've understood it in context to Matrices.
Iam totally new to Quaternions and didnt know that it works the same way.

Thank you!