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Bug 1713

Summary: Comparison between two quaternions modulo 2*pi
Product: Eigen Reporter: Vincent Samy <vsamy>
Component: GeometryAssignee: Nobody <eigen.nobody>
Status: NEW ---    
Severity: Wrong Result CC: chtz, gael.guennebaud, hauke.heibel, jacob.benoit.1
Priority: Normal    
Version: 3.3 (current stable)   
Hardware: All   
OS: All   

Description Vincent Samy 2019-05-14 00:56:12 UTC

So i bumped into a problem with quaternion function `isApprox` that tells whether or not two quaternions are the same. Though, quaternions can represent the same rotation and have different values. Here is the code.

Eigen::Quaterniond q1 = Eigen::Quaterniond::UnitRandom();
Eigen::Quaterniond q2(-q1.w(), -q1.x(), -q1.y(), -q1.z());
q1.isApprox(q2); // return false
q1.angularDistance(q2); // return 0

q1 and q2 represent the same rotation (modulo 2*pi), maybe the function should return true?


Vincent S.
Comment 1 Nobody 2019-12-04 18:38:22 UTC
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