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Bug 1713

Summary:	Comparison between two quaternions modulo 2*pi
Product:	Eigen	Reporter:	Vincent Samy <vsamy>
Component:	Geometry	Assignee:	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
Whiteboard:

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

Hello,

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?

Best,

Vincent S.

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

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