please clarify quaternion conventions in
org.apache.commons.math.geometry.Rotation
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Key: MATH-363
URL: https://issues.apache.org/jira/browse/MATH-363
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.0
Environment: all
Reporter: Albert Huang
Priority: Minor
Please clarify which quaternion convention is used in the Rotation
documentation, and provide constructor methods to use alternate quaternion
conventions.
For example, the computer graphics community has standardized on representing a
rotation of angle theta about the unit vector (i, j, k) with the quaternion
{ cos(theta/2), i * sin(theta/2), j * sin(theta/2), k * sin(theta/2) }
e.g., any introductory computer graphics textbook referring to quaternions will
describe them in this convention. This is also the convention appearing on
Mathworld, Wikipedia, etc.
The convention in org.apache.commons.math.geometry.Rotation instead appears to
be
{ cos(-theta/2), i * sin(-theta/2), j * sin(-theta/2), k * sin(-theta/2) }
Since I'm not likely to convince you to switch conventions, please at least
document the convention and provide ways to convert from the alternate (this
should be trivial?)
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