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#Actualquasar3d

Posted 21 November 2013 - 05:36 PM

Checking if lengths are multiplictive (ie. the length of a product is equal to the product of the lengths) is actually a very good way to check if your quaternion multiplication works well (if it's multiplicative, your multiplication code is either correct or very wrong, but not a little bit wrong:)). So this was already quite a hint that there was a problem with your multiplication.

 

Note that for any quaternion a * conj(a) gives the square euclidean length, and so

 

|a * b|^2 = a * b * conj(a * b) = a * (b * conj(b)) * conj(a) = a * |b|^2 * conj(a) = a * conj(a) * |b|^2 = |a|^2 * |b|^2


#1quasar3d

Posted 21 November 2013 - 05:35 PM

Checking if lengths are multiplictive (ie. the length of a product is equal to the product of the lengths) is actually a very good way to check if your quaternion multiplication works well (if it's multiplicative, your multiplication code is either correct or very wrong, but not a little bit wrong:)). So this was already quite a hint that there was a problem with your multiplication.

 

Note that for any quaternion a * conj(a) gives the square euclidean length, and so

 

a * b * conj(a * b) = a * (b * conj(b)) * conj(a) = a * |b|^2 * conj(a) = a * conj(a) * |b|^2 = |a|^2 * |b|^2


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