Random Rotation of Points using Householder matrices

Asked Jul 02 '14 at 23:24

Active Jul 02 '14 at 23:26

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I have $N$ points in $D$ dimensions, were $D$ is big, for sure more than $100$. $N$ is also big.

The goal is to produce an algorithm in my code, that will take as input this dataset and will give another one (in a different matrix), that will be randomly rotated.

I have used Euler rotation, but the time complexity of it is $O(N\cdot D\cdot D)$.

Chanop and Hartley note in their paper "Optimised KD-trees for fast image descriptor matching", that:

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but searching the internet didn't help me much, so I literally don't know how to perform this task. I am not asking for code, but for guidance, for what I should do to achieve my goal.

A relevant -maybe- question is this in this site.

edited Apr 13 '17 at 12:19

Community

asked Jul 02 '14 at 23:24

gsamaras

What's the question? Do you know how to multiply a Householder matrix and a vector in $O(d)$ time? That I can do. The second part I cannot do, because I don't know what a tree is. – Stephen Montgomery-Smith Jul 03 '14 at 02:16
Also, how do you use Euler rotations if $D \ne 3$? – Stephen Montgomery-Smith Jul 03 '14 at 02:19
Multiplying by householder matrices does reflection not rotation. You could try Givens rotations. – daw Jul 03 '14 at 08:21
I used the generalizations described in the link. Yes that was the case, but after daw's comment, everything got cleared up, tnx! – gsamaras Jul 03 '14 at 12:50

Random Rotation of Points using Householder matrices

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