quasi
Posts:
12,050
Registered:
7/15/05


Re: Nx2N lapped orthogonal transform
Posted:
Aug 20, 2013 2:57 PM


Nicolas Bonneel wrote: >Robin Chapman wrote: >>Nicolas Bonneel wrote: >>>James Dow Allen wrote: >>>> >>>> Let >>>> ( A B 0 ) >>>> ( 0 A B ) >>>> ( B 0 A ) >>>> >>>> be a 3Nx3N real matrix with A,B,0 each NxN and 0 an >>>> allzeros matrix. >>>> >>>> What is the necessary and sufficient condition for that >>>> matrix to be orthogonal, i.e. that its transpose also be >>>> its inverse? >>> >>> by direct computation, AB=BA=0 and A^2+B^2=Id, right? >> >> No > >ok, but why not ? > >Noting the matrix above M, I just did M^T.M=Id and directly >computed the matrix multiplication per block.
You didn't do the transpose correctly.
The inner blocks need to get transposed as well.
quasi

