
Re: Nx2N lapped orthogonal transform
Posted:
Aug 20, 2013 4:03 PM


On 8/20/2013 3:42 PM, quasi wrote: > 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.
ouch, indeed! :)
 Nicolas Bonneel

