Transform node question...

Anonymous — Fri, 01 Jan 2016 15:38:04 GMT

Hi,

I am trying to understrand the transformation matrices used in "transform" node. According to maya docs, the final transformation is :

matrix = SP(-1) * S * SH * SP * ST * RP(-1) * RA * R * RP * RT * T

I know it's a row major, so if we use a fixed frame logic (i.e. fixing world coordinates and actively transform objects), we can read the matrix from left to right (i.e. post multiplication) as : scale pivot inverse translation SP(-1), then scale S , then shear SH, then going back to the same pivot point...

My question: I don't understand why we need

(1) scale pivot correction ST (SP-1 cancels SP, so why need ST? getAttr transform.spt always returns 0 0 0 )

(2) rotation pivot correction RT, (as above RP-1 then RP, why need RT) and

(3) RA

Can anyone provide a case where ST/RT/RA are needed? Is there any document/pdf/papers that explain the needed for these three matrices? I found lots of resources on transformation matrices but could not find any these docs that explain any possible need for these matrices...

Thanks in advance,

topic Transform node question... in Maya Programming Forum

Transform node question...