social.noyu.me

this is very embarassing to ask about for me but does anyone in my audience understand why Apple's CGAffineTransform is defined as mapping to a matrix where the last column is (0, 0, 1) and the last row is (tx, ty, 1.0); shouldn't it be the other way around? when does this work?

@hikari depends whether the coordinates are considered row vectors or column vectors. You need the transpose of the transform entirely depending on the convention.

@porglezomp as i realised in https://social.noyu.me/@hikari/statuses/01JM5Y8ZQB4C7D0MY2MMA84SDV

apple write:

row times matrix

i think i am used to:

matrix times column

if i transpose the matrix are they equivalent?

@hikari yes, A•x = (xT•AT)T