On Tuesday, 26 May 2020 09:17:05 PDT Edward Welbourne wrote: >> (Matrix multiplication isn't commutative.)
Thiago Macieira (26 May 2020 18:42) > This more or less summarises all I remember from matrix classes from high > school. While I'm a linear algebraist ... and aware that the orthodoxy of graphics programming does things "a bit differently" than linear algebraists do, but allegedly for good reasons (that I might one day learn). It's just the same thing written differently. >> I'll try to work out whether QMatrix / QTransform are consistent about it It seems QTransform was the only one in question here; and its matrices are the transposes of what I would have expected; hence its multiplication happens in the reverse of the order I expected. This is a self-consistent way to do things, just confusing to those who think they know how matrices work. It turns out that either way round works fine, as long as you're consistent. Which QTransform appears to be; and its docs correctly describe it the way it is. Eddy. _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development