[Development] matrix math help needed - https://bugreports.qt.io/browse/QTBUG-84441

[Dongxu Li]

Hi,

I think the documentation is actually clear on the order by the scale()
example. I'm not sure whether we should at explicitly the concept of
intrinsic transform:

https://en.wikipedia.org/wiki/Euler_angles#Definition_by_intrinsic_rotations

The current QTransform documentation always states transforming the
coordinate system. Probably, it's supposed to be easier to understand
compared the word "intrinsic".

The order of extrinsic transforms would be exactly the opposite of
intrinsic transforms.

Regards,

Dongxu

On Wed, May 27, 2020 at 10:09 AM Edward Welbourne <edward.welbourne at qt.io>
wrote:

>
> > Here is, for example, the documentation of QTransform::scale:
> >
> >   Scales the coordinate system by sx horizontally and sy vertically,
> >   and returns a reference to the matrix.
> >
> > *Nothing* there clearly states, at least to my reading, whether the
> > "new" transform happens *before* or *after* any existing transforms that
> > the QTransform is already doing.
>
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-- 
Dongxu Li, Ph.D.
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