# [Interest] Plane rotations

Sean Harmer sean.harmer at kdab.com
Wed Apr 5 14:13:24 CEST 2017

```Yes, just use the dot product.

Sean

On Wednesday 05 April 2017 14:59:48 Igor Mironchik wrote:
> Hi,
>
> I Googled it and found:
>
> The cos of angle between vectors is:
> |(ax*bx + ay*by + az*bz)
>
> -------------------------------------------------------- sqrt(ax*ax +
> ay*ay + az*az) * sqrt(bx*bx + by*by + bz*bz)|
>
> 05.04.2017 14:52, Igor Mironchik пишет:
> > 05.04.2017 14:45, Igor Mironchik пишет:
> >> Hi,
> >>
> >> 05.04.2017 14:29, Paolo Angelelli пишет:
> >>> Just cross N and M to get the vector around which to rotate.
> >>>
> >>> Then use a QQuaternion to set the rotation in the Qt3DCore::QTransform,
> >>> and construct it with fromAxisAndAngle(const QVector3D &axis, float
> >>> angle)
> >>
> >> Ok, I can rotate around the right axis. But what angle should I rotate?
> >
> > This is my question.
> >
> >> And how can I calculate new normal to the rotated plane?
> >
> > I already know it...
> >
> > I just need to know what angle should I rotate.
> >
> >>> On Wed, 5 Apr 2017 14:18:56 +0300
> >>>
> >>> Igor Mironchik <igor.mironchik at gmail.com> wrote:
> >>>> Hello,
> >>>>
> >>>> Let's say I have two vectors - N (normal vector to plane P1) and M
> >>>> (normal vector to plane P2).
> >>>>
> >>>> How to calculate x, y, z axis rotations angles for plane P2 to make
> >>>> plane P2 parallel to P1?
> >>>>
> >>>> How to calculate x, y, z axis rotations angles for plane P2 to
> >>>> rotate it
> >>>> around vector N?
> >>>>
> >>>> Thank you.
> >>>>
> >>>> And what is the measurement of angle in rotationX() of
> >>>> Qt3DCore::QTransform?
> >>>>
> >>>> I need to calculate angles in this units.
> >>>>
> >>>> _______________________________________________
> >>>> Interest mailing list
> >>>> Interest at qt-project.org
> >>>> http://lists.qt-project.org/mailman/listinfo/interest
> >>>
> >>> _______________________________________________
> >>> Interest mailing list
> >>> Interest at qt-project.org
> >>> http://lists.qt-project.org/mailman/listinfo/interest

--
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
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