Qt Transform matrix

Question

I need to manipulate QML items through QMatrix4x4, in order to apply some perspective transformations. Basically, I defined the class Transform to use an object QMatrix4x4 a

Answer 1

The math Qt is performing is correct, but the frame of reference that Qt is using doesn't match up with what you are thinking.

Matrix Math:

So the components you are seeing in the math are adding shear in the x and y directions of image.

But the rotation that Qt does is about one of those axis. So if you want to do a standard 2D rotation, without shearing, you need to either not specify an axis or you specify the z axis.

The axis to rotate around. For simple (2D) rotation around a point, you do not need to specify an axis, as the default axis is the z axis (axis { x: 0; y: 0; z: 1 }).

http://qt-project.org/doc/qt-5/qml-qtquick-rotation.html

The rotation about the y axis looks like this:

Hope that helps.