Qt3D - How does a camera provide its view matrix

Conninho

Hi everyone,

I have a question on cameras in Qt3D:

While Qt3D provides its own QCamera class, it is stated in the documentation of the QForwardRenderer class that

Note: A camera is a QEntity that has a QCameraLens as one of its components.

(The fact that the camera property of the QForwardRenderer is of type Qt3DCore::QEntity* backs this up.)

So if I write a custom camera (by subclassing QEntity), what do I need to do to provide a view matrix? While the projection matrix is given by the QCameraLens, the view matrix needs to be provided by the camera entity itself somehow. Or am I misunderstanding this?

Thanks in advance for any help!

Conninho

Ok, I toyed around a little and figured it out myself:

A QEntity element that is used as a camera can, just like other (visible) QEntity elements, be positioned by attaching a QTransform component, and the view matrix is automatically induced by the camera entity's global transform (just like a visible QEntity's model matrix is induced by its transform).

So the functionality of a QTransform object seems to be much more genral than its - optimistically named - Detailed description in the doc suggests:

"Used to perform transforms on meshes"
;-)

Big thanks to the Qt and KDAB team for Qt3D, which seems to be an awesome 3D module. Waiting patiently for more documentation...

m.sue

Hi,
the latest QT3D documentation, so far, is here: http://doc-snapshots.qt.io/qt5-dev/qt3d-cpp.html
But e.g. QTransform did not change much yet.
-Michael.

Conninho

@m.sue That's good to know, thanks for the link!