Some people have been asking how to embed Qt painted content (and especially Qt widgets) in a 3d scene. As I've been wanting to do this ever since we added QTransform supporting fully projective transformations, I sat down and wrote a small example demonstrating these capabilities. With no further delay, I present WolfenQt:
Here's a screenshot as well for the Youtube-challenged:
A Wolfenstein like maze theme was chosen because of ease of implementation, you could of course embed a widget onto any 3d surface. The trick is to create a 3d transform mapping from a 2d plane (where the widget or other Qt drawn graphics resides) onto any quad in 3d space, and then do a perspective projection, before converting the 3d transform to a QTransform. Now, by making all the widgets and wall segments graphics items, you only need to use QGraphicsItem::setTransform() with the custom created transform and QGraphicsView will handle all event translation for you. The way the camera movement works is by recomputing and resetting every item's transform on each frame. To avoid having to continuously redraw all the widgets if they're not being updated, QGraphicsItem::setCacheMode(QGraphicsItem::ItemCoordinateCache) is the way to go.
I've embedded Qt's media player demo to show the ability to embed videos in a QGraphicsView as tbastian blogged about just recently: Videos get pimped
I've also embedded the 3d .obj model viewer I blogged about earlier (Accelerate your widgets with OpenGL) to show how to mix in OpenGL content by setting up the correct projection and modelview matrices. Note that except from this 3d model everything else is drawn using QPainter with QTransform, both the walls, sprites, and widgets.
Now, this example might not be the most useful thing in the world, but it's meant as a demonstration of how you can stretch the Qt API in new directions.
Note that the performance against Qt 4.5 is better than against Qt 4.4, so if you try it out you might want to use the 4.5 snapshots at the moment. For the very best performance run with the "-graphicssystem raster" option (So long and thanks for the blit!). Also, there seems to be some bugs regarding certain widgets not being shown on Windows/Mac. Left-clicking links in embedded QWebViews is also broken at the moment.