Q3DSurface selected point signal

let-robots-reig

I am using QtDataVisualization (Q3DSurface in particular) to make a simple 3D surface graph.

The Q3DSurface supports selection of a point on the graph by showing a highlighted ball on the data point where the user has clicked. The selection pointer shows the coordinates of the point. It looks like this: surface with selected point

However, I'm not able to find a signal that is emitted when the selection happens. Having read through the documentation of Q3DSurface and QSurface3DSeries, I failed to find any corresponding signal. There is only a selectedPointChanged(const QPoint &position) in QSurface3DSeries, but it operates with a two-dimensional QPoint which is not suitable for the case.

What I am trying to do is store a history of selected points, that is why I need such a signal to keep track of previous coordinates. I tried looking into implementing a custom Q3DInputHandler, but not sure that it can resolve the issue. I would be grateful for any advice on the solution.

Henrik Thoma

Although this topic is quite old, you were on the right track. The selectedPointChanged(const QPoint &position) signal provides the position of the selected point in your QtDataVisualization::QSurfaceDataProxy, which can be used to access the desired information by using QtDataVisualization::QSurfaceDataProxy::itemAt(const QPoint &position). Below a minimalistic outline of the basic steps:

using namespace QtDataVisualization;
...

# surface init (should already exist)
Q3DSurface *surfacePlot = new Q3DSurface();
QSurfaceDataProxy *surfaceDataProxy = new QSurfaceDataProxy();
QSurface3DSeries *surfaceDataSeries = new QSurface3DSeries(surfaceDataProxy);
surfacePlot->addSeries(surfaceDataSeries);

# connect the selectedPointChanged signal to e.g. your desired foo function
# (adjust this to fit the required signal/slot type for your function)
QObject::connect(surfaceDataSeries, &QSurface3DSeries::selectedPointChanged, foo);

# the foo funciton should look like
void foo(const QPoint &position)
{
    if ((position.x() < 0) or (position.y() < 0))
        return; // nothing selected
    QVector3D pos = surfaceDataProxy->itemAt(position)->position(); // (x,y,z) data for selected point
    ... # e.g. store the pos in some list
}