Simple example of displaying a point in Qt3D

[daffmeister]

I'm porting an application based on Qt3D v.1 to Qt3D v.2 (Qt5.7).

As a very simple starting place I just need to display a bunch of points (ideally with colour and size). Are there any examples of such a simple application?

Thanks, Dave.

[koahnig]

@daffmeister

Hi and welcome to devnet forum

Would this be sufficient Qt3D examples?

[daffmeister]

Thanks @koahnig,

I've looked at the examples but they implement meshes with material properties, which I think is too heavy for what I need (ultimately a point cloud with 100,000's of points, so a sphere with fancy shading isn't going to work).

[koahnig]

@daffmeister

You would have to "thin out" one of the examples I guess. At least that would be my approach. Unfortunately I am not in QML and useless there.

[daffmeister]

Hi @koahnig,

That's what I've done so far, giving me this fragment:

Qt3DCore::QEntity *createScene()
{
    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;
    Qt3DRender::QMaterial *material = new Qt3DExtras::QPhongMaterial(rootEntity);
    Qt3DCore::QEntity *sphereEntity = new Qt3DCore::QEntity(rootEntity);
    Qt3DExtras::QSphereMesh *sphereMesh = new Qt3DExtras::QSphereMesh;
    ...
    (set sphereMesh properties)
    ...
    sphereEntity->addComponent(sphereMesh);
    sphereEntity->addComponent(material);
    }
    return rootEntity;
}

which I then view. That only scales to about a thousand points though before it starts slowing down (not surprising since it's rendering actual spheres). So I need simpler primitives.

[koahnig]

@daffmeister

I will mark this post and call for moderation. Someone else should be of more use here.

[Dabulla]

Hello,

I created a Qt3DPointcloudRenderer https://github.com/MASKOR/Qt3DPointcloudRenderer

It can render Pointcloud Library PCLPointcloud2.

If you already have your Vertexbuffer ready, you can simply use

GeometryRenderer {
    geometry: (...)
    primitiveType: GeometryRenderer.Points
}

and RenderState

StateSet {
    renderStates: [
        PointSize { specification: PointSize.Programmable },
        (...)
    ]
}

(PointSize seems to be broken in Qt version 5.7. The Application might crash on exit.)

[A Former User]

@Dabulla Hi! Would be great if you'd file a bug report for this PointSize RenderState issue. Thank you :)