[Development] Qt3D questions and wishes

Harald Vistnes harald.vistnes at gmail.com
Mon Aug 10 07:35:37 CEST 2015


I have played with the tech preview of Qt3D 2.0 and I have some questions
and wishes.

1. Transparency. It does not seem like Qt3D handles transparency at all.
For instance, phong.frag always returns alpha=1.0. I would expect materials
like Qt3D::QPhongMaterial to have an opacity parameter and that the
renderer would first render opaque meshes and then transparent meshes
sorted by depth. Ideally I would love to have support for OIT out of the
box, but that may be too specialized. Will there be any support for
transparent materials in the upcoming release?

2. Shared vertex buffers. How can multiple meshes share the same vertex

3. Updating vertex buffers. How can one update the vertices of an existing
mesh? Qt3D::QAbstractMesh only expose the meshFunctor() function, so I
don't see how to update an existing mesh with new vertex data.

4. Text. It would be nice with an example showing how to add text to a Qt3D
scene. Both 2D (specified in screen coordinates) and 3D (specified in world
coordinates). I'm only using C++, so that is what is of interest to me.

5. It would be nice to have a class like QTriangleMesh out of the box where
the user can specify his own vertices, normals, indices, etc. I implemented
such a class following the pattern of the Qt3D::QCylinderMesh
implementation, but ended up with a copy of the vertex/index arrays in both
the TriangleMeshPrivate and TriangleMeshFunctor class before they were
actually used in the Qt3D::QAbstractMeshFunctor::operator()(). Is there a
better way to handle this, to avoid all those copies of the data?

6. Polygon offset to handle z-fighting.

7. All examples in C++. In the tech preview, many of the examples were QML

Thanks. I'm looking forward to see the progress in the next release!

Best regards
Harald Vistnes
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