[Interest] [Qt3D] Cylinder Mesh Mod Problem

[Andy]

> Subject: [Interest] [Qt3D] Cylinder Mesh Mod Problem
> I am trying to work with and understand the Qt3D geometry and mesh system.
>
> Based on Paul's answer to my earlier question I thought I'd start with
something simple: a cylinder without the end caps (QCylinderMesh always
includes them).
>
> I started by taking the QCylinderGeometry/QCylinderMesh code and making
it build outside of the Qt5 build system.  Next I removed the code for
adding the caps (called discs in the code).
>
> The cylinder looks good, but there seems to be an extra vert at (0.0,
0.0, 0.0) and faces created between it and the top ring.  I can't for the
life of me figure out where the extra vert is coming from or where those
faces are created.
>
> I put some example code and a couple of images here:
>
>    https://github.com/asmaloney/Qt3D-mesh-problem
>
> I am using the latest Qt 5.6 git from 22 Jan (SHA
1fcdb6cafcf7621fdea84e28a95934a4a04ea1b7) which uses Qt3D from 21 Jan (SHA
44c743c90cf51eddbf5b0bb3cf957c58fa0ef94f).
>
> Any ideas what I'm doing wrong or suggestions on how to figure it out?
>
> Thank you for any help/suggestions!
>
> - Andy

I've discovered the problem.  There is a bug in QCylinderGeometry's
calculation of the cylinder's side indices.  You can see it if you move the
camera "inside" a cylinder.  I put an example image here:

  https://github.com/asmaloney/Qt3D-mesh-problem

I fixed the example code in the repo.  Two small changes in
CylinderIndexDataFunctor::operator () and createSidesIndices() which should
be applied to Qt3D's QCylinderGeometry.

- Andy
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