Is your codepath hitting the addActor lines when you right click? It could be that the spheres are tiny; the radius is set to 0.01.
The radius is fine, also tried something bigger like 0.10. it works for a simple vtk appxn
Yes it does hit the
addActor line as shown in the console.
The only other thing I can think of to debug this is to log the actors in the scene after clicking. Either the actor isn’t getting added or some other code is removing the spheres.