I added the “ClearInstances” call before adding the instances, and suddenly the framerates are up around 70 fps.
Now i can remove the “ClearInstnaces” call and still have 70 fps. Obviously there must have been tons of instances lurking in the background.
Problem solved, but I am not completely comfortable that I can’t reproduce it.
[EDIT:] I am able to reproduce it!
While fidelling around i found that have removed the PointLights i had in the first example, and when i placed a couple of point lights over the tiles the framerates dropped very low again.
I turns out that if i have a few point ligths in the scene the rendering with Static Meshes is more effective, but if one only use directional light the instanced meshes are more effective. How can that be? (The point lights are set to stationary)