All the polygons are being reprocessed for connections and re-rendering every frame, causing huge lag when lots are used. I recommend detecting when they have been placed and then caching it to improve performance drastically. Putting the data into a vertex buffer and only reprocessing it when they move or lighting changes happen would help a lot. A bit of a challenge to pull of but would benefit greatly!

VisualVM

Looking down the hall where all the garlands are, 30 fps:

Looking away from them, 90 fps: