Implemented something like debris asteroid belt around a planet. Nothing new relative to engine, just few hundreds of asteroids orbiting a planet. Brute force implementation killed FPS immediately, so I made many optimizations: reduce size of asteroids to few kilometers (so only few models generated and rendered at once), disable lighting and casting shadows by asteroids on each other, make their orbits circular (so orbital motion computation is going as fast as possible). Anyway, FPS is just 30-40 if time is paused, and dropped twice if time is running (but this depend on planetary system - number of suns, asteroid belts, etc). However, lighting and shadowing is perfect.