Particles and transparent surfaces write no reliable depth or motion vectors, so FSR3's temporal history smears them into ghost trails while the opaque scene stays crisp. The fix is a reactive mask: this demo renders the transparents' coverage into a render-res mask and hands it to FSR3, so those pixels favour the current frame instead of trailing. Toggle reactive mask off to bring the trails back, and the Reactivity / Accumulation age debug views to see the mechanism.