Improving Frame Rate with OptiFabric Without Losing Visuals

Start with the high-impact settings

Open Options → Video Settings. Reduce Render Distance first — it is the single largest performance lever. Next, lower Shadow Quality if shaders are active, and set Clouds to off or fast. Under Performance, enable Fast Render, Fast Math, and Smooth FPS, and set Chunk Updates to a lower value if you see stuttering when flying. Turn Dynamic Lights down or off if you are not relying on them.

Reduce entity and particle load

OptiFine can limit how much work entities and particles cause. Lower Particles to decreased or minimal, and reduce Entity Distance so distant mobs stop being fully processed. Turning off Fog can help too, since it removes an extra rendering pass.

Verify the result

Press F3 to watch your frame rate while you change one setting at a time, so you know which change actually helped. Test in a busy area — a village at night with mobs and torches is a better benchmark than an empty plains biome. If performance is still poor, disable shaders entirely and confirm the base game runs smoothly before re-enabling them, which tells you whether the bottleneck is OptiFine's shader pipeline or something else in your modpack.