This is the top of the elevator, which is a piston door. “true” means removing grain effect of potion - different degrees present different effect, some specific degrees even shows particular effect. “levitation” is the NBT of floating effect, that number is alterable, and “20” means the floating effect lasts for 20 seconds while “10” means the degree of floating rate. “type=player” means only players are allowed to get floating effect, similarly, “type=Pig” means only pig is allowed to get the effect. “r=1” refers to the site that is one block away from yourself, similarly, r=100 means the site that is 100 block far away. “effect” means giving players two kinds of potion effects - to all entities - “x”, “y”, “z” refers to the three dimensional location of players, only at the location can players obtain potion effect if you haven’t added location by yourself, then the practical location is that of the command block.

Taking effect levitation 20 10 true for example But presumably the creators will continue to update the builds as they do more testing and fine tuning. That will give you access to the most current builds of OptiFine - as of the writing of this article, Alpha 2, Alpha 3, and Alpha 4 are available.

There two command blocks staying one side of the elevator, and the upper one is for floating effect. Go to the OptiFine downloads page and click the 'Preview Versions' link.

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