optifine custom potions

speed.properties:

type=item
items=minecraft:potion
model=speed.json
nbt.display.Name=ipattern:*swiftness*
//the potion must be literally renamed to "swiftness", this is just an example anyways


speed.json:

{
    "parent": "builtin/generated",
    "textures": {
        "layer0": "mcpatcher/cit/blank",
        "layer1": "mcpatcher/cit/speed_potion"
    },
    "display": {
        "thirdperson": {
            "rotation": [ -90, 0, 0 ],
            "translation": [ 0, 1, -3 ],
            "scale": [ 0.55, 0.55, 0.55 ]
        },
        "firstperson": {
            "rotation": [ 0, -135, 25 ],
            "translation": [ 0, 4, 2 ],
            "scale": [ 1.7, 1.7, 1.7 ]
        }
    }
}
(mcpatcher/cit/blank is literally an empty 16x16 image to get rid of layer 0, since it will be tinted. layer 1 is the full, already-colored potion texture, same way as it'll look like in-game)