Prediction

prediction is client.prediction(). It simulates the local player forward on a shadow entity that copies the player's movement attributes, and it simulates projectile flight from the last sent position.

on<Render3DEvent> { e ->
    val fall = prediction.path(10) { it.onGround() }   // stops on the first grounded tick
    val landing = fall.last().position()
    e.render().box(Box.around(landing, 0.2), Colors.RED, true)
}

Simulating movement

Method Type Description
prediction.after(ticks) PredictionResult state after ticks simulated ticks, live keyboard input
prediction.after(ticks, input) PredictionResult same, with input held for every simulated tick
prediction.path(ticks) List<PredictionResult> one immutable entry per simulated tick, tick 0 excluded
prediction.path(ticks, input) List<PredictionResult> same, with a fixed input
prediction.path(ticks, until) List<PredictionResult> stops after the first entry matching until, that entry included
prediction.path(ticks, input, until) List<PredictionResult> fixed input plus stop predicate

ticks is 1..100 on every method; movement runs on a shadow entity copying movement speed, sneak speed, jump strength, gravity, step height and movement efficiency. All six need a world and the client thread (main thread only); an out-of-range ticks throws ScriptException, a call from inside a path predicate throws ScriptStateException.

One simulated tick

Method Type Description
result.position() Vec predicted feet position in world blocks
result.velocity() Vec predicted velocity in blocks per tick
result.box() Box predicted bounding box in world coordinates
result.onGround() boolean predicted on-ground flag
result.inWater() boolean predicted touching-water flag
result.sneaking() boolean sneak state used for this tick
result.sprinting() boolean sprint state used for this tick
result.jumping() boolean jump input used for this tick
result.fallDistanceBlocks() double accumulated fall distance in blocks

The input

Method Type Description
moveInput(forward, backward, left, right, jump, sneak, sprint) MoveInput builds the input record, every argument defaults to false
MoveInput.NONE MoveInput all seven flags false
input.forward() boolean forward key held
input.backward() boolean backward key held
input.left() boolean strafe-left key held
input.right() boolean strafe-right key held
input.jump() boolean jump key held
input.sneak() boolean sneak key held
input.sprint() boolean sprint key held
input.copy(forward, backward, left, right, jump, sneak, sprint) MoveInput copy with named overrides, defaults read from the receiver

MoveInputEvent.toInput() returns the keys currently held — see Event list.

Projectiles

Method Type Description
prediction.projectile(kind) ProjectilePath trajectory on the last sent rotation, kind's default power
prediction.projectile(kind, aim) ProjectilePath aim null means the last sent rotation, kind's default power
prediction.projectile(kind, aim, power) ProjectilePath explicit launch power
path.points() List<Vec> trajectory positions, one per tick, from the launch point
path.lands() boolean a block or entity hit was found
path.landingPosition() Vec? position of the hit, null when nothing was hit
path.hitEntity() Entity? entity struck at the landing point, else null
path.hitsBlock() boolean the landing hit is a block
path.flightTicks() int points().size() - 1, minimum 0

Origin is the last sent position plus eye height, the launch velocity includes the player's current movement, and aim is a Rotation. All three need a world and the client thread (main thread only); a null kind or power at or below 0 throws ScriptException.

ProjectileKind

Constant Description
ARROW arrow physics, default power 3.0
TRIDENT trident physics, default power 2.5
ENDER_PEARL ender pearl physics, default power 1.5
SPLASH_POTION splash potion physics, default power 0.5, aim pitch -20°
SNOWBALL snowball physics, default power 1.5
WIND_CHARGE wind charge physics, default power 1.5

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