How do I wake a sleeping RigidBody3D in Godot?

Set sleeping = false directly, or call apply_impulse with any nonzero force — apply_impulse automatically wakes the body. apply_force (continuous) only wakes if the force exceeds the wake threshold. For guaranteed wake, use apply_impulse(Vector3.ZERO + tiny_epsilon).

What is the difference between sleeping and can_sleep in Godot?

sleeping is the current runtime state: true = not simulated right now. can_sleep is a permission: true = PhysX may put this body to sleep when idle. Set can_sleep to false to prevent sleep entirely; set sleeping to false to wake a currently-sleeping body.

Does RigidBody3D contact_monitor affect sleep behavior?

Yes indirectly. contact_monitor enabled with max_contacts_reported > 0 keeps Godot tracking contacts for the body, which can wake it on new contacts. Without contact monitoring, a sleeping body may not wake when another body touches it as reliably.

Fix: Godot RigidBody3D Sleeping Not Waking

Quick answer: apply_force does not wake sleeping bodies unless above the wake threshold. Use apply_impulse to guarantee a wake, or explicitly set sleeping = false before applying force. can_sleep = false disables sleep entirely for bodies that need constant simulation.

Here is how to fix Godot RigidBody3D sleeping not waking. You drop a dynamic crate onto the ground. It settles and goes to sleep. You call apply_force on it to simulate wind or a repelling field — nothing happens. The force shows no effect, the body stays still, sleep wins. Godot’s physics sleep behavior mirrors Unity’s: efficient, correct, and infuriating when you do not know the rules.

The Symptom

A RigidBody3D that has come to rest stops responding to forces:

apply_force produces no motion
add_constant_force accumulates but body does not move
Small collisions from other sleeping bodies produce no response
sleeping property reads as true

Large forces (gravity change, explosion) do wake it. Rebuilding the scene or entering play mode starts the body awake until it settles again.

What Causes This

Force vs impulse semantics. apply_force adds continuous acceleration — small magnitudes accumulate over time. For sleeping bodies, Godot requires the force to exceed a wake threshold before the body wakes. apply_impulse applies instant velocity change; any non-zero impulse wakes the body immediately.

Sleep threshold in Project Settings. Project Settings > Physics > 3D > Sleep Threshold Linear and Angular Threshold. Default 0.1 m/s linear and ~0.1 rad/s angular. Forces that produce velocities below this get ignored as “too small to wake.”

Sleeping property stuck true. If code once set sleeping = true explicitly (pausing a body), it stays true until explicitly set false. Not uncommon during state restores from save data.

Contact monitor disabled. If contact_monitor = false or max_contacts_reported = 0, the body does not track collisions well enough for physics to wake it on touch. Other dynamic bodies colliding into it do wake it (PhysX handles that globally), but it is less reliable for edge cases.

The Fix

Step 1: Use apply_impulse for user-initiated forces. If your code says “this body should move now,” use apply_impulse. It always wakes the body and applies the velocity change in one frame.

extends RigidBody3D

func push_hard(direction: Vector3):
    # Impulse wakes the body automatically
    apply_impulse(direction * 5.0)

func apply_wind(direction: Vector3, delta: float):
    # Continuous force; wake manually first
    if sleeping:
        sleeping = false
    apply_force(direction * 2.0)

The pattern: impulse for one-shot events, force for continuous with an explicit wake. Never assume apply_force will wake a sleeping body.

Step 2: Disable sleep on critical bodies. For bodies that must always simulate (main characters, vehicles, things that move based on script), disable sleep:

func _ready():
    can_sleep = false

No CPU-saving benefit, but guaranteed responsiveness. Use sparingly — a scene with 200 always-awake rigidbodies costs much more than 200 normally-sleeping ones.

Step 3: Tune global thresholds. Project Settings > Physics > 3D. Lower values mean less aggressive sleep:

Sleep Threshold Linear: 0.05 (lower than default 0.1)
Sleep Threshold Angular: 0.05
Time Before Sleep: 0.5 s (lower = sleeps faster; raise to 1.0 s for more responsiveness)

These are global. For most games the defaults are fine; tweak only if your use case has many bodies that should respond to light forces.

Step 4: Enable contact monitoring where needed. If you want sleeping bodies to wake on touch and also react via signals:

func _ready():
    contact_monitor = true
    max_contacts_reported = 4
    body_entered.connect(_on_body_entered)

func _on_body_entered(body):
    sleeping = false
    # react to collision

Debugging

Visualize sleep state with a debug indicator:

func _process(_delta):
    $DebugLabel.text = "sleeping=" + str(sleeping)
    $DebugLabel.modulate = Color.GRAY if sleeping else Color.GREEN

Place a 3D label on bodies during dev. See which ones are asleep at any moment. Unexpected sleeps tell you where thresholds need tuning.

Performance Tradeoff

Sleep is a legitimate optimization — scenes with 1000 rigidbodies where only a few move at a time pay almost no cost for the 995 sleeping ones. Disabling sleep on everything or lowering thresholds too far costs CPU that scales with body count. Measure frame time before and after changing sleep settings on a realistic scene.

“Sleep is PhysX being considerate. When you need responsiveness, be explicit: impulse, not force; sleeping = false, not hope.”

Related Issues

For CharacterBody3D issues, see CharacterBody2D Floor Snap (same concepts in 3D). For area detection, Area2D Not Detecting StaticBody2D covers related physics issues.

Impulse for one-shot, force with explicit wake for continuous. Know when to use each.