Why do bullets pass through walls in Godot?

Discrete physics integrates position once per tick. A fast body may move past a thin wall between steps. Set continuous_cd = true on the RigidBody to enable continuous collision detection (sweep test).

Should I just make walls thicker?

Pragmatic and effective. Walls thicker than (max body speed * physics tick) won't be tunneled. For 60Hz physics and 50 m/s bullets, walls need to be at least 0.85m thick to be safe.

CharacterBody3D has safe_margin: a small offset where collisions are pre-resolved. Larger margin = less tunneling at the cost of slight detachment from surfaces. Default 0.001 is fine for normal speeds.

Fix: Godot 4 Thin Collider Tunneled by Fast Body

Quick answer: Set continuous_cd = true on the fast RigidBody. Or thicken the thin wall to be wider than (max_speed * physics_tick). For CharacterBody3D, increase safe_margin.

Bullets pass through walls. The wall is 0.1m thick; the bullet moves 1m per physics tick. Bullet starts on one side of the wall and ends on the other; collision missed.

The Symptom

Fast objects pass through thin colliders. Slow speeds collide normally. Reproduces consistently above some speed threshold.

The Fix

Continuous CD on the bullet.

extends RigidBody3D

func _ready() -> void:
    continuous_cd = true   # sweep test against thin objects

Continuous CD performs a sweep test from previous to current position. Catches the wall regardless of thickness.

Or thicken walls. Cheap. Reliable. Limit max body speed to (wall_thickness / tick_seconds) and you don’t need continuous CD.

Or raycast bullet logic. For very-fast projectiles (laser, hitscan), don’t simulate physics — raycast each tick from old to new position and apply damage / spawn impact at the hit.

CharacterBody3D safe_margin

extends CharacterBody3D

func _ready() -> void:
    safe_margin = 0.05   # cm-scale margin

Resolves penetration before move_and_slide. Reduces tunneling without continuous CD.

Verifying

Test with a fast projectile and thin wall. Without fix: passes. With continuous_cd or thick wall: collides reliably.

“Continuous CD on fast bodies. Or raycast hitscan. Or thicker walls.”

Related Issues

For physics interpolation jitter, see interpolation. For PhysicsServer3D direct state, see direct state.

Sweep or thicken. Tunneling stops.