Why does ShapeCast3D miss a thin colliding plane?

Plane shapes have zero thickness; cast may sample either side. Replace with a thin BoxShape3D (e.g. 0.05 unit deep). Or increase ShapeCast3D's margin to absorb the thinness.

ShapeCast3D's margin (collision_margin via PhysicsServer) extends the cast volume. Bumping to 0.1 grows the swept shape and catches thin obstacles.

Higher physics tick rate reduces the per-step distance, making thin obstacles less likely to be tunneled. 60 default; raise to 120 for fast-moving casters.

Fix: Godot ShapeCast3D Misses Thin Plane

Quick answer: Replace WorldBoundaryShape3D with a thin BoxShape3D (depth 0.05). Or raise ShapeCast3D margin.

Floor is a WorldBoundaryShape3D. Player ShapeCast3D down to detect ground. Half the time it misses.

The Fix

StaticBody3D <Floor>:
  CollisionShape3D:
    Shape:    BoxShape3D
    Size:     (100, 0.1, 100)   # thin but non-zero

ShapeCast3D <GroundProbe>:
  Shape:        BoxShape3D (0.5, 0.05, 0.5)
  Margin:       0.05
  Target Position: Vector3(0, -1.1, 0)

Box geometry is reliable for ground checks. Margin grows the sweep. Together they consistently report ground hits.

Verifying

Player walks; ground probe always returns true. Without box: intermittent miss.

“Box, not plane. Margin generous. Hits land.”

Related Issues

For Area2D fast mover, see CCD. For RigidBody3D damp, see damp.

Box. Margin. Cast hits.