| name | roblox-physics |
| description | Use when building Roblox vehicles, ragdolls, projectiles, elevators, constraints, forces, or other physics-driven gameplay. |
| last_reviewed | "2026-07-13T00:00:00.000Z" |
| sources | ["https://raw.githubusercontent.com/Roblox/creator-docs/main/content/en-us/physics/mechanical-constraints.md","https://raw.githubusercontent.com/Roblox/creator-docs/main/content/en-us/physics/mover-constraints.md","https://create.roblox.com/docs/projects/server-authority"] |
When to Load
Use this skill when building physics-driven gameplay: vehicles, ragdolls, projectiles, mechanical contraptions, elevators, swinging platforms, or anything using constraints and forces.
Quick Reference
Constraint Types
Mechanical: HingeConstraint, PrismaticConstraint, CylindricalConstraint, BallSocketConstraint, UniversalConstraint, WeldConstraint/RigidConstraint
Motion: AlignPosition, AlignOrientation, LinearVelocity, AngularVelocity, VectorForce, Torque
Spring/Rope: SpringConstraint, RopeConstraint, RodConstraint
Attachment Pattern
Constraints connect via Attachment objects. Create one on each part, set Attachment0/Attachment1, and parent the constraint to part0. Actuator types include None, Motor, and Servo.
Vehicles
Vehicles: use motorized HingeConstraint wheels, SpringConstraint suspension, servo steering, and CustomPhysicalProperties for friction tuning.
Ragdoll
Replace Motor6Ds with BallSocketConstraint: create Attachments from motor.C0/C1, set LimitsEnabled=true, UpperAngle=45. Keep Root Motor6D for HRP. Set humanoid state to Physics. Re-enable motors to recover.
Authority and Network Ownership
Classic projects: automatic ownership can give an unanchored assembly to a nearby player. SetNetworkOwner(nil) keeps it server-owned; SetNetworkOwner(player) gives a player simulation ownership. Treat player-owned physics as untrusted and validate gameplay outcomes.
Server Authority: set Workspace.AuthorityMode = Server with its required settings. Core objects can remain server-owned while prediction keeps controls responsive, so the classic secure-but-laggy trade-off does not apply. SetNetworkOwner() is not a substitute.
Rule: choose the model first. Keep NPC and gameplay-critical objects authoritative; give client ownership to non-critical physics only when the resulting behavior is acceptable and tested.
Common Gotchas
- Constraints do nothing on Anchored parts
- Both Attachment0 AND Attachment1 required (missing one = silent fail)
- Over-constraining = jitter. Tune mass with
CustomPhysicalProperties
- Use Raycast for hitscan,
Touched only for slow physics projectiles
- Always set lifetime on physics projectiles (forgotten ones kill perf)
Need more detail? Load
references/full.md for the complete reference with code examples, API tables, and edge cases.
