Roblox physics

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.