# Roblox Physics

> Use when building Roblox vehicles, ragdolls, projectiles, elevators, constraints, forces, or other physics-driven gameplay.

- Skill: `tabooharmony/roblox-physics` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tabooharmony/roblox-physics`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tabooharmony/roblox-physics/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tabooharmony (https://skillmd.com/u/tabooharmony)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/tabooharmony/roblox-physics

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# 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`. On recovery, destroy only the instances ragdoll created and restore only the motors it disabled (track both at enable time).

### 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.