unity-vrc-world-sdk-3

name	unity-vrc-world-sdk-3
description	VRChat World SDK 3 scene setup and optimization guide. Use this skill when configuring VRChat world scenes, placing SDK components, setting up layers, optimizing performance, or uploading worlds. Covers VRC_SceneDescriptor, spawn points, VRC_Pickup, VRC_Station, VRC_Mirror, VRC_ObjectSync, VRC_CameraDolly, layer/collision matrix, baked lighting, Quest/Android limits, and upload workflow. SDK 3.7.1 - 3.10.3 coverage. Triggers on: VRChat world, VRC SDK, scene setup, VRC_SceneDescriptor, spawn point, VRC_Pickup, VRC_Station, VRC_ObjectSync, layer setup, optimization, Quest support, light baking, upload, FPS improvement. Related: Use unity-vrc-udon-sharp for UdonSharp C# coding.
license	MIT
metadata	{"author":"niaka3dayo","version":"2.3.0","tags":"vrchat, world-sdk, scene-setup, optimization, components, upload"}

VRChat World SDK 3 Guide

Table of Contents

Section	Content	Reference
Scene Setup	VRC_SceneDescriptor, Spawn	This file
Components	Pickup, Station, Mirror	references/components.md
Layers & Collision	Layers, Collision Matrix	references/layers.md
Performance	Optimization guide	references/performance.md
Lighting	Lighting settings	references/lighting.md
Audio & Video	Audio, Video players	references/audio-video.md
World Upload	Upload workflow	references/upload.md
Troubleshooting	Problem solving	references/troubleshooting.md
Cheatsheet	Quick reference	CHEATSHEET.md

---

Common Mistakes (NEVER List)

These cause silent world failures, performance disasters, or Quest incompatibility:

#	NEVER do this	Why it hurts	Use instead
1	Enable Mirror by default (active on world join)	Renders the entire scene twice — immediate FPS halving, catastrophic on Quest	Default Mirror OFF; add UdonSharp toggle or player-triggered activation
2	Use realtime directional lights with real-time shadows	Quest has no hardware shadow acceleration; each shadow caster costs 10-30 FPS	Baked lightmaps + light probes; set lights to Baked or Mixed mode
3	Set Respawn Height at or above the world floor	Player respawns → falls → respawns again → infinite loop; players cannot recover	Set to an unreachable depth (e.g., floor at Y=0 → Respawn at Y=-100)
4	Skip "Setup Layers for VRChat" on a new project	Layer collision matrix is wrong by default — players walk through walls, Pickups clip floors	Run VRChat SDK > Builder > "Setup Layers for VRChat" before placing any colliders
5	Enable Post-Processing without Quest build profile	Post-Processing is silently disabled at runtime on Quest but VRAM is still allocated	Use separate Android build profile or guard assets with #if UNITY_ANDROID
6	Place more than 2 active video players simultaneously	Each player adds significant decoding overhead; running >2 simultaneously is a common cause of frame drops and audio issues in practice	Disable extra players at scene start; activate only the currently playing one
7	Use Unity Constraints or Cloth on Quest	Both are disabled silently at runtime on Quest — animations freeze, cloth hangs in place	Use Animator-driven transforms (no constraints) or remove cloth from Quest meshes
8	Upload without completing a lightmap bake	Realtime GI calculates at runtime — 3-5× draw call overhead, unacceptable on Quest	Always bake lights before upload; Progressive GPU lightmapper is fastest
9	Place player walkable surfaces on Default layer (0)	Collision matrix is wrong by default — avatar physics collision is unreliable; players may clip through geometry	Use Environment (layer 11) for all walkable geometry, walls, and floors
10	Use very high lightmap resolution for large areas without profiling	Texture memory can spike significantly at high resolutions; a common cause of OOM crashes on mobile headsets	Start at 10-20 texels/unit as a practical guideline; profile VRAM and adjust — official guidance says "keep lightmap resolution low" for Quest
11	Add VRC_UIShape to a Screen Space or Overlay Canvas	VRC_UIShape requires World Space Canvas; other modes throw a runtime Unity error in VRChat — the UI renders visually but is not interactive, with no visible error to the world builder	Set Canvas > Render Mode to World Space before adding VRC_UIShape

Reference Loading Guide

Load only what the task requires.

Task	MANDATORY READ	Optional	Do NOT Load	Load Rationale
Setting up a new scene from scratch	components.md, layers.md	upload.md	audio-video.md, troubleshooting.md	Collision matrix non-obvious; component deps needed upfront
Making objects grabbable (VRC_Pickup)	components.md	layers.md	audio-video.md, lighting.md	Pickup/Rigidbody requirements not in standard Unity docs
Setting up seating (VRC_Station)	components.md	layers.md	audio-video.md, performance.md	Station collider + exit requirements are VRChat-specific
Optimizing FPS for Quest	performance.md, lighting.md	troubleshooting.md	audio-video.md, upload.md	Quest limits differ from PC; bake requirements non-obvious
Adding audio or video player	audio-video.md, components.md	troubleshooting.md	lighting.md, performance.md	AVPro vs Unity Video selection is VRChat-specific
Baking lights / lightmap setup	lighting.md, performance.md	—	audio-video.md, layers.md	Lightmap resolution and probe placement affect Quest VRAM
World upload and publish	upload.md	troubleshooting.md	audio-video.md, lighting.md	Upload steps and validation order are fragile; easy to miss
Debugging collision or layer issues	layers.md, troubleshooting.md	components.md	audio-video.md, lighting.md	VRChat collision matrix differs from Unity default
Mirror setup and configuration	components.md	performance.md	audio-video.md, upload.md	Mirror layer mask requirements are VRChat-specific

Before Starting a New World — Design Decisions

These decisions shape every downstream choice. Make them first, before placing any component.

Decision	Options	Implication
Quest required?	Yes / No	Yes → Quest First philosophy applies from day 0, not as a retrofit
Expected player count?	1–8 / 9–40 / 40+	Affects spawn count, mirror policy, max video players
Primary interaction?	Grab (Pickup) / Sit (Station) / Watch (Video) / Explore	Determines which SDK components are mandatory
Lighting approach?	Baked / Mixed / Realtime	Realtime is only viable on PC-only worlds; all lights must be baked before upload
Networked objects?	None / Physics (Pickup+ObjectSync) / State (UdonSynced)	Determines sync architecture before Udon scripting begins

---

Design Philosophy: Quest First

Build for Quest and get PC for free. Build for PC and Quest becomes a separate project.

Quest (Meta Quest 2/3/Pro) defines the performance budget:

• CPU/GPU: ~2× slower than PC VR; tile-based GPU with no hardware shadow maps
• VRAM: ~4 GB shared with OS (vs 6–12 GB on PC); no HDR framebuffer
• Thermal throttling: Sustained 100% GPU load causes clock reduction within minutes

If a world runs at 72 FPS on Quest with a single test client, it will typically run at 90+ FPS on PC — though results vary by shader complexity, CPU-bound workloads, and hardware differences. The converse rarely holds. Verify against the official VRChat optimization documentation before publishing.

NEVER optimize exclusively for PC with "Quest support added later" — by that point, lighting, materials, and mesh density are all locked to PC quality, and the Quest port requires rebuilding everything.

Quest First Cascade — when Quest is required, every downstream decision inherits constraints:

Quest required? → Yes
  ├── Shaders: Mobile-only (Standard Lite, Toon Lit)
  ├── Lighting: Fully baked (no realtime shadows)
  ├── Geometry: 50K-100K triangles (target range)
  ├── Materials: < 25 unique materials
  ├── Audio: Mono, compressed, limited concurrent sources
  └── Physics: Simplified colliders, minimal Rigidbodies

SDK Versions

Supported versions: SDK 3.7.1 - 3.10.3

SDK	New Features	Status
3.7.1	StringBuilder, Regex, System.Random	✅
3.7.4	Persistence API (PlayerData/PlayerObject)	✅
3.7.6	Multi-platform Build & Publish (simultaneous PC + Android builds)	✅
3.8.0	PhysBone dependency sorting, Force Kinematic On Remote, Drone API	✅
3.8.1	[NetworkCallable] events with parameters, Others/Self targets	✅
3.9.0	Camera Dolly API, Auto Hold simplification, VRCCameraSettings	✅
3.10.0	Dynamics for Worlds (PhysBones, Contacts, VRC Constraints)	✅
3.10.1	Bug fixes and stability improvements	✅
3.10.2	EventTiming extensions, PhysBones fixes, shader time globals	✅
3.10.3	VRCPlayerApi.isVRCPlus, VRCRaycast (avatar), Mirror render-order fix	✅ Latest stable

Important: SDK versions below 3.9.0 are deprecated as of December 2, 2025. New world uploads are no longer possible with these versions.

---

Scene Setup

VRC_SceneDescriptor (Required)

Exactly one is required in every VRChat world.

[VRCWorld Prefab]
├── VRC_SceneDescriptor (Required)
├── VRC_PipelineManager (Auto-added)
├── VRCWorldSettings (Optional - movement speed settings)
└── AvatarScalingSettings (Optional - avatar scale limits)

All Properties

Property	Type	Description	Default
Spawns	Transform[]	Array of spawn points	Descriptor position
Spawn Order	enum	Sequential/Random/Demo (Demo: all players to Spawns[0])	Sequential
Respawn Height	float	Respawn height (Y axis)	-100
Object Behaviour At Respawn	enum	Respawn/Destroy	Respawn
Reference Camera	Camera	Player camera settings reference	None
Forbid User Portals	bool	Disable user portals	false
Voice Falloff Range	float	Voice attenuation range	-
Interact Passthrough	LayerMask	Interact passthrough layers	Nothing
Maximum Capacity	int	Max player count (hard limit)	-
Recommended Capacity	int	Recommended player count (UI)	-

Reference Camera Usage

// Usage:
// 1. Adjust Near/Far clipping (recommended for VR: 0.01 ~ 1000)
// 2. Apply Post Processing effects
// 3. Set background color

// ⚠️ MUST disable the Camera component after configuring — an active Reference Camera
//    renders a second viewport. VRChat reads only the camera settings, not its output.
// Assign the configured (disabled) Camera to VRC_SceneDescriptor > Reference Camera.

Spawn Points Setup

// Spawn points are empty GameObjects assigned to VRC_SceneDescriptor > Spawns array.
// Players enter facing the Z+ direction of the spawn Transform.

// VRChat-specific requirements:
// - At least 2-3 spawn points (for simultaneous joins — single spawn causes overlap)
// - Place slightly above the floor (~0.1m) to avoid floor collision on spawn
// - Keep clear of obstacles (VR player guardian area is larger than their avatar)
// - Account for VR guardian boundaries — desktop player sizes differ from VR

Required Setup Checklist

□ Exactly one VRCWorld Prefab exists in the scene
□ At least one Transform set in Spawns
□ Respawn Height set to an appropriate value (well below the floor)
□ Reference Camera configured for clipping distances (for VR)
□ Layer/Collision Matrix correctly configured
□ "Setup Layers for VRChat" has been executed

---

Components

MANDATORY READ references/components.md (~800 lines) before configuring any VRC component below. Load in full — dependency requirements and Udon event hooks are distributed throughout. Do NOT Load: references/audio-video.md, references/lighting.md.

Component	Required Elements	Purpose	SDK
VRC_SceneDescriptor	-	World settings (required)	-
VRC_Pickup	Collider + Rigidbody	Grabbable objects	-
VRC_Station	Collider	Sittable locations	-
VRC_ObjectSync	Rigidbody	Auto-sync Transform/physics	-
VRC_MirrorReflection	-	Mirror (⚠️ high cost)	-
VRC_PortalMarker	-	Portal to other worlds	-
VRC_SpatialAudioSource	AudioSource	3D audio	-
VRC_UIShape	Canvas (World Space)	Unity UI interaction	-
VRC_AvatarPedestal	-	Avatar display/switch	-
VRC_CameraDolly	-	Camera dolly	3.9+

VRC_ObjectSync vs UdonSynced

Scenario	VRC_ObjectSync	UdonSynced variables
Throwable objects / physics	✅ Recommended	❌
State only / complex logic	❌	✅ Recommended

SDK 3.8.0+: Force Kinematic On Remote — Makes Rigidbody kinematic on non-owner clients, preventing unexpected physics behavior.

---

Layers & Collision

VRChat Reserved Layers

Layer #	Name	Purpose
0	Default	General objects
9	Player	Remote players
10	PlayerLocal	Local player
11	Environment	Environment (walls, floors)
13	Pickup	Grabbable objects
14	PickupNoEnvironment	Pickups that don't collide with environment
17	Walkthrough	Walk-through objects
18	MirrorReflection	Mirror reflection only
22-31	User Layers	Available for custom use

Layer Setup Steps

1. VRChat SDK > Show Control Panel
2. Builder tab
3. Click "Setup Layers for VRChat"
4. Collision Matrix is automatically configured

MANDATORY READ references/layers.md when setting up collision or debugging physics. The default Unity collision matrix differs from the VRChat-correct one — always verify. Do NOT Load: references/audio-video.md, references/upload.md.

---

Performance

Target FPS

Platform	FPS Target	Measurement Point
PC VR	45+ FPS	Spawn point, 1 player
PC Desktop	60+ FPS	Spawn point, 1 player
Quest	72 FPS	Spawn point, 1 player

Critical Limits

Item	Recommended	Reason
Mirrors	1, default OFF	Renders the entire scene 2x
Video players	Max 2	Decoding overhead
Realtime lights	0-1	Dynamic shadows are expensive
Lightmaps	Required	Performance foundation

Quest/Android Restrictions

Component	PC	Quest
Dynamic Bones	✅	❌ Disabled
Cloth	✅	❌ Disabled
Post-Processing	✅	❌ Disabled
Unity Constraints	✅	❌ Disabled
Realtime lights	✅	⚠️ Avoid

Performance Optimization Workflow

Bottleneck Type	Key Indicators	Reference
CPU-bound	High script time, physics overhead	performance.md §Optimization-Workflow
GPU-bound	Draw calls, overdraw, shader complexity	performance.md §Optimization-Workflow
Memory	VRAM usage, texture size, mesh count	performance.md §Optimization-Workflow

MANDATORY READ: Load performance.md before optimizing — measure first, then target the largest bottleneck.

MANDATORY READ references/performance.md and references/lighting.md for Quest optimization. Do NOT Load: references/audio-video.md, references/upload.md.

---

Lighting

Baked Lighting (Required)

✅ Recommended settings:
├── Lightmapper: Progressive GPU
├── Lightmap Resolution: 10-20 texels/unit
├── Light Mode: Baked or Mixed
└── Light Probes: Place along player paths

❌ Avoid:
├── Realtime lights (dynamic shadows)
├── High-resolution lightmaps (memory consumption)
└── Excessive Reflection Probes

MANDATORY READ references/lighting.md when configuring lightmaps or light probe placement. Do NOT Load: references/audio-video.md, references/upload.md, references/layers.md.

---

Audio & Video

VRC_SpatialAudioSource

Property	Description	Default
Gain	Volume (dB)	0 (World: +10)
Near	Attenuation start	0m
Far	Attenuation end	40m
Volumetric Radius	Source spread	0m
Enable Spatialization	3D positioning	true

Video Player Selection

Feature	AVPro	Unity Video
Live streaming	✅	❌
Editor preview	❌	✅
YouTube/Twitch	✅	❌
Quest support	✅	✅

MANDATORY READ references/audio-video.md for VRC_SpatialAudioSource or video player configuration. Do NOT Load: references/lighting.md, references/performance.md.

---

World Upload

Upload Steps

1. Check Validation
   └── VRChat SDK > Build Panel > Validations

2. Build & Test (local testing)
   └── "Build & Test New Build"
   └── Supports multi-client testing

3. Upload
   └── "Build and Upload"
   └── Set Content Warnings
   └── Set Capacity

4. Publish settings
   └── Configure public/private on the VRChat website

Pre-Upload Checklist

□ VRC_SceneDescriptor × 1
□ Spawns configured
□ Respawn Height appropriate
□ Layer/Collision Matrix verified
□ Light baking complete
□ Mirror default OFF
□ 45+ FPS in VR
□ No Validation errors
□ Content Warnings set
□ Capacity set

MANDATORY READ references/upload.md before running Build & Upload. Verify all pre-upload checklist items first. Do NOT Load: references/audio-video.md, references/lighting.md.

---

Troubleshooting

Quick Router

Identify the symptom category and jump to the reference section:

Symptom Category	Common Cause	Reference
Player walks through walls / floor	Layer setup not run; geometry not on Environment (11)	troubleshooting.md §Layer & Collision
Can't grab / Pickup not working	Missing Collider, Rigidbody, or VRC_Pickup component	troubleshooting.md §Component
Object not syncing / snaps back	Missing VRC_ObjectSync or ownership not transferred	troubleshooting.md §Networking
Can't sit / clips through Station	Missing Collider; Station Collision Transform needs adjustment	troubleshooting.md §Component
Mirror not reflecting	Layers mask missing Player/PlayerLocal/MirrorReflection	troubleshooting.md §Component
Build / Upload fails	Missing SceneDescriptor, script errors, layer warnings	troubleshooting.md §Build
Performance issues	Mirror ON, realtime lights, uncooked lightmaps	performance.md
Works in Editor but fails in VRChat	Editor Play ≠ SDK runtime; use Build & Test	troubleshooting.md §Editor
UI visible but not clickable	VRC_UIShape on Screen Space / Overlay Canvas (see NEVER #11)	troubleshooting.md §Editor

MANDATORY READ references/troubleshooting.md when diagnosing any issue. Do NOT Load for non-troubleshooting tasks.

---

Related Skills

For C# scripting, network sync, and UdonSharp event implementation, use the unity-vrc-udon-sharp skill.

---

Templates (assets/templates/)

Starter templates for common SDK component patterns. Each template compiles without modification; adjust Inspector fields and extend the event stubs for your world.

Template	Purpose
VRC_Pickup_Rigidbody.cs	VRC_Pickup with Rigidbody — OnPickup/OnDrop/OnPickupUseDown/OnPickupUseUp events, ownership transfer, audio feedback
VRC_Station_Basic.cs	VRC_Station controller — OnStationEntered/OnStationExited events, PlayerMobility, force-eject API

References

File	Content	Approx. Lines
references/components.md	All component details	800+
references/layers.md	Layers & collision	400+
references/performance.md	Performance optimization	500+
references/lighting.md	Lighting settings	400+
references/audio-video.md	Audio & video	400+
references/upload.md	Upload procedure	300+
references/troubleshooting.md	Troubleshooting guide	500+
CHEATSHEET.md	Quick reference	200+