Specification
- Skill ID
- niaka3dayo/agent-skills-vrc-udon/unity-vrc-world-sdk-3
- Publisher
- niaka3dayo
- Repository
- agent-skills-vrc-udon
- Installs
- 0
- Files
- 13
- License
- MIT
- Synced
- Sep 23, 2026
How to use it
Open any RiverX project, open the Skills panel in the chat, and search for this identifier. The files are fetched from the source repository at install time.
niaka3dayo/agent-skills-vrc-udon/unity-vrc-world-sdk-3Installs these files- CHEATSHEET.md
- LICENSE.txt
- SKILL.md
- assets/templates/VRC_Pickup_Rigidbody.cs
- assets/templates/VRC_Station_Basic.cs
- references/audio-video.md
- references/build-validation.md
- references/components.md
- references/layers.md
- references/lighting.md
- references/performance.md
- references/troubleshooting.md
- references/upload.md
What this skill tells the agent
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 |
| Build Validation | Red/yellow/white SDK alerts | references/build-validation.md |
| World Upload | Upload workflow | references/upload.md |
| Troubleshooting | Problem solving | references/troubleshooting.md |
| Cheatsheet | Quick reference | CHEATSHEET.md |
Method Migration
The following public methods were renamed because an unprefixed, parameterless public UdonSharp method remains callable through legacy network dispatch:
| Before | After |
|---|---|
ForceDropPickup | _ForceDropPickup |
IsHeld | _IsHeld |
IsOccupied | _IsOccupied |
StopSound | _StopSound |
SlowUpdate | _SlowUpdate |
Update Inspector event strings, SendCustomEvent* calls, delayed events and nameof(...) expressions, and cross-behaviour calls. Compatibility aliases are not provided because an old unprefixed alias would restore the same legacy network exposure.
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) | A mirror adds another costly scene render; the impact depends on view, scene, resolution, and device | Default Mirror OFF; add a player-controlled toggle and profile each target device |
| 2 | Use realtime directional lights with real-time shadows without profiling | Realtime shadow cost varies with scene geometry, view, and target device and can dominate frame time on Android | Prefer baked lightmaps + light probes; profile the target device before keeping any realtime shadows |
| 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 an Android build profile | Post-processing is disabled at runtime on Android, so the authored effect will not appear and unnecessary resources can still enlarge the build | Use a separate Android build profile with post-processing removed |
| 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 Cloth on Android, or add many Unity Constraints without profiling | Cloth is disabled on Android. Unity Constraints are permitted in worlds, but overuse can significantly affect performance | Remove Cloth from the Android build; prefer VRC Constraints for new work and profile any constraint-heavy setup |
| 8 | Upload without completing a lightmap bake | Realtime GI adds substantial scene-dependent render cost and is unsuitable as an unmeasured fallback on Android | Bake lights before upload, then verify the result on the target device |
| 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 (PC) / 5-10 (Quest) 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 |
Configuring Dynamics for Worlds (PhysBones, Contacts, Box Contacts, Global Avatar PhysBone Colliders, world VRCPhysBoneCollider access) | components.md | layers.md, troubleshooting.md; use unity-vrc-udon-sharp for Udon code | audio-video.md, lighting.md | Dynamics component availability and Udon access are SDK-version sensitive |
| 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 / voice zones (SetVoiceGain, Steam Audio) | audio-video.md, components.md | troubleshooting.md | lighting.md, performance.md | AVPro vs Unity Video selection is VRChat-specific |
| Configuring WorldQualitySettings, realtime probes, or Shadowmask Mode | components.md | lighting.md; Udon API: unity-vrc-udon-sharp | audio-video.md, layers.md | Existing startup setters and override flags can overwrite authored quality choices |
| Baking lights / lightmap setup | lighting.md, performance.md | — | audio-video.md, layers.md | Lightmap resolution and probe placement affect Quest VRAM |
| SDK Build Panel validation alerts, red/yellow/white warnings, or Auto Fix questions | build-validation.md | upload.md, troubleshooting.md | audio-video.md, lighting.md | Alert severity, build consequence, and Auto Fix side effects must come from SDK-backed catalog |
| World upload and publish | upload.md | build-validation.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
More from niaka3dayo
Use this skill in a project
Open any RiverX project, search the Skills panel for niaka3dayo/agent-skills-vrc-udon/unity-vrc-world-sdk-3, and install it in one click.