Quickstart

TL;DR: Install the CCK Wasm package, add a CCKWasmProjectDescriptor to your content root, create a WasmBehaviour, log “Hello, world!”, build, and upload. If you’ve written a Unity script before, this takes under five minutes.

What you need

• Unity version matching the CVR CCK.
• The CVR.CCK.Wasm package imported into your project.
• An internet connection on the first build — the pipeline downloads .NET SDK 10 preview + WASI SDK + the CCK WasmModule into %LOCALAPPDATA%/ChilloutVR/CVRBuildTools/.

Status

C# WASM scripting is currently in closed (invite-only) testing. If you’re reading this from a published book, you’re either on the testing branch or documenting internally. The long-term plan is to replace CVR’s existing Lua scripting with this system.

Step 1 — Create the script

Unity menu: Assets > Create > CVR Wasm Behavior (C#).

Name the file HelloWorld.cs. You get:

using UnityEngine;
using WasmScripting;

public partial class HelloWorld : WasmBehaviour
{
    void Start()  { }
    void Update() { }
}

Three things to notice:

• using WasmScripting; — the namespace containing WasmBehaviour and the serialization attributes.
• : WasmBehaviour — every WASM-authorable script inherits from this, not MonoBehaviour directly.
• partial — required. The serialization generator emits a companion partial at build time.

Step 2 — Say hello

Replace the body of Start():

using UnityEngine;
using WasmScripting;

public partial class HelloWorld : WasmBehaviour
{
    void Start()
    {
        Debug.Log("Hello, world!");
    }

    void Update() { }
}

Debug.Log(string) is bound to CVR’s logging system. Strings go to the Unity console during Play Mode and to the CVR log in-game.

Step 3 — Attach to a GameObject

• Drop a primitive in the scene — GameObject > 3D Object > Cube.
• Select it.
• In the inspector, click Add Component, search for HelloWorld, and add it.

Step 4 — Wire a content descriptor

Your root content GameObject (the avatar, prop, or world root) needs a CCKWasmProjectDescriptor.

• Select the content root.
• Add Component > ChilloutVR Editor > CCK Wasm Project Descriptor.
• Leave everything default. The build processor will find your WasmBehaviour components automatically.

If your HelloWorld GameObject isn’t already a child of the content root, make it one.

Step 5 — Build

• Use the normal CCK flow (for a prop, select the CVRSpawnable and click Upload; for an avatar or world, the equivalent upload button).
• On the first build, watch the Unity console for Installing .NET SDK and Installing WASI SDK progress bars. It takes a few minutes once.
• On subsequent builds the pipeline is cached and completes in a few seconds.

Output lands at Assets/WasmModule.wasm, and WasmVMAnchor is added to the content root pointing at it.

Step 6 — See the log

When you join an instance with the built content, CVR loads the WASM module and dispatches Start. You should see:

Hello, world!

in the client log (or the Unity console if you tested in Play Mode).

That’s it — you have a running WASM script.

What to read next

• Authoring — full workflow, serialization attributes, descriptor fields.
• Events — what else you can hook (Update, OnPlayerJoined, triggers, etc.).
• Permissions — why certain calls throw and how to structure code around the sandbox.
• Examples — progressive examples up to a full racing system.
• Performance — keep your script fast as it grows.

If something went wrong

See Troubleshooting for the common errors — the first-build download hang, error CS0103 on a type that looks imported, WasmAccessDeniedException, or a script that compiles but silently does nothing.