<pc-wasm>

The <pc-wasm> tag loads a WebAssembly module the engine needs before the application starts — Ammo for physics, Basis or DracoDecoderModule for compressed assets.

Usage

• It must be a direct child of <pc-app>.

Attributes

Attribute	Type	Default	Description
fallback	String	-	Path to fallback (asm.js) code when WebAssembly is not supported. The Draco decoder ignores it
glue	String	-	Path to the JavaScript glue code for the module
name	String	-	Module name used to reference it in scripts
wasm	String	-	Path to the WebAssembly (.wasm) file

The name is case-sensitive — the engine looks the module up by exact name. The modules consumed by the engine are Ammo (physics), Basis (texture transcoding) and DracoDecoderModule (mesh decompression).

When these are read

The attributes are read once, when the module starts loading — on the element's first connection to the document, or earlier if a containing <pc-app> boots first and collects it. Changing them afterwards has no effect. Creating the element programmatically works as you would expect: set the attributes before appending the element to the document.

Readiness

The element initializes asynchronously and becomes ready once its module has loaded: it fires the standard ready event and can be awaited with whenReady('pc-wasm') — see Programmatic Access. (Basis is the exception: it is ready as soon as its transcoder starts loading.) You will rarely need to, though: a <pc-app> waits for every <pc-wasm> among its children before creating its graphics device, so an app that is ready is an app whose modules have loaded. A <pc-wasm> nested any deeper still loads, but the app does not wait for it.

Readiness is deliberately sticky. A WebAssembly module configures engine-global state that never unloads, so removing the element does not return it to a pending state, and re-inserting it does not load the module again.

A <pc-wasm> without a name logs a warning and never becomes ready — but it does not block the containing <pc-app> from booting. A module that fails to load, from a mistyped URL or a server that refuses it, is worse: the element never becomes ready and its <pc-app> never starts, with only a failed to initialize module=... error in the console to show for it.

Declare Ammo in the markup rather than adding it later. The engine looks for the physics module once, as the application starts, so an app that booted without it runs without physics.

Example

Loading the Ammo physics module. The box only falls because the module is declared — the app waits for it before booting, so physics is ready when the scene starts. Try removing the <pc-wasm> tag and re-running:

Live Example

<pc-app>
    <!-- Load the ammo.js WebAssembly module -->
    <pc-wasm name="Ammo" glue="https://developer.playcanvas.com/assets/modules/ammo/ammo.wasm.js" wasm="https://developer.playcanvas.com/assets/modules/ammo/ammo.wasm.wasm" fallback="https://developer.playcanvas.com/assets/modules/ammo/ammo.js"></pc-wasm>
    <pc-scene>
        <pc-entity name="camera" position="0 2 6">
            <pc-camera clear-color="#1d1f2b"></pc-camera>
        </pc-entity>
        <pc-entity name="light" rotation="45 30 0">
            <pc-light cast-shadows normal-offset-bias="0.05" shadow-bias="0.2"></pc-light>
        </pc-entity>
        <pc-entity name="crate" position="0 4 0" rotation="25 15 35">
            <pc-render type="box"></pc-render>
            <pc-collision></pc-collision>
            <pc-rigid-body type="dynamic"></pc-rigid-body>
        </pc-entity>
        <pc-entity name="ground" position="0 -0.5 0" scale="10 1 10">
            <pc-render type="box"></pc-render>
            <pc-collision half-extents="5 0.5 5"></pc-collision>
            <pc-rigid-body type="static"></pc-rigid-body>
        </pc-entity>
    </pc-scene>
</pc-app>

JavaScript Interface

You can programmatically create and manipulate <pc-wasm> elements using the WasmElement API.

The element exposes no engine object of its own. Once it is ready the module has been instantiated through the engine's WasmModule under its name (Basis goes through the engine's Basis initializer instead). Ammo's glue script defines the global Ammo, so scripts can use it directly; reach other modules through WasmModule.getInstance(name, callback).

See Also

• <pc-rigid-body> — physics, the usual reason to load Ammo
• <pc-collision> — collision shapes for physics
• <pc-app> — waits for every module before it boots

Examples: Basic Physics, Vehicle Physics and Video Texture.