What causes "Engine is disposed" in BabylonJS/Babylon.js?

End the XR session and dispose XR providers before engine.dispose().

Engine is disposed

Error message

Engine is disposed

What it means

_createRenderTargetTexture builds a Babylon RenderTargetTexture around the XR layer's framebuffer/color texture. The provider stores an engine reference; if the engine was disposed (reference cleared), creating new GPU resources is impossible and this error is thrown before any allocation.

Source

Thrown at packages/dev/core/src/XR/webXRWebGLRenderTargetTextureProvider.ts:38

        }
        const internalTexture = new InternalTexture(this._engine, InternalTextureSource.Unknown, true);
        internalTexture.width = textureSize.width;
        internalTexture.height = textureSize.height;
        internalTexture._hardwareTexture = new WebGLHardwareTexture(texture, gl);
        internalTexture.isReady = true;
        return internalTexture;
    }

    protected _createRenderTargetTexture(
        width: number,
        height: number,
        framebuffer: Nullable<WebGLFramebuffer>,
        colorTexture?: WebGLTexture,
        depthStencilTexture?: WebGLTexture,
        multiview?: boolean
    ): RenderTargetTexture {
        if (!this._engine) {
            throw new Error("Engine is disposed");
        }

        const textureSize = { width, height };

        const renderTargetTexture = this._createRenderTargetTextureShell(width, height, !!multiview);
        const renderTargetWrapper = renderTargetTexture.renderTarget as WebGLRenderTargetWrapper;
        // Set the framebuffer, make sure it works in all scenarios - emulator, no layers and layers.
        // This must happen before binding any texture, since setTexture binds it to the framebuffer.
        if (framebuffer || !colorTexture) {
            renderTargetWrapper._framebuffer = framebuffer;
        }

        // Create internal texture
        if (colorTexture) {
            if (multiview) {
                renderTargetWrapper._colorTextureArray = colorTexture;
            } else {
                const internalTexture = this._createInternalTexture(textureSize, colorTexture);

View on GitHub (pinned to 0592b347b8)

Solutions

End the XR session and dispose XR providers before engine.dispose().
Guard calls with a liveness check (`if (provider is alive)` / check engine not disposed) before fetching render target textures.
Recreate the XR session manager, layers and texture providers after building a new engine.
Defer/ignore render-target requests during teardown (e.g. null out frame callbacks first).

Example fix

// before
engine.dispose();
const rtt = provider.getRenderTargetTextureForEye(eye); // throws
// after
const rtt = provider.getRenderTargetTextureForEye(eye);
provider.dispose?.();
engine.dispose();

Defensive patterns

Strategy: try-catch

Validate before calling

if (!provider || provider._engine == null /* disposed */) {
  return null; // engine disposed; cannot create RTT
}

Type guard

function providerUsable(provider: WebXRWebGLRenderTargetTextureProvider): boolean {
  // @ts-expect-error internal
  return provider._engine != null;
}

Try / catch

try {
  const rtt = provider.getRenderTargetTextureForEye(eye);
} catch (e) {
  if (e instanceof Error && e.message === 'Engine is disposed') {
    console.warn('Skipping XR RTT fetch during engine teardown');
    return null;
  }
  throw e;
}

Prevention

End the XR session and dispose providers before engine.dispose()
Null out XR frame callbacks before teardown so late requests are avoided
Rebuild XR providers when recreating an engine after context loss
Guard render-target fetches with an engine-alive check

When it happens

Trigger: Requesting getRenderTargetTextureForEye(...) (or a layer RTT refresh) after engine.dispose(); an XR frame callback still running while the engine is being torn down; reusing a texture provider created with an old engine after engine recreation.

Common situations: Shutdown-order bug: engine.dispose() before ending the XR session; app teardown where XR compositor calls back into a disposed provider; swapping engines (context loss recovery) without rebuilding XR providers.

Related errors

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/be1ac3215185cb4e. Report an issue: GitHub.