BabylonJS/Babylon.js · error

Failed to get 2D context

Error message

Failed to get 2D context

What it means

To read raw RGBA pixels for SOG splat data, LoadWebpImageData obtains a 2D rendering context from the created canvas via getContext("2d"). If the context is unavailable (null), pixel data cannot be extracted and this error is thrown. Some environments create canvases without 2D context support (e.g. WebGL-only canvases).

Source

Thrown at packages/dev/loaders/src/SPLAT/sog.pure.ts:114

}
const SH_C0 = 0.28209479177387814;

async function LoadWebpImageData(rootUrlOrData: string | Uint8Array, filename: string, engine: AbstractEngine): Promise<IWebPImage> {
    const promise = new Promise<IWebPImage>((resolve, reject) => {
        const image = engine.createCanvasImage();
        if (!image) {
            throw new Error("Failed to create ImageBitmap");
        }
        image.onload = () => {
            try {
                // Draw to canvas
                const canvas = engine.createCanvas(image.width, image.height);
                if (!canvas) {
                    throw new Error("Failed to create canvas");
                }
                const ctx = canvas.getContext("2d");
                if (!ctx) {
                    throw new Error("Failed to get 2D context");
                }
                ctx.drawImage(image, 0, 0);

                // Extract pixel data (RGBA per pixel)
                const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
                resolve({ bits: new Uint8Array(imageData.data.buffer), width: imageData.width, height: imageData.height });
            } catch (error) {
                // eslint-disable-next-line @typescript-eslint/prefer-promise-reject-errors
                reject(`Error loading image ${image.src} with exception: ${error}`);
            }
        };
        image.onerror = (error) => {
            // eslint-disable-next-line @typescript-eslint/prefer-promise-reject-errors
            reject(`Error loading image ${image.src} with exception: ${error}`);
        };

        image.crossOrigin = "anonymous"; // To avoid CORS issues
        let objectUrl: string | undefined;

View on GitHub (pinned to 0592b347b8)

Solutions

1. Use a canvas implementation that supports 2D contexts (browser canvas, node-canvas, or full OffscreenCanvas support).
2. Do not pass a canvas already used for WebGL as the 2D extraction target; create a dedicated canvas.
3. Update the polyfill/engine so createCanvas returns a fresh 2D-capable canvas.
4. Catch the rejection and fall back to an alternative WebP decoder (e.g. decodeImage + manual RGBA conversion).

Example fix

// before
const sharedCanvas = engine.getRenderingCanvas();
sharedCanvas.getContext("webgl"); // earlier
// later getContext("2d") -> null -> error
// after
const extractCanvas = document.createElement("canvas"); // dedicated 2D canvas
const ctx = extractCanvas.getContext("2d");

const probe = document.createElement("canvas").getContext("2d");
if (!probe) {
  throw new Error("2D canvas context unavailable; cannot extract SOG pixels");
}

function has2DContext(engine: AbstractEngine): boolean {
  const c = (engine as any).createCanvas?.(1, 1);
  return !!c && !!c.getContext("2d");
}

try {
  const data = await loadMeansImageAsync(url, engine);
} catch (e) {
  if (String(e.message) === "Failed to get 2D context") {
    // fallback: decode with OffscreenCanvas(2d) or a WASM WebP decoder
    const off = new OffscreenCanvas(w, h);
    const ctx = off.getContext("2d");
  } else throw e;
}

When it happens

Trigger: canvas.getContext("2d") returning null during image.onload — canvas backend without 2D support, or a canvas previously acquired with a different context type.

Common situations: Polyfilled canvas whose getContext only supports 'webgl'; engines reusing a canvas already bound to a WebGL context; restricted environments (WebGL-only headless renderers).

Related errors

• Failed to create ImageBitmap
• Failed to create canvas
• filename is required when using a URL
• Missing arrays in SOG data.
• WebGL not supported

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/a98ec430ae0b64c8. Report an issue: GitHub.