BabylonJS/Babylon.js · error · Error

Constant value must be between 0.0 and 1.0

Error message

Constant value must be between 0.0 and 1.0

What it means

In MergeTexturesAsync, a constant channel input fills an output channel with a fixed scalar that is written into an 8-bit texture, so it must be between 0.0 and 1.0. This error is thrown when channel.value falls outside that range.

Source

Thrown at packages/dev/core/src/Materials/Textures/textureMerger.ts:124

        const channel = channels[channelIndex];
        if (channel) {
            if (IsTextureInput(channel)) {
                // Validate source channel
                if (channel.sourceChannel < 0 || channel.sourceChannel > 3) {
                    throw new Error("Source channel must be between 0 and 3 (R, G, B, A)");
                }

                // Find or add texture to inputs
                let textureIndex = textureInputs.indexOf(channel.texture);
                if (textureIndex === -1) {
                    textureIndex = textureInputs.length;
                    textureInputs.push(channel.texture);
                }
                textureInputMap[channelIndex] = textureIndex;
            } else if (IsConstantInput(channel)) {
                // Validate constant value
                if (channel.value < 0 || channel.value > 1) {
                    throw new Error("Constant value must be between 0.0 and 1.0");
                }
                textureInputMap[channelIndex] = -1;
            } else {
                throw new Error("Invalid channel input configuration");
            }
        } else {
            textureInputMap[channelIndex] = -1;
        }
    }

    // Determine output size
    let outputSize = config.outputSize;
    if (!outputSize && textureInputs.length > 0) {
        // Use the largest texture size
        let maxSize = 0;
        for (const texture of textureInputs) {
            const size = texture.getSize();
            const currentSize = Math.max(size.width, size.height);

View on GitHub (pinned to 0592b347b8)

Solutions

1. Convert byte-scale constants: divide by 255 (e.g. 255 -> 1.0).
2. Clamp the value: Math.min(1, Math.max(0, value)) before passing it.
3. Check upstream computations (factors, sliders) for units that are not normalized.

Example fix

// before
{ value: 255 }
// after
{ value: 1.0 } // or 255 / 255

function clamp01(v: number): number {
  return Math.min(1, Math.max(0, v));
}
const safeInput = { value: clamp01(rawFactor) };

function isUnitValue(v: unknown): v is number {
  return typeof v === "number" && Number.isFinite(v) && v >= 0 && v <= 1;
}

try {
  const tex = await MergeTexturesAsync(channels, w, h, scene);
} catch (e) {
  if (String(e.message).includes("Constant value must be between 0.0 and 1.0")) {
    console.error("Constant is out of 0-1 range; check 0-255 scale confusion.");
  }
}

When it happens

Trigger: Passing a constant input like { value: 255 } (authoring in 0-255) or a negative value to MergeTexturesAsync / CreateMergedAnisotropyTexture / metalRough conversion.

Common situations: Porting code that used byte values (0-255), computing a factor with NaN or a bad division producing out-of-range numbers, glTF material factor units confusion.

Related errors

• Source channel must be between 0 and 3 (R, G, B, A)
• Sample2DRgbaToRef: widthPx and heightPx must be positive.
• At least one mesh is needed to create the nav mesh.
• At least one mesh is needed to create the nav mesh.
• Unable to create navmesh. No navMesh or navMeshQuery returne

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/f7193b8c86190cc9. Report an issue: GitHub.