BabylonJS/Babylon.js · error

Cannot get NaN of ${a}

Error message

Cannot get NaN of ${a}

What it means

The IsNaN flow graph block calls _polymorphicIsNan, which uses isNumeric(a, true) — a variant that accepts numbers and FlowGraphInteger values only (the second argument is not the boolean-tolerant mode here). If the input is a boolean, string, vector, or other FlowGraphTypes value, the block throws instead of returning a result. NaN checks only make sense for numeric inputs, so non-numeric input is treated as an authoring error.

Source

Thrown at packages/dev/core/src/FlowGraph/Blocks/Data/Math/flowGraphMathBlocks.pure.ts:858

    private _polymorphicGreaterThanOrEqual(a: FlowGraphNumber, b: FlowGraphNumber) {
        return ComparisonOperators(a, b, (a, b) => a >= b);
    }
}

/**
 * Is NaN block.
 */
export class FlowGraphIsNanBlock extends FlowGraphUnaryOperationBlock<FlowGraphNumber, boolean> {
    constructor(config?: IFlowGraphBlockConfiguration) {
        super(RichTypeAny, RichTypeBoolean, (a) => this._polymorphicIsNan(a), FlowGraphBlockNames.IsNaN, config);
    }

    private _polymorphicIsNan(a: FlowGraphNumber) {
        if (isNumeric(a, true)) {
            return isNaN(getNumericValue(a));
        } else {
            throw new Error(`Cannot get NaN of ${a}`);
        }
    }
}

/**
 * Is Inf block.
 */
export class FlowGraphIsInfinityBlock extends FlowGraphUnaryOperationBlock<FlowGraphNumber, boolean> {
    constructor(config?: IFlowGraphBlockConfiguration) {
        super(RichTypeAny, RichTypeBoolean, (a) => this._polymorphicIsInf(a), FlowGraphBlockNames.IsInfinity, config);
    }

    private _polymorphicIsInf(a: FlowGraphNumber) {
        if (isNumeric(a)) {
            return !isFinite(getNumericValue(a));
        } else {
            throw new Error(`Cannot get isInf of ${a}`);
        }

View on GitHub (pinned to 0592b347b8)

Solutions

1. Feed the IsNaN block a numeric input only; if the value may be missing, provide a numeric default (e.g. 0) upstream before the block.
2. Replace the IsNaN block with a type/value check block appropriate to the actual data type being tested.
3. Inspect the connection in the flow graph editor and remove the wrong-typed wire feeding the block.

Example fix

// before: boolean into IsNaN
isNaNBlock.value.connect(logicBlock.output); // throws

// after: numeric input
isNaNBlock.value.connect(divideBlock.output); // number input is valid

// before IsNaN block runs
function validIsNanInput(v) {
  return typeof v === 'number' || (typeof v === 'object' && v !== null && 'value' in v);
}
if (!validIsNanInput(isNanInput)) throw new TypeError('IsNaN input must be a number or FlowGraphInteger');

function isNumericValue(v): v is number | FlowGraphInteger {
  return typeof v === 'number' || (typeof v === 'object' && v !== null && 'value' in v);
}

try {
  result = isNanBlock.evaluate(context);
} catch (e) {
  if (e.message.startsWith('Cannot get NaN of')) {
    result = false; // or handle as 'input was not numeric'
  } else { throw e; }
}

When it happens

Trigger: Connecting a non-numeric connection (boolean, string, Vector2/3/4, Quaternion, FlowGraphInteger is OK) into the IsNaN block's input and executing the block.

Common situations: Using IsNaN to test whether an optional/undefined input 'is empty' — the wiring carries a wrong-typed default value; passing a boolean from a logic block into IsNaN; graph serialization assigning a string to the input.

Related errors

• Cannot compare ${a} and ${b}
• Cannot get isInf of ${a}
• Cannot perform bitwise AND on ${a} and ${b}
• Cannot perform bitwise OR on ${a} and ${b}
• Cannot perform bitwise XOR on ${a} and ${b}

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/7d0b88d5071442e9. Report an issue: GitHub.