BabylonJS/Babylon.js · error · Error

Switch should have a single configuration object, the cases

Error message

Switch should have a single configuration object, the cases array

What it means

The flow/switch extraProcessor expects the glTF switch block to declare output flows (the case branches). It throws this error when the declaration op is not flow/switch or when gltfBlock.flows is missing/empty, because it needs to rename each non-default output flow to out_<case> on the serialized block.

Source

Thrown at packages/dev/loaders/src/glTF/2.0/Extensions/KHR_interactivity/declarationMapper.ts:1120

                const onlyIntegers = cases.value.every((caseValue) => {
                    // case value should be an integer. Since Number.isInteger(1.0) is true, we need to check if toString has only digits.
                    return typeof caseValue === "number" && /^-?\d+$/.test(caseValue.toString());
                });
                if (!onlyIntegers) {
                    Logger.Warn("Switch cases should be integers. Using empty array instead.");
                    cases.value = [] as number[];
                    return { valid: true };
                }
                // check for duplicates
                const uniqueCases = new Set(cases.value);
                cases.value = Array.from(uniqueCases) as number[];
            }
            return { valid: true };
        },
        extraProcessor(gltfBlock, declaration, _mapping, _arrays, serializedObjects) {
            // convert all names of output flow to out_$1 apart from "default"
            if (declaration.op !== "flow/switch" || !gltfBlock.flows || Object.keys(gltfBlock.flows).length === 0) {
                throw new Error("Switch should have a single configuration object, the cases array");
            }
            const serializedObject = serializedObjects[0];
            serializedObject.signalOutputs.forEach((output) => {
                if (output.name !== "default") {
                    output.name = "out_" + output.name;
                }
            });
            return serializedObjects;
        },
    },
    "flow/while": {
        blocks: [FlowGraphBlockNames.WhileLoop],
        outputs: {
            flows: {
                loopBody: { name: "executionFlow" },
            },
        },
    },

View on GitHub (pinned to 0592b347b8)

Solutions

1. Ensure the flow/switch block defines at least one entry in its "flows" object (plus optional "default")
2. Re-export the asset with a compliant KHR_interactivity exporter
3. Fix custom declaration mapping so this processor only handles flow/switch

Example fix

// before
{ "op": "flow/switch", "configuration": { "cases": { "value": [0,1] } } } // no flows
// after
{ "op": "flow/switch", "flows": { "0": {}, "1": {} }, "configuration": { "cases": { "value": [0,1] } } }

function validateSwitchBlock(block) {
  return typeof block.flows === "object" && block.flows !== null && Object.keys(block.flows).length > 0;
}
// verify each flow/switch block declares at least one flow before loading

const hasFlows = (b: { flows?: Record<string, unknown> | null }): b is { flows: Record<string, unknown> } => !!b.flows && Object.keys(b.flows).length > 0;

try {
  await loader.loadAsync(url);
} catch (e) {
  if (e instanceof Error && e.message.includes("Switch should have a single configuration")) {
    console.error("flow/switch block is missing its flows (cases) object.");
  } else throw e;
}

When it happens

Trigger: Loading an interactivity graph with a switch block that has no "flows" object, an empty flows map, or a block mis-mapped so this processor runs against a non-switch declaration.

Common situations: Exporter emitting switch with zero cases; hand-pruned JSON removing flows; custom declaration maps wiring the wrong op to the switch processor.

Related errors

• Receive event should have a single configuration object, the
• MultiGate should have a single configuration object, the num
• Event id should be a number
• Rotation quaternion input not found
• Variable index is not defined for variable interpolation blo

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/aac5f79056eb4c10. Report an issue: GitHub.