API Reference > geometry-core > Serialization > IModelJson > IModelJson.PlanarRegionProps > unionRegion unionRegion unionRegion: undefined | [IModelJson.PlanarRegionProps] {unionRegion:...} A collection of loops and parityRegions Defined in core/geometry/src/serialization/IModelJsonSchema.ts Line 144 Last Updated: 13 June, 2024