API Reference > geometry-core > Serialization > BGFBAccessors > BGFBAccessors.InterpolationCurve > startTangent startTangent Method startTangent(obj?: BGFBAccessors.DPoint3d): | BGFBAccessors.DPoint3d Parameter Type Description obj BGFBAccessors.DPoint3d Returns - | BGFBAccessors.DPoint3d DPoint3d|null Defined in serialization/BGFBAccessors.ts Line 1983 Last Updated: 12 June, 2024