API Reference > geometry-core > CartesianGeometry > Plane3dByOriginAndUnitNormal > velocity velocity Method Return the dot product of spaceVector with the plane's unit normal. This tells the rate of change of altitude for a point moving at speed one along the spaceVector. velocity(spaceVector: Vector3d): number Parameter Type Description spaceVector Vector3d Returns - number Defined in core/geometry/src/geometry3d/Plane3dByOriginAndUnitNormal.ts Line 217 Last Updated: 13 June, 2024