A method of rejecting the presence of an object of extrusion within a point cloud. The method comprising receiving, through a data interface, data describing a set of measurements of observed portions of the one or more objects in the scene. The method further comprising receiving data describing an extruded object that is hypothesized to exist in the scene. The method further comprising finding a set of near measurement points comprising measurement points wherein each measurement point is within a predefined distance of the hypothesized extruded object. The method further comprising classifying points within the set of near measurement points associated with the hypothesized extruded object as on-surface or off-surface. The method further comprising rejecting the hypothesized extruded object whose off-surface measurement points exceed an allowable threshold.