1. A system for open doorway detection for autonomous robot exploration, the system comprising: an onboard range sensor, the range sensor operable for constructing a three-dimensional (3D) point cloud of a scene; one or more processors and a memory, the memory being a non-transitory computer-readable medium having executable instructions encoded thereon, such that upon execution of the instructions, the one or more processors perform operations of: receiving a 3D point cloud from the range sensor, the 3D point cloud having a plurality of cloud points; filtering and downsampling the 3D point cloud to remove cloud points outside of a predefined range and reduce a size of the point cloud and, in doing so, generating a filtered and downsampled 3D point cloud; extracting vertical planes from the filtered and downsampled 3D point cloud; and identifying open doorways from each extracted vertical plane.