1. A processor-implemented method for visual simultaneous localization and mapping, the method comprising: initializing a three-dimensional (3D) target based on a first set of target 3D points obtained from a first reference image, wherein the target 3D points in the first set are initialized along a plane at a predetermined initial depth value prior to processing a subsequent image; processing one or more subsequent images; tracking the 3D target in six degrees of freedom; and refining the 3D target based on subsequent sets of target 3D points obtained from the processing of the one or more subsequent images, each subsequent set of target 3D points corresponding to one of the one or more subsequent images.