1. A method of identifying large planar surfaces in scenes, comprising: at a computing device having one or more processors, and memory storing one or more programs configured for execution by the one or more processors: receiving a plurality of captured IR images of a scene taken by a 2-dimensional array of image sensors of a camera that has a plurality of IR illuminators proximate to the array of image sensors, wherein each IR image is captured when a distinct subset of the IR illuminators of the camera is illuminated; constructing a depth map of a scene using the plurality of IR images; using the depth map to compute a binary depth edge map for the scene, wherein the binary depth edge map specifies lines of depth discontinuities in the depth map; identifying a plurality of image regions enclosed by lines of depth discontinuities in the binary depth edge map; determining that a first image region of the plurality of image regions represents a large planar surface in the scene by: fitting a plane to points in the first component; determining the orientation of the plane; and determining that the plane fitting residual error is less than a predefined threshold; and identifying a region in a displayed RGB image of the scene taken by the camera, wherein the region in the RGB image corresponds to the first image region.