1. A method, comprising: accessing a depth map that includes a plurality of depth pixels, the depth map is associated with an image coordinate system having a plane; estimating a local orientation for each depth pixel in a subset of the depth pixels, the local orientation is one or both of an in-plane orientation and an out-out-plane orientation relative to the plane of the image coordinate system; defining a local coordinate system for each of the depth pixels in the subset, each local coordinate system is based on the local orientation of the corresponding depth pixel; defining a feature region relative to the local coordinate system for each of the depth pixels in the subset; transforming the feature region for each of the depth pixels in the subset from the local coordinate system to the image coordinate system; and using the transformed feature regions to process the depth map.