1. A system comprising: one or more processors; a camera configured to capture an image of a scene that includes a hand, the image having pixels corresponding to points of the scene; one or more computer-readable media storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform acts comprising: analyzing the image to identify contour points of the hand; determining a plurality of feature sets for the contour points, wherein the plurality of feature sets includes a first feature set corresponding to a first contour point and a second contour point, the first feature set includes a distance value corresponding to a distance between the first contour point and the second contour point, and the first feature set includes an angle value corresponding to an angle between a tangent of the first contour point and a line connecting the first and second contour points; generating a higher level histogram having multiple higher level bins, wherein each higher level bin corresponds to a distance interval and an angle interval, and wherein a bin value of each higher level bin is equal to a first number of feature sets of the plurality of feature sets having (a) a distance value corresponding to a distance within the distance interval of the higher level bin and (b) an angle value corresponding to an angle within the angle interval of the higher level bin, and wherein a size of a distance interval of a first higher level bin is different from a size of a distance interval of a second higher level bin, and a size of an angle interval of the first higher level bin is different from a size of an angle interval of the second higher level bin; comparing each bin value of the higher level histogram with a corresponding bin value of a reference histogram, wherein the reference histogram corresponds to a reference hand pose; analyzing feature sets of at least one higher level bin of the multiple higher level bins of the higher level histogram; generating, based at least in part on the analyzing, a lower level histogram having multiple lower level bins, wherein each lower level bin corresponds to a distance interval smaller than a distance interval of the at least one higher level bin and an angle interval smaller than an angle interval of the at least one higher level bin, and wherein a bin value of each lower level bin is equal to a second number of feature sets having (a) a distance value corresponding to a distance within the distance interval of the lower level bin and (b) an angle value corresponding to an angle within the angle interval of the lower level bin; and determining a hand gesture of the hand based at least in part on the reference histogram.