Abstract: A non-transitory computer readable medium that stores instructions that once executed by a computer cause the computer to execute the stages of: calculating a first function that represents an object that is three dimensional; calculating a second function that is a convolution or an approximated convolution of (a) the first function applied on points of the object, and (b) an other function that is the first function composed with a function that sends points of the object to opposite points; wherein the second function is translation invariant; and calculating the translation and rotation invariant features of the query object, based on the second function.