A method of coding, in the form of a digital file of a three-dimensional synthesis image, a model of an object formed by a stream of image elements (FEI) in which elementary images which are subsets of image elements {EIe}e=1e=ex are discriminated (A) in the stream (FEI), each elementary image is coded (B) according to an index value (n) representative of the elementary image, the numerical values (Zk,g,i) of the 3D synthesis image are calculated (C) and these values are stored in the form of a digital file. Application to 3D display involving an interactive dialogue with a user of a graphics application.