1. A method, performed on one or more processors, for blending textures of a composite image formed by a plurality of source images mapped onto a three dimensional model, comprising: projecting the composite image to obtain a two dimensional, unblended, projected image having textures; blending the textures of the unblended projected image to obtain a blended projected image; backprojecting the unblended projected image and the blended projected image onto the three dimensional model; determining a difference between a pixel of the backprojected, blended image and a corresponding pixel of the backprojected, unblended image; and applying the determined difference to a further corresponding pixel of the composite image to obtain a modified composite image representing a blending of the plurality of source images in the composite image.