1. A method for calculating a response value at a first voxel indicative of a global shape in an image, comprising the steps of: a. determining a value for each of at least one local shape descriptor at the first voxel; b. determining a spread function associated with the each of the at least one local shape descriptor; c. determining second voxels around the first voxel; d. calculating, in a processor, values for each the at least one local shape descriptor at each of the second voxels; e. determining a contribution of each of the second voxels at the first voxel based on the spread functions; and f. using a combination function to combine the contributions to determine the response value indicative of the global shape.