1. A method of rendering image data for effecting the production of sub-images by a multi-view display, the method comprising the steps of: receiving a first image signal representing a first image comprising 3D image data not yet rendered for multi-view display; spatially filtering the first image signal to provide a second image signal, the second image signal representing a second image, the spatial filtering comprising mapping an image element of the first image to at least one image element of the second image, where a strength of the spatial filter is dependent on a depth of the image element of the first image relative to a reference depth of the first image; sampling the second image signal to define a plurality of said sub-images, each sub-image being associated with a different respective view direction of the image; and displaying said plurality of said sub-images on the multi-view display, wherein a visibility factor is applied to the at least one image element of the second image, the visibility factor being determined from a distance between a viewpoint and a spatial coordinate of the image element of the first image and a distance between the viewpoint and a spatial coordinate of the at least one image element of the second image, and wherein the visibility factor is equal to zero when the at least one image element of the second image is closer than the image element of the first image to the viewpoint, and where the visibility factor is equal to one when the image element of the first image is closer than the at least one image element of the second image to the viewpoint, and where the visibility factor follows a gradual transition between the values of zero and one.