1. A method of providing data defining an image of a scene, the method comprising the steps of: (a) providing a plurality of starting pixel data elements, each said starting pixel data element incorporating data corresponding to illumination seen along a starting pixel ray vector associated with that starting pixel data element, each said starting pixel ray vector having a direction and an intercept on a locus; and (b) forming said pixel data elements into a transform image including a plurality of direction matrices, each said direction matrix including pixel data elements associated with pixel ray vectors having directions parallel within a preselected direction tolerance range to a common ray direction.