Thanks Laurie and Varian, the problem is solved! On a different note, how can I incorporate bump maps with these models to give a relative representation of topographic heights, the bump tab is just for functions? As you are aware, there are certain planetary features, like Olympus Mons on Mars, that are not "flat" on the sphere, standing as it does 20km high! So if one has a proper grey-scale image for the whole height range of the planet how can this be combined with the 2-D colour map to create the illusion of topography? Mixing materials is not a solution. Thanks. Lester