Figure 5. Displaying contour lines on the surface of a half cylinder in IRIS Explorer 3.5. The data values at the nodes of the cylindrical grid are read into the map as a lattice, and then converted to a pyramid using the LatToPyr module. ExteriorPyr is then used to obtain the outside of the pyramid (i.e. the set of unshared faces) and the new ContourPyr module calculates the contours on those faces.