Manya,N., Benger,W., Ritter,M., Ayyala,I.A., Justic,D., Wang,L.
Abstract:
Hypsometric tints and contour lines are standard techniques for depicting height information used in geosciences. In this paper, we present a rendering algorithm for bathymetric and topographic data based on these well-known and intuitive methods. In addition to linear mapping of height values to colors, we also explore a non-linear mapping that is able to depict the fine details over a large value range superior to the usual linear mapping. In particular, when considering coastal data, this non-linear mapping emphasizing small deviations above and below the ocean surface becomes very effective, as will be demonstrated upon a data set covering the flat marsh lands of the Barataria bay in southern Louisiana. Contour lines complement the color-coding by providing means to read off height values quantitatively over a large range. These lines are computed in the shader directly as a part of the surface rendering process instead of computing them explicitly as lines.Special attention is given to avoid visual clutter and allow multiple types of contour lines describing different height levels. The edges of the lines are smoothened to avoid moire effects and seamless blending when inspecting the data sets from a distance. This algorithm is demonstrated on three different applications data sets(the Gulf coast data set covering the Barataria bay, a terrain data set describing a river bed and an analytic test data set implementing an icosahedron) to show forth the advantages of the nonlinear height mapping and the contour lines. While inspired by cartography, the methodology used here may well be used for quantitatively and qualitatively depiction of an arbitrary scalar feild on a surface.