AbstractExisting methods of modelling and rendering relief from digitised contours adopt either regular grid or triangulated irregular network approaches. Both can have disadvantages which include imprecise terrain modelling, ineffective visualisation, and/or heavy computing overheads.An alternative approach has been developed which calculates profiles across the contour model, typically at about 1 mm separation at the visualisation scale, in the direction of an assumed illumination source. Intensity values are calculated for the profile swathes by considering profile gradient and local slope characteristics. The resulting shaded model gives an effective visualisation, and offers a number of benefits for additional processing because of computational economy and efficiency.Single light source images of shaded relief are often incomplete in their rendering because they favour relief trend lines in certain directions only. A technique has been developed to overlay generated shaded images from a range of ill...
[1]
Victor J. D. Tsai,et al.
Delaunay Triangulations in TIN Creation: An Overview and a Linear-Time Algorithm
,
1993,
Int. J. Geogr. Inf. Sci..
[2]
Henry W. Castner,et al.
Re-assessing the Role Played by Shaded Relief in Topographic Scale Maps
,
1979
.
[3]
Berthold K. P. Horn,et al.
Hill shading and the reflectance map
,
1981,
Proceedings of the IEEE.
[4]
Richard J. Phillips.
An Experiment with Contour Lines
,
1979
.
[5]
Kurt Brassel.
A Model for Automatic Hill-Shading
,
1974
.
[6]
Bui Tuong Phong.
Illumination for computer generated pictures
,
1975,
Commun. ACM.