A Uniform Sky Illumination Model to Enhance Shading of Terrain and Urban Areas

  title={A Uniform Sky Illumination Model to Enhance Shading of Terrain and Urban Areas},
  author={Peter J. Kennelly and A. James Stewart},
  journal={Cartography and Geographic Information Science},
  pages={21 - 36}
Users of geographic information systems (GIS) usually render terrain using a point light source defined by an illumination vector. A terrain shaded from a single point provides good perceptual cues to surface orientation. This type of hill shading, however, does not include any visual cues to the relative height of surface elements. We propose shading the terrain under uniform diffuse illumination, where light arrives equally from all directions of a theoretical sky surrounding the terrain… 
Maps shading terrain as if illuminated by a point light source (i.e. hill-shading) are commonly used in cartographic displays. These hill-shaded maps are especially important for representing
This contribution explores alternative terrain visualization techniques based on diffuse, rather than direct, illumination and shows that such a visualization improves the recognition of local scale features on high resolution DEMs, which is very important in different applications: visual inspection of DEM, recognition of archaeological features, etc.
General sky models for illuminating terrains
It is argued that this process of creating hill-shaded visualizations of terrain with sky models shows parallels to other geo-simulations, and that basing such work on standards from the computer graphics industry shows potential for its use in VGE.
While conventional relief shading based on hillslope and illumination models has a long and successful history for visualization of mountainous topography, it also suffers certain limitations. Among
Comparison of Relief Shading Techniques Applied to Landforms
The aim of this work is to evaluate analytical hillshading methods against a set of landforms within an online survey and revealed that the clear sky model performs best applied to most of the landforms included in the survey, in particular all the mountain and valley types.
Terrain maps displaying hill-shading with curvature
A methodology for producing realistic hill-shading map based on shaded relief map, digital orthophotographic map fusion and IHS transformation
This research indicates that when the method of fusing the processed SRM with the IHS color system is used, the optimum index factor (OIF) and entropy of the generated map are much greater than for the results of the traditional method, which can greatly enhance the terrain effect.
A novel method for determining sky view factor for isotropic diffuse radiations for a collector in obstacles-free or urban sites
A novel method for computing sky view factor for isotropic diffuse radiations on tilted collectors located in obstacle free and urban sites has been introduced in this paper. The proposed method
Improving the representation of major landforms in analytical relief shading
An automated digital method is introduced that produces shaded relief with locally adjusted illumination directions to simulate the techniques and cartographic principles of manual relief shading and best highlights major landforms in terrain characterized by sharp, clearly defined ridges and valleys.
Automated Reduction of Visual Complexity in Small-Scale Relief Shading
A new method of generalizing digital elevation models for deriving small-scale shaded relief that resembles the manual style is proposed, which consists of the following raster operations.


Fast Horizon Computation at All Points of a Terrain With Visibility and Shading Applications
  • A. J. Stewart
  • Computer Science
    IEEE Trans. Vis. Comput. Graph.
  • 1998
Experimental and theoretical results are presented which show that the algorithm is more accurate that previous algorithms and is faster than previous algorithms in terrains of more than 100,000 sample points.
Vicinity shading for enhanced perception of volumetric data
A shading model for volumetric data which enhances the perception of surfaces within the volume by incorporating uniform diffuse illumination, which arrives equally from all directions at each surface point in the volume.
A Loosely Synchronous, Parallel Algorithm for Hill Shading Digital Elevation Models
Results for several digital elevation models indicate that when compared with a serial implementation, the parallel algorithm reduces solution limes by over 70% when four processors are used.
Vectorial algebra algorithms for calculating terrain parameters from DEMs and solar radiation modelling in mountainous terrain
  • J. Corripio
  • Environmental Science
    Int. J. Geogr. Inf. Sci.
  • 2003
Terrain parameters derived from digital elevation models (DEMs), such as slope gradient, aspect and cell surface area, are represented as a vector normal to the surface and calculated using the
Visualizing topography by openness: A new application of image processing to digital elevation models
A new parameter, here termed openness, expressing the degree of dominance or enclosure of a location on an irregular surface, is developed to visualize topographic character. Openness is an angular
Towards accurate recovery of shape from shading under diffuse lighting
  • A. J. Stewart, M. Langer
  • Computer Science
    Proceedings CVPR IEEE Computer Society Conference on Computer Vision and Pattern Recognition
  • 1996
We present a surface radiance model for diffuse lighting that incorporates shadows, interreflections, and surface orientation. We show that, for smooth surfaces, the model is an excellent
The rendering of relief images from digital contour data
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, and offers a number of benefits for additional processing because of computational economy and efficiency.
A Model for Automatic Hill-Shading
A model which combines three of the parameters of the "Swiss manner" of relief representation with the Yoeli method of analytical hill-shading is presented, which allows a general change in tonal value as a function of altitude.
An investigation of RGB multi-band shading for relief visualisation
Relief shading using digital elevation models