I’ve been seeing on the net more and more of beautiful maps made in 3D software, Blender mostly. The reason for venturing into 3D: shadows mostly. While we do have hillshading algorithms in most GIS packages, nothing can beat true ambient light for terrain visualisation. Shadows do not only give a natural feel to an image, they also provide important information on object shapes and depths (see examples below).

schema.png The basic idea od natural shading: modelling light paths.

How come we don’t have proper shading algorithms for cartographic purposes? Don’t know, but upon seeing all those ten-page tutorials for 3D software, I figured it wouldn’t be more difficult to simply build the algorithm for QGIS. (Well, it turned out to be more difficult than I imagined, as usual with coding …) Anyway, the algorithm is up and running in QGIS (landscapearchaeology.org/2019/qgis-shadows/). But that’s more of a proof of concept: I’ve started a Kickstarter campaign to develop a more robust algorithm and to integrate it in QGIS architecture (Processing toolbox). Support it and QGIS will be happy :).

What is the difference between “hillshading” and “natural shading”? (Neither of the terms is ideal…) Hillshade algorithms, as implemented in most GIS, model light reflectance, that is, the way light rays should bounce off a smooth surface. Natural shading, on the other hand, models unreflected light path, namely shadows which are produced in areas inaccessible to light from a particular light source. Therefore, true shading can be produced by combining the two: hillshade + natural shadows.

Shaded terrain examples

Coast of Dalmatia, Croatia.

Gergovia stronghold (France): Caesar’s army was defeated there (or at least retreated without seizing the Gaulish fortress…). Data: Lidar scan, www.craig.fr. Map: Elise Fovet, MSH Clermont-Ferrand.

Gergovia : detail of suface structures (modern period drystone walls and cairns, which may sometimes cover archaeological remains). Data: Lidar scan, www.craig.fr. Map: Elise Fovet, MSH Clermont-Ferrand.