[Qgis-user] hillshade render style

[Andreas Plesch]

I could not find documentation on the hillshade render type style. While it
is rather self-explanatory, the multidirectional option could benefit from
explanation. I am looking at the source here:

http://qgis.org/api/2.18/qgshillshaderenderer_8cpp_source.html

and it points to

http://pubs.usgs.gov/of/1992/of92-422/of92-422.pdf

which uses a weighted average of hillshadings from four fixed directions.
The weight is squared sine of the difference between the aspect and each
illumination azimuth, emphasizing the darker slopes. The qgis code seems to
modify that a bit by making the four directions relative to the user
defined azimuth.

Is this a correct understanding ?

I am thinking about simulating this with webgl based (Phong) shading by
four directional lights.

-Andreas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20170408/b8defc36/attachment.html>