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I need to create image-raster with shadow of relief and shadow of buildings in one. I know how to create shadow of relief but how i can create shadow of buildings with r.sunmask? I dont know how from 2D polygon layer of buildings create shadow of complete buildings.

underdark
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THERimania THERimania
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1 Answers1

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You need to run r.sun, not r.sunmask for this task. There are also convenient GRASS GIS addons to run it in hourly or daily mode.

You first need to extrude your buildings with v.extrude, then run the solar computation. See for extrusion "Extrude 2D polygons to 3D" and for a shadow example here.

enter image description here

(image courtesy: Markus Neteler)

enter image description here

(image courtesy: Vaclav Petras)

markusN
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  • Hi, does this take the topography into account for computing the shade? – Louis Dec 05 '23 at 15:06
  • Yes it does. Above surface includes the topography and the buildings, put together (I am not the author). – markusN Dec 06 '23 at 16:25
  • Thanks for answergin @markusN – Louis Dec 15 '23 at 17:49
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    I can't install r.sun.hourly, can you help me here : https://gis.stackexchange.com/questions/471645/install-grass-missing-addons-within-qgis ? thank you – Louis Dec 15 '23 at 18:52