Interactive shading protractor in GeoGebra for Olgyays' stereographic projection

Shading protractor, as developed by Viktor and Aladar Olgyay, recreated as an interactive graph in GeoGebra.

To use the protractor, one first needs to create an equidistant solar path chart for a given location, for example using the Solarbeam application (solarbeam.sourceforge.net). This solar path chart has to be inserted as a background image in the shading protractor file, and the center and radius of the outer circle aligned with the solar path chart. Shading protractor currently contains an example of a solar path chart with 1500x1500 pixels, with image corners (1) at "LowerLeftCornerOfBackgroundSolarChart" (LLC), (2) at LLC+(5,0) and (4) at LLC+(0,5), so you can these settings for a new solar path chart to avoid repositioning the outer circle.

The protractor serves to illustrate shading masks for an overhang with side fins for a window with given orientation. Their defining points can be moved around freely in GeoGebra to observe how the shading mask changes accordingly.