Rorschach Shadow Diagram Implementation

Here’s a look at the implementation of the Rorschach Shadow Diagram, an overshadowing metric we’ve developed to improve legibility and quantify our shading studies. The first post presented its concept while this post demonstrates its application.

The case study here analyzes horizontal shading on a northern facade in Sydney, Australia. As it’s south of the equator, the northern wall receives substantial solar exposure throughout the year. The question for this study was simple: how far should we project a horizontal sun shade to reach a target percentage of shading during the year? Using the Rorschach metric, we can quantify the percentage of the year a point of interest is in the shade (our point of interest is at the bottom of the wall in this case).

This is a quick way for us to study daylight exposure before moving into more rigorous simulation (like solar irradiation, daylight autonomy and thermal simulation). The Rorschach shadow diagram is purely geometric, so it’s not the answer for comprehensive analysis, but it proves to be helpful for early schematic design.

We’ve attached a definition below for others to use and the above video shows a demo of the file. Quick note: in order to make the file generic, we made a grid to pixelate the diagram, so increasing the diagram’s density will increase accuracy but slow down calculation time. Enjoy!

Obligatory disclaimer: the author does not guarantee that these parametric models are bug-free or that they will solve all of your problems. If you find bugs or have suggestions for improvements, please let us know.

[download id=”23″]


  • Mostapha

    This is awesome! Do you guys mind if I shamelessly copy this technique and apply it into next version of Ladybug? I will definitely reference to lmnts, this page and your script.

  • ekatzenstein

    Thanks for your interest Mostapha! Our research is done under Creative Commons, so feel free to use the diagram with your plugin provided you reference Tech Studio. Also, you may want to link to our previous post ( since it gives a bit more info on the concept.

  • Mostapha

    Nice! I added Rorschach Shadow Diagram to the issue list: ( I’ll make sure to double check how I reference to your work before the public release. Thanks again.