Shadow Angles Applet: Models the relationship between location, solar position, surface orientation, tilt and shadow angle. This is an interactive applet so you can adjust the sun position by clicking and dragging it with the left mouse button or use the middle and right buttons to pan or rotate the view.


The aim of this applet is simply to demonstrate the how horizontal and vertical shadow angles change with different dates, times and location, as well as the orientation and tilt angles of the surface. The vertical shadow angle is critical to the design of shading as it determines the required projection length. This is shown as an angled plane drawn directly from the bottom of the shaded surface. An example horizontal shading surface is then projected out to this plane to clearly show the shading requirement.

To experiment with this, interactively drag the model nodes to change orientation, tilt and date/time, and watch the vertical shadow angle and shade depth as they update dynamically. Alternatively, use the sliders around the edge to interactively change the date, time and location. The left, middle and right mouse buttons allow you to zoom, pan and rotate the 3D view, and the buttons at the top allow you to adjust display settings.

Display Options

You can use the OPTIONS button menu (F4) to change the main display settings. This menu lets you toggle overlay panels that show solar information, the world map and simple instructions. You can also use it to change the size of the world map, overlay world time zones or select different views of the model.

Using the Display Options… menu item (F5), you can determine what components of the sun-path diagram are displayed and how they are shown. This allows you to tailor the image to suit your particular demonstration or application.

The only real way to understand the use of these applets is to experiment, so please feel free to simply play about with it.




Josh 19 February, 2013 - 04:18


Great little applet. I’m wondering: any chance you might be able to suggest a good reference (link or book) from which I could get the formulas to calculate VSA and HSA?



Guest 10 April, 2012 - 17:35

I installed an awning in the back of my home which faces south west. The software is great but I don’t know what the tilt angle means… Building are built using 0 degree tilt.

I am a little confused by the light shadow that appears on the ground and what that is… and I’m also confused by the little roof for lack of a better term where it shows 0.YYY x h… and what that means…

So if I have an awning that sits up 9’ off the ground… and it extends 9’ out… how much shade can I expect and where using this tool…

My co-ordinates are 43 Latitude and -80 Longitude…

Any help would be great.

Sathyanarayan 1 February, 2011 - 05:48

I really liked the software.

Alkmini 12 May, 2010 - 16:42

Thanks a lot that was really helpful. I was trying to find something similar over a month :)

Athens, Greece Alkmi

Wichai 16 April, 2010 - 15:43

I likes this software a lot… Thanks, Wichai - Thailand

Olivier 10 March, 2010 - 16:46

Andrew, how does this (VSA + HSA) relates to the calculation of the Effective Shading Coefficient attributed to a shading device? I understand SC relates to the ratio of solar gains through the referenced 3mm single pane of glass; so would you need solar data to actually compute the ESC of the shading device?

Olivier 24 February, 2010 - 16:39

Andrew, Strange thing: when you zoom in the graph using the scroll wheel of the mouse, it works as expected, but zooming out revert to scrolling down the page… uhmmmm… a setting?

Olivier 24 February, 2010 - 16:42

…nevermind… I found it… Shift+Right-Click, like with Ecotect… I should have known…

Dr. Andrew Marsh 28 February, 2010 - 18:58

Hi Olivier,

You can also zoom using the Left mouse button. Just click somewhere there isn’t a node or GUI element and drag up and down to zoom in and out.

The page scrolling instead of zooming with the mouse wheel is browser-specific. Firefox and Safari seems to work really well whereas IE, Chrome and Opera either always page scroll or change to that when you zoom out. Not sure how to get around this which is why I added the left-click up/down option and the Shift+Right-click.

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