Shading masks can be applied on a sun path diagram in Ecotect to visualize when a point will be shaded. This is useful for understanding the solar window – and can help you better understand exactly what’s shading your building from a particular vantage point, and exactly when it’s being shaded.

This page covers the “Overshadowing” section of the workflow diagram for Ecotect’s Sun & Shadow tools.

This video explains several ways to calculate the sun’s effect on your building using stereographic diagrams, shading masks, overshadowing, solar stress, and solar exposure.

Download dataset here (calculating.shadows.zip)

Shading Masks on a Point

Consider an imaginary hemisphere surrounding some point. Areas of sun blockage are determined by projecting lines out from this point each surrounding object. Then you can use a sun path diagram to plot where those lines intersect this imaginary hemisphere.

Any area of projected in red on the sunpath diagram represents an area of obstructed sky.

When the sun path for the particular location is overlaid, the designer can quickly determine, from a single diagram, both the times and dates throughout the year that the focus point would be in direct sun or in shadow.

Since this diagram was constructed with a point, the result is always a hard-edged shading block. The point is either in shade or it is not.

By assigning different colors to the shadows and reflections of different parts of you model, you can quickly see not only when a point or surface is in shadow, but what is actually doing the obstruction.

Overshadowing on Surfaces

Considering the overshadowing of a surface, like a wall, window, or roof, is more complicated than just a single point. There will be times when it is only partially in shade. Using Ecotect, you can easily tell exactly how much of a given surface is shaded (as a percentage). Rays are generated from the surface being analyzed and the number of rays per section that hit other objects in the model, compared to the total number of rays in that section gives the shading percentage.

A shading mask of the example same model as above, but calculated for a 2.5m x 2.5m horizontal surface centered at the focus point.

As an example, the window on the red building shown below is receiving shade, but how much?

This quantity can be measured by calculating the Sun-Path Diagram. In order to this, first select the object of interest. Then under Calculate, select Sun-Path Diagram.

Selecting the window in the 3D Editor.

The sun path diagram will now be displayed with an overlay showing the surrounding buildings. The initial diagram is calculated based on a POINT at the geometric center of the object. To more accurately calculate shadows over the entire SURFACE, select the Calculate Shading button. When you recalculate the Sun-Path Diagram your results will refresh themselves.

• Overshadowing Accuracy lets you adjust the level of precision. If a higher accuracy setting is selected, more rays are generated. High is a good setting.
• Decreasing the degrees of the Azimuth and Altitude in Sky Subdivisions can increase accuracy.

The Sun-Path Diagram on the left is what is first displayed (calculated on a point), while the one on the right was calculated over the whole surface.

The sun path diagram and the Ecotect project in the 3D editor are linked – so you can move the sun to a specific date and time in the 2D sunpath diagram and see its effect on the 3D model. You can also change the time and date by using the traditional drop downs in the menu bar.

As you move the sun to a specific time, a shading percentage is displayed. Black denotes 100% shade on the object and lighter shades of grey denote less shade.

On April 9th at 16:30 the window is 70% shaded.