Synopsis

Shading masks allow you to determine the extent of overshadowing for selected objects on a sun-path diagram. This tutorial explains how to create a shading mask within Ecotect.

Duration

You will need about 15 minutes to complete this tutorial.

Training and Accreditation

Successfully completing this tutorial fulfills one of the practical skills required for completing Level 2 of the Shadows training module.

Resources Required

To complete this tutorial, open the 'ShadingMask.eco file located in the Examples folder of your Ecotect installation.

Tutorial

1. In order to create a shading mask, you will need an Ecotect model that replicates the objects you would like to examine for overshadowing. The example Ecotect file presents one common scenario, where the site adjacent to the proposed development cannot be overshadowed by more than 50% at 12 noon of the Winter Solstice.
2. Select the plane object that represents the site adjacent to the proposed development. Go to the Calculate menu and select the Sun-Path Diagram... menu item.
3. A stereographic projection of a sun-path diagram for the site opens in a new window. Projected onto this is the approximate extent of overshadowing caused by the proposed development. However, this can be quantified further by creating a shading mask.
4. Before we create the shading mask, first check that the time and date are correct for the day you wish to analyse - this appears in the bottom left hand corner of the sun-path diagram. If not, click back into the Ecotect window in the background, change as required, and the sun-path diagram will update accordingly.
5. To the right of the sun-path diagram, click on the Shading Mask tab to expand it. Note that Ecotect tells you which object you have selected (No. 170 in this case). Click the padlock to lock the shading mask to this object.
6. Click the Calculate Shading button, and the surface shading dialogue box appears, where you can configure the settings used to generate the shading mask. Firstly, specify the Overshadowing Accuracy. The Use Fast Calculation Method checkbox is mainly of benefit when working with large, complex models, but you can leave it checked for this model. The slider below this increases the number of test points used. Naturally, the higher the accuracy, the longer it takes to perform the calculation.
7. The Sky Subdivision allows you to specify how many segments the sky dome is divided up into. The smaller the subdivisions, the more refined your shading mask will be (again, this will increase the calculation time).
8. Next, Displayed Data. We're going to use Overshadowing Percentage, but Ecotect can also display this data in other ways, such as direct solar stress. No need to check Show Total Annual Values.
9. Last, specify how Ecotect generates its calculation points. Randomise Surface Points produces more accurate results for highly detailed site geometry. For this example, leave Check both sides of Surface unchecked, as only the top side of the plane object is exposed to the sun. And finally, check the Display Test Points checkbox - this shows you the test points used as little green dots on the Ecotect model.
10. Click Ok. After a short calculation period (depending on the settings you used), Ecotect displays the shading mask on the sun-path diagram. Using the legend to the right of the sun-path diagram, the darker areas of the shading mask represent those points of the site which are in shade most often throughout the day. In the bottom left hand corner, you can see the shading mask expressed as a percentage value of the site. You can also see individual percentage values by checking the Show Percentages checkbox, however you will need to zoom in on the sun-path diagram to see these values clearly (and possibly use a less refined sky subdivision).

Tips

• If your shading mask is completely black once the calculation is complete, check the direction of the surface normal for the object. The surface normal should generally point outwards and up towards the sun. The keyboard shortcut Ctrl+F9 displays surface normals in the 3D editor window. To change the surface normal direction, select the object and use the Ctrl+R shortcut. Press F9 to turn them off again.
• Topography of the site can have a significant impact on the overshadowing percentage, especially for steeply sloping sites. Try to model the terrain as accurately as you can.