SkyViewFactor Extension

Introduction

SkyViewFactor extension calculates the percentage of sky visible on surfaces of the SketchUp model. Sky view factor values can be represented as percentages of total sky surface or as a solid angle.
SkyViewFactor extension is oriented towards early project design phases, when level of details of future building is rather low, and when only basic information about building environment, position and geometry are defined.

Information about sky view factor for various building surfaces can influence important decisions related to building lighting and thermal strategies:

• Suggest position of windows on the facades, to provide more daylight inside building,
• Compare the effect of various sun protections alternatives on sky visibility,
• Suggest areas on the facade that should be studied in more details to prevent overheating or over-cooling of the building.

Sky view factor (SVF) on a point on the facade depends on building site environment geometry (relief, obstruction buildings) and on building shape. It is independent of the materials used on the facades or the interior spaces.

How To Use SkyViewFactor Extension

1. Open SketchUp model. Follow recommendations to prepare your model for DL-Light calculations.

2. Open SVF dialog from toolbar or menu option Extensions -> De Luminae -> Sky View Factor -> Activate extension and enter the calculation parameters.

   

   Fields description:

   • Project name - project name is used during export and for output filename generation. The SketchUp model name is used by default.

   • Results - directory where model will be exported for calculation.
     When calculation is started model geometry and resulting files will be saved in skyviewfactor_output subdirectory.
     For SketchUp projects stored on network disk (Windows), see Work on a copy of the model.

   • Analysis - Results represented by false color textures can have different meanings depending on selected value:

     • Percent [%] - Percent of sky surface visible form each sensor. Maximum value of 100% corresponds to an unobstructed horizontal surface. A vertical surface unobstructed has 50% SVF. When the sky is not visible the result is 0%.
     • Angle [sr] - Solid angle of visible sky portion. Maximal value is 6.28sr (2 Pi), and minimal 0sr.

     In trial version of the extension only 'Percent' option is supported. For more details read License information.

   • Details - Models may require different density of sensors. Level of details definition is directly connected to number of sensors or their density on surfaces. Big unobstructed surfaces may need lower level of details, with few sensors only, while smaller surfaces or surfaces with complex obstructions may require very high level of details. Level of details determines number of sensors for calculation, and has a major influence on calculation time and results accuracy.

     DL-Light allows to choose:

     • the sensor grid applicable by default to all calculated surfaces,
     • different sensor grids for some surfaces ("exceptions" button).
     

     See sensors selection for more information on the choices of proposed sensors.

3. Palette of false colours can be defined with precision. 3 options for palette are given, Automatic, Gradient and Custom:

   
   • The automatic palette is generated during calculation and is based on calculated results for selected surfaces. This is the best option for first calculations, when user doesn't have idea about possible resulting values
   • Gradient palette enables global palette manipulations - definition of minimal and maximal palette values, number of colors and start and end color. It is very useful once user have idea of resulting values, but want to experiment with colors.
   • Custom palette gives full freedom to add/delete/modify each color separately. Good for creation of final results for representation, when some surface areas should be highlighted for example.

4. After all data are entered in SVF dialog, select surfaces and press Render or button.

   

   Calculation time depends on number of selected surfaces, level of sensors details and model complexity.

5. When results are imported, selected surfaces will have appropriate false colors and Palette and Report dalogs will be opened.

   

6. Results analysis.

   • The Report dialog displays the distribution of results over current palette, and calculation input parameters.

     
     
     Note: An overall calculation of the mean and median of all calculated areas is available in the file “cumulative_results.txt” in the results folder.

   • Show/Hide Sensors and Values explores results directly in the model for each sensor.

     

7. For further calculations in the same model:

   • To run calculation on any surface simply select it and Render .
   • It is possible to modify the parameters of the calculation: to change the sensor density to improve the visualization of the results (for all the model or a specific surface), to change the units, to modify the palette of colors... Whatever the changes, use the Render button. Previously calculated surfaces will be updated with the new settings.

   DL-Light uses a calculation cache algorithm. It automatically detects if a surface requires recalculation or if a previous result can be reused. By default, the cache keeps the information of the last 10 calculations (value configurable in the preferences).

8. Archiving results:

   DL-Light allows to archive all the results of a calculation: reports, textures and calculation steps (exported Radiance model, weather file, ...). This archive can be reloaded on the model, subject to using exactly the same model as during the calculation.

   See the page Archiving results for more informations about this feature.

   • To archive the calculation results, click on the button Archive.
   • To load the results of a previous calculation, click on the button Load

   See the page Comparison of results for more informations about the comparison of archives.

9. Snapshots:

   Current SketchUp model view with imported results can be exported with palette or without palette to png format. To explore created images user can open folder where they are saved .
   This option is not supported in trial version of the extension (see license information).