Tuesday, March 10, 2020

Comparing Analysis Tools - Lighting Calcs

I recently started taking some time to better understand the Rhino ecosystem, particularly around analysis. Today's post shows my results from testing three ways to develop daylighting calculations for illuminance at a single point in time.

The tools used are:
  • Rhino + Diva
  • Revit + ElumTool
  • Revit + Autodesk Lighting

My example is based on the Diva tutorials found here. I downloaded the free sample Rhino model and then recreated the same model in Revit.

The assumption, for this study, is that each tool will achieve the same results if everything is setup correctly... and that turned out to be mostly true!
BTW, my friends at the University of Minnesota did a similar study about a year ago in preparation for their new lighting design minor; read about that here: Lighting Design at the University of Minnesota.

Keep reading to learn more...

Here are the metrics I used across all tests...

Material values:
  • Walls: 50
  • Ceiling: 80
  • Floor: 30
  • Furnishings: 20
  • VLT: 70

  • Space: 11’-9” x 26’-10” x 9’-2” 
  • South facing glazing: 39 SF

Other inputs:
  • Location: Minneapolis
  • September 21, 9am
  • Lighting bounces: 4
  • Workplane: 30"

Rhino + Diva

Rhino is a well known tool in the AEC industry, capable of creating complex and organic geometry. Diva is an add-in to Rhino and was originally developed by Harvard GSD, and is now distributed by Solemma LLC. Diva is capable of doing climate-based daylighting an energy analysis within Rhino.

Material Values:
Surface reflectances are assigned to each Layer defined within the Rhino model via this Diva dialog.

Other Inputs:
This Diva dialog allows the user to define the sky, day, time, light bounces.

Here are the point by point illuminance results.

Revit + ElumTools

Anyone who follows this blog knows I am a big fan of ElumTools, makers of AGI32. It is an add-in that provides a streamlined way to do lighting analysis completely within Revit.

Material Values:
Surface reflectances and Visual Light Transmission (VLT) are assigned by category; anything that is a wall gets a reflectance value of 50% irregardless of what material is assigned to an element; 'by material' is also possible and similar to what is shown later in this post for Autodesk Lighting.

Other Inputs:
In this dialog we can set location, true north, date and time, plus sky condition.

Here are the point by point illuminance results. The second image shows a schedule, created by ElumTools within Revit.

Revit + Autodesk Lighting

Autodesk has its own lighting analysis tool, which is a separate install and can be downloaded here. Be sure to install the latest version, which fixes some bugs and provides full support for Revit's new advance glazing material, which lists the VLT value!

Material Values:
Surface reflectance and VLT are assigned by material, as shown in these two Revit material examples. The second image provides sample RGB values for the list of reflectance values. There is  a little more to this, but this gets the idea across.

Other Inputs:
Within the Autodesk Lighting add-in we can verify the location and set the sky, day and time.

The results are shown here, within a 3D Revit view. There is an option to export point by point illuminance results/values, but that was not working for some reason.


The image below shows a composite image of all three results. They are all very close (notice the points are not aligned).  In the hot spot area there are a few numbers which vary a lot... not sure why as the adjacent numbers are pretty close.

When working with a Rhino model, we can achieve accurate daylighting results! Stay tuned for more examples of daylight autonomy and energy analysis study/comparisons.

Fun stuff!

Related posts:

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