Electric lighting in Revit example rendered in Enscape with custom light

Electric Lighting in Revit and Enscape Explained

In architecture, lighting is one of the most important design elements to get right. Whether natural or electric, proper lighting can make a space more vibrant and mentally stimulating. Therefore, lighting should be analyzed as much as possible during the design stages of a project.

This post will focus on developing accurate electric lighting (aka artificial lighting) using Revit and Enscape. Although this covers lighting in Revit, the same results (in Enscape) are also possible in the other supported design platforms; SketchUp, Rhino, Archicad, Vectorworks.
At Lake|Flato, we consider lighting in many ways, including:

  • Visualize daylight and shadows: Revit/SketchUp/Rhino + Enscape
  • Visualize electric lighting: Enscape
  • Visualize light in VR: Enscape
  • Analyze annual daylight (UDI, sDA, ASE): Rhino + Climate Studio
  • Analyze electric lighting: Revit + ElumTools
  • Physical analysis: building models in our shop

The image below, of the AIA COTE 2020 award-winning Austin Central Library, in Austin, Texas, USA, shows many of these techniques employed during design and construction.

Lake Flato Austin Central Library design example by Lake|FlatoAustin Central Library design by Lake|Flato

I have been involved in various aspects of lighting design and analysis for several years. Currently, I am the chair of the national Illuminating Engineering Society (IES) committee on BIM Standards. You can learn more in this BIM Chapters blog post: IES BIM Standards Committee.

The IES seeks to improve the lighted environment by bringing together those with lighting knowledge and by translating that knowledge into actions that benefit the public.

Illuminating Engineering Society (mission statement)

Revit light source types

There are two types of light sources possible within a Revit family: generic and photometric.

For generic, there are three light distribution types: sphere, hemispherical, and spot. These options are not based on any real-world lighting fixture. Early in a project, these may be used to imply electric lighting, but in most cases would ideally give way to a more accurate option defined next.

For photometric, the light source is mathematically defined based on light distribution as measured from an actual lighting fixture in a lab. The resultant definition is captured in an IES file. Revit can host these files and use them to define the light source within a lighting fixture family.

The following image is a section within Revit, with the lighting fixture’s Light Source sub-category turned on. Notice two fixtures have a photometric web (green checkmark), and two have a generic (red x) light source associated with them. Families with a photometric web will have a unique light source shape that describes the fixture's actual distribution.

Photometric IES files are available from most lighting fixture manufacturers. Either from their website or by request to one of their product representatives. It should be pointed out that there may be many IES options for the same catalog item based on an array of options. For example, lens options, power, LED count, color temperature, and more.

TIP: Once an IES file has been imported into a Revit family, the original file is no longer needed as the data is now embedded into the family.

Autodesk provides a folder with sample IES files, mainly for testing by new users, which should never be used. They are outdated and do not correlate to any contemporary lighting fixture available on the market.

Revit section with light sources visibleLighting in Revit 20 copyRevit section with light sources visible

Analysis ready lighting fixtures

The possibility of point-by-point illuminance calculations is an added benefit to developing Revit content to use accurate photometry. While Enscape cannot do this type of analysis, it can be helpful to appreciate what this means. Thus, I will share a workflow I use to verify light levels are correct for a given space and activity. This example will use a professional lighting analysis add-in for Revit, called ElumTools by Lighting Analysis, Inc.

Let’s look at the art wall example from the previous section. The second image below shows a partial section of a product specification, indicating the expected light levels in foot candles for various positions and angles.

Cutaway view highlighting light fixture are art wallCutaway view highlighting light fixture

Lighting fixture specifications exampleLighting fixture specifications example

Within the ElumTools Luminaire Manager, notice the information listed on the right, which was extracted from the photometric IES file; including lamp count, total lumens, color temperature, etc.

Lighting Specs_Page_30 copyElumTools Luminaire Manager

Finally, after reviewing surface reflectance values, a calculation is run, and the results are presented, as shown in the following image. Notice the meter readings in the center are 48 and 51 FC, which matches the manufacturer’s literature.

Lighting Specs_Page_34 copyElumTools calculated results

Here is an example of this lighting fixture family and the proper light source definition selected. It is important that the light source is positioned/aimed/rotated properly. The Emit from Shape option is not as critical as the Light distribution option, but you typically pick the one that matches your fixture and adjust the dimensions in properties.

Light source definition example in Revit familyLight source definition example in Revit family

Unfortunately, Revit does not extract the Initial Color (i.e., color temperature) or Initial Intensity from the IES file (like ElumTools did). It is important to set these manually so that they look correct in Enscape. The default values for a new lighting fixture family are not very bright, and the color is too yellow. This will have a negative effect on the overall quality of your Enscape rendering.

The following image shows the settings adjusted to match the data shown in the ElumTools image above (color temp and total lumens).

Lighting Specs_Page_42 copyRevit family properties within the project environment

Here is an example of how this fixture looks in Enscape. The time of day has been sent to nighttime to emphasize the electric lighting.

Tip: For SketchUp users, you can load an IES profile via the Enscape objects window by clicking Load IES profile (for specific tips on lighting in SketchUp, see Enscape Best Practices: Lighting In SketchUp).

Rendered example within EnscapeRendered example within Enscape

Free Enscape IES sample file

To demonstrate the many results possible with IES files associated with Revit families, you can download the free Revit sample file from Enscape via this link IES Light Gallery (19 MB zipped Revit file). Notice, in the image below, that the same three recessed lighting fixture families look completely different based on the IES file applied.

Comparing three IES files and their light outputComparing three IES files

Electric lighting always on in Enscape

Lighting is always on within Enscape. During daytime hours, electric lighting may appear off or washed out due to Enscape’s automatic exposure system. However, using Enscape’s Artificial Light Brightness slider, we can overpower these lights to make them stand out more. Notice the difference between the default setting and then maxing out the intensity.

Adjusted artificial light brightness in Enscape

Generic light sources

For custom lighting fixtures or something that uses a simple light bulb, the generic light sources are used to define the light source in Revit. In the image below, notice the simple lightbulbs within a glass dome. Notice Enscape is reflecting the light sources in the window glass beyond… which is a good reason to avoid trying to add this effect manually in post-processing (i.e. Photoshop).

Custom light fixture with generic light source. Image courtesy of Lake|FlatoCustom light fixture with generic light source. Image courtesy of Lake|Flato

Since Revit only allows a single light source to be defined directly within a Revit family, the use of nested families is required for this example. This makes editing the light source information, intensity, and color more challenging as the nested family must be opened and edited.

: Custom light fixture with multiple light sources defined with nested families

Custom light fixture with multiple light sources defined with nested families

 

 

The following image highlights the Light Source Definition settings and the material definition for the glass dome.

Nested light source family details

Nested light source family details

 

Emissive light sources

For any light source in Revit, the actual source is not automatically illuminated to indicate where the light is coming from. Thus, applying an emissive material, aka self-illuminating, will help for things like an exposed bulb, lens, or lampshade. The previous generic light source example also uses an emissive material for the lightbulb geometry.

If the glass dome were frosted, it may not be necessary to add the lightbulb geometry. It may not even be necessary to add the light source as self-illuminating materials not only appear to be a light source, they actually are a light source.

The next two images show the same light fixture with two Luminance levels selected for the self-illumination. Since this glass dome is not fully enclosed, it is still helpful to have the light source defined within it.

Custom light fixture dome with ‘dim glow’ illuminance. Image courtesy of Lake|FlatoCustom light fixture dome with ‘dim glow’ illuminance. Image courtesy of Lake|Flato

 

Custom light fixture dome with ‘Lamp Shade’ illuminance. Image courtesy of Lake|Flato

Custom light fixture dome with ‘Lamp Shade’ illuminance. Image courtesy of Lake|Flato

Additional reading

Check out this Enscape blog post: Best Practices for Emissive Materials in SketchUp

On a somewhat related note, you may find this post interesting: Calculating Light Levels for LED Strip Lights in ElumTools.

Conclusion

There are many ways to improve the realism of an Enscape rendering, including accurate grass, glass, assets, and even electric lighting described in this post. Each of these items are not particularly difficult to implement but can produce incredible results. These improved images will certainly impress your clients and project stakeholders.

 

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