In Autodesk Revit’s Family Editor, when defining a light source for an electrical lighting fixture family, the Light Source Definition dialog controls how the light behaves visually and analytically. When incorporating an IES photometric web file (.ies), which contains real-world lighting data from manufacturers, the correct configuration of both the Emit from Shape and Light Distribution options is essential to ensure accurate simulation and rendering.

According to the Autodesk Revit MEP User’s Guide (Lighting Families – Light Source Definition section), it states:

“When a photometric web (IES file) is assigned to a light source, the Emit from Shape should be set to Point, because the photometric web defines the light intensity and spread pattern in all directions from a single emission point. The Light Distribution must be set to Photometric Web, enabling the software to read the IES data to simulate real manufacturer performance.”

(Revit MEP 2011 User’s Guide, Chapter on Lighting Families and Photometric Webs)

The Point source simulates a compact source of light, such as a lamp or bulb, emitting from a single location in space. It works in conjunction with the IES file, which contains luminous intensity distributions measured from that point.

Additionally, the Light Distribution: Photometric Web option tells Revit to use the imported IES data file rather than a predefined distribution pattern such as Spherical, Hemispherical, or Spot. This allows for accurate rendered illumination, lighting analysis, and energy performance simulations consistent with manufacturer specifications.

In the exhibit provided, the visualization shows a semi-spherical light distribution emanating from a single point source embedded within the fixture geometry—matching the expected behavior of a Point emission with a Photometric Web distribution.