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Exactly Emulating Real-Life Lighting Fixtures

I am a designer for an AVL (Audio - Video - Ligting) company. We design, install, and service theaters. churches and other large event venues. We have been using SketchUp to model spaces and show clients a 3d render of their current and new environments.

We are wanting to step up our game and use Unreal Engine to create more realistic environments.

The largest upside to UE is that we can put in “real” lights that mimic what we’re actually going to put in their building… spot lights look like spot lights, LEDs look like LEDs…

Most of the manufacturers that we use have IES profiles that we can use to recreate some of the looks of specific fixtures… but we want to take it a few steps further. We want to recreate the parameters of the lights as close as possible. Most manufacturers have VERY IN DEPTH information about the colormetrics and beam fallout and colors of their lights…

See THIS LINK from Chauvet:

https://www.chauvetprofessional.com/wp-content/uploads/2019/11/Ovation_H-55WW_Photometric_Reports-1.pdf

I am specifically interested in seeing if any of the information in the PDF correlates with any of the options in UE such as the attenuation radius or the inner and outer cone radius:

I can read the PDF and understand it… I can play with the sliders in UE, but how do I know if what I’m doing is accurate to the actual fixture?

Does anyone have any experience with this?

Thanks.

I had to model a light distribution with high accuracy once and used a spectral ray tracer for it. The result was imperceptibly close to the Rendering in UE with IES profile (in RGB - apples to apples) but that might not be true in general. Biggest discrepancies were indirect lighting effects.

Attenuation radius is not physically accurate, this should be a high value so the light follows the inverse square law.

Most of the parameters like intensity distribution and temperature and “cone radius” should already be baked in the IES profile so there is very little you actually can do to match it better.

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I do not know much about IES lights, but for the most accurate results, it is probably the best to use UE 4.27 and it´s pathtracer for checking, how it should look. Unlike the Raytracer, the Pathtracer does not take any shortcuts and delivers (not realtime) extremely accurate images.
Combine that with that option, that your IES light profile uses the IES intensity (as mentioned by @Speido ), and you should get a really good simulation.
And going by the manual, point lights and IES profiles seem to be the best combination, since Spot lights are not 360 degree lights, they work only for 179 degree cones, everything beyond that is cut off.

That’s great info. I was unaware that point lights and spot lights had different degree cones. It makes sense, of course, I just hadn’t thought about it.

We’ve been working in 4.26, but after this, we’ll probably move over to 4.27.

Thanks.