Physically Based Lighting Tools UE 4.23


I have been working on this blueprint tool set to make it easier for me to setup some physically based lighting in UE4 and I thought I will share it with the community, maybe it could be useful to people.


  • Light meter blueprint
  • Point, Spot, and Rectangular light blueprints with additional Luminance(cd/m2) unit added and some other features.
  • Sky blueprint with easy Sky dome setup, and some handy other features to setup PBL fast and easy.

I have made an extensive tutorial on the tools and how to use them so make sure to watch that first. In the tutorial I have some information about how it works and how its setup and I also show some things I discovered along the way. Here is the video link.

And you can download the tools here:…g7c0KZiW5nmogq

And here are some relighted scenes made with these tools. No fill lights or any other trickery is used. For daylight scene only the sky and the sun is used, or just the sky if it’s overcast scene. And for interiors no additional fill lights were needed, for the sci-fi hallway scene I used static emmissive set to some physically based high values together with my Lights BP tools set where the light sources are. I used GPU Lightmass for building the lights.


Let me know if this is useful to you, and any feedback on the tools is welcome.

I haven’t messed around with it too much, but it looks like your illuminance and luminance measurements are way off compared to doing the math manually with the Pixel Inspector. Also, changing the EV100 input also changes the illuminance/luminance, which is incorrect. You set exposure based on those readings, so it shouldn’t have any affect on them.

Hey. Thanks for the feedback. I assume you are talking about the Light meter blueprint. I have checked the Light meter values multiple times to the pixel inspector values, and they are not that far off if used correctly.

Of course I could not check the exact pixel, also the exact pixel that it measures is not that Exact so to speak. Because the way I made the Light meter was through a 2D capture component that renders to texture what the camera is seeing and then I measure the Luminance values of the textures pixels. I didn’t set the texture to be high res, so the calculations are faster, and so the exact pixel that the light meter is seeing is a couple of pixels in reality.

Also I had the problem of the Read Render Target Raw pixel node in my light meter blueprint ,not giving me results as the pixel inspector if the value was above 1.0 . It just gets capped at 1.0 So I had to do some math to actually get the correct result for the Linear Value based on those values that the node is giving me between 0 and 1.0 . And that is why the calculations are based on setting the correct EV100 **FIRST, **so that what the light meter is seeing is between 0-1 values.
I agree that it is somewhat illogical that the luminance and illuminance values change because of the EV100 but that is the only way I could have set it up, because the Read Render Target Raw pixel doesn’t give me values like the pixel inspector out of the box.

So if you change the EV100 and the indicator goes RED, then the calculations are not correct anymore, and you will get vastly different results than the pixel inspector. As for the Luminance and Illuminance values, The luminance is just the same value as the Linear Value, and the Illuminance is that value multiplied by PI, or if you press the calculate average button then the luminance and illuminance values are the averaged pixels values.

The whole reason i set this thing up is so that i can measure a part of the sky and get the average values, of what the camera is seeing.