Emissive texture illuminance

Hey community!

Ive been looking around for an answer to this scenario and have found a few different answers that dont quite figure out this dilemma. Ive posted them below:




These pages get me close to understanding. but no solution yet

Im trying to use emissive textures to illuminate a space. ive attached an image below.

Is there something im missing?

Thanks for the help!


If you are using baked lighting, you can can use emissive for static lighting.

If you are exclusively using spheres, I would use point lights within the spheres, and have the spheres not cast shadows.

Hey Zac,

Im trying to make the lighting dynamic, this is just a basic example showing the condition. Any other thoughts?

We also tried this route to no avail. Couldnt get the lighting build to complete.

Light Propagation Volume now works with Emissive Material!! - Rendering - Unreal Engine Forums!!=

This would be amazing if it were built into the engine! Alot of possibilities

Resparking the conversation here… Does anyone have any thoughts here? is this a bug? is this never going to happen inside unreal? or possibly in a future release?


Emssive materials do not dynamically emit lighting. They can if you are using Light Propagation Volumes for lighting, but that feature isn’t fully supported and a tacked on solution.

What are you trying to do exactly? There’s plenty of ways to fake lighting.

Hey Zac, Thanks again for your time. I work for a set design company and we are trying to pre-visualize lighting conditions. Except that we have very abstract fixtures, LED panels, etc. What drew me to unreal was the real time rendering aspect but this feature is very important to our work flow. Without it We cannot really understand what is going on in the scene. I know this is a very specific request, for a small part of the user base. Which is why im trying to get to the bottom of the situation :slight_smile:

For example. if we wanted to run a chase sequence down an LED strip. It would be more efficient to run a media player with and emissive texture on a mesh than to make 150 +lights in a row. Currently there is no illuminance on other material. I will look into light prorogation volumes a little more deeply today.

BTW, super happy about the media player updates in 4.18!

What I would do is use VXGI–it’s a fully dynamic lighting system that can use emissive textures, it’s not as accurate or as high quality as the baked lighting system but it sounds like it would be the only option for what you want to do. To use VXGI quickly though you’ll need a more powerful computer with a good GPU.
You can check out the thread on getting the VXGI build of the engine here: NVIDIA GameWorks Integration - General Discussion - Unreal Engine Forums

Darth. This looks like the direction I want to go! Super appreciate this :slight_smile:

Continuing this conversation. After researching this topic I now understand that this integration takes a level of understanding in software development. It seems as if this option has been available for quite some time, since 2014 if im not mistaken.

Im extra curious, Is this feature ever going to be integrated into the engine or is it such an abstract application that it will never make past the development stage?

The reason I am asking is because it is so necessary for us in our studio, that we will either figure it out the long way or potentially wait for its future release. Im hoping for the latter.

Thank you all for your time again. It has been most valuable.

VXGI is Nvidia technology. I guess it’s never integrated engine by Epic. But it’s updated by Nvidia so if you need it then just use it.

VXGI won’t be made a part of UE4 by default, what could happen in the future is that Epic could make their own dynamic lighting solution–they originally had one called SVOGI but removed it because many devices (like the Xbox One) aren’t powerful enough to use it. VXGI is better than SVOGI but still has a performance impact so it’s just a matter of technology moving forward.