Nvidia RTXGI Plugin used to light the scene. Only emissive light sources in this scene.
Nvidia RTXGI Plugin plugin used to light the Unreal Engine scene. Only emissive light sources in this scene.

I am showing up a little late to this party, but Nvidia has finally released official version of the Nvidia RTX GI Plugin in the Unreal Engine Marketplace. Well link to external site rather, which leads to Nvidia’s site right here. You will needNVidia account to be able to grab this. But if you are using NVidia card, chances are you already have one.

Unreal Engine 4.7 RTX GI plugin in Unreal Engine Marketplace.
Click the External Link will take to to the page where you can grab the plugin.

Now, the premise of this is fascinating to say at the least. Unlike Lumen in UE5 this is purely hardware based, so it’s fast. It will require capable hardware as expected, but the results should be similar or even more crisp than what we are able to see with UE5. Finally we will be able to get realistic real time GI, colorful surfaces bleeding light to others, emissive light sources, well being actually emissive and so on. This gives us that sweet baked light look but without baking.

Installation

Let’s take a look how to get up and running with this. So head to the Nvidia’s site here, and grab the plugin. You need to login and click to “Agree to the Terms of the NVIDIA RTX SDKs License Agreement. And you should be able to download the RTXGI_UE4_Binary_Plugin_v1.140.zip.

Here you can download Nvidia RTX GI Plugin
Nvidia RTXGI Plugin plugin can be downloaded from NVidia

This will require DXR Capable GPU Windows 10 and such. And Unreal Engine 4.27. Please make sure you have those.

Make sure you have closed Unreal Engine before proceeding. Then go Unzip the archive and copy the complete RTXGI folder to Epic Games\UE_4.27\Engine\Plugins\Runtime\Nvidia.

Now when you open Unreal Engine, you should get popup on the down right about new plugins. Check “Manage Plugins” and make sure the plugin is marked as Enabled. If it is, the plugin should be installed correctly. Before the fun begins, make sure

Now when you open Unreal Engine, you should get popup on the down right about new plugins. Check “Manage Plugins” and make sure the plugin is marked as Enabled. If it is, the plugin should be installed correctly. Before the fun begins, make sure default RHI is set to DirectX 12 and Ray Tracing is enabled. If this is a new project, restart and the sometimes lengthy shader compile is necessary.

Using the Nvidia RTX GI Plugin

Next we need to fire up the console and throw the following commands at it:

r.GlobalIllumination.ExperimentalPlugin 1 to enable global
illumination plugins (this can also be set in .ini files, or in blueprints).

r.RTXGI.DDGI 1 to enable RTXGI (set in .ini files, on the console, or in
blueprints).

It is good to enable log view from the Window / Developer menu, in this way we can confirm if the GI is really enabled.

Now the engine should be ready for some fantastic RTX GI action. Yay!

Placing DDGIVolume to the scene will work a bit similarly as PostProcessVolume. They contain a grid of probe points that RTXGI will update using Ray Tracing. The DDGIVolume contains related settings that can be adjusted.

Here is what I was able to come up with five minutes of playing with it.

Nvidia RTX GI Plugin in action
Nvidia RTX GI Plugin in action.

Neat, I say! I placed a spotlight on the middle, shining the light in middle of the purple and white wall. You can see that the bounce now light casts colored light to the right side floor.

At the furthest point you can see emissive cube casting light, and shadows behaving believably way. Also there are no seams. Really, seriously. No seams between modular walls. There used to be a lot of tweaking required when baking modular walls, to get rid of the seams even when the modules were correctly snapped to grid. I welcome this.

If you used a template with static directional light, sun or skylight, and want to change scene to fully dynamic setup it maybe necessary to build lighting to be able to see the new settings in the scene.

It is worth mentioning that currently RTXGI lighting does not work with UE4’s other ray traced effects (for example, ray traced reflections). So Lumen implementation may have edge here although for what I have seen the reflections are not quite there yet either.

We can adjust the probe counts as well as many more useful settings in DDGIVolume. I am planning to return to this topic.

Nvidia RTX GI Plugin
In this example I increased probe count to 13,13,13 and this helped to remove some of the splotching on corners of the room.

With probe counts it is better to keep the count reasonable, otherwise this will cause instant crash but on the other hand too low probe count can lead to splotches or artifacts in the corners.

I will make more in depth tutorial on DDGIVolume settings in near future. At this point I think there must be very few people who know what each of them means. But let’s keep digging!

The video tutorial is now up in Youtube.