RTX vs Lumen – Unreal Engine 5


I’m going to have to do a bit of learning with this one. What precisely is RTX Raytracing? I’m familiar with Lumen but this will be a bit of an adventure, because I’m going to have to do a bit of research. I know that RTX Raytracing is a more standard, baked lighting system, and Lumen is the new dynamic Global Illumination system in Unreal Engine 5, but I don’t know much more beyond that.

[And right off the bat I was wrong, RTX Raytracing is NOT baked illumination, it is dynamic illumination. My apologies.]

Before we get started check out our article on Lumen, we go in depth and you get the full story on Lumen, raw and pure.


So after watching this thing, I’m still not really sure, this guy didn’t really educate me too well. It looks like Global Illumination is going to be a game changer, for hardware as well as software, commonly utilized features of the new line of Nvidia cards will not be needed anymore.

Raytracing will be what you use when your GI takes up too much processing power and you need to cut corners.

[Once again, please note, this is very wrong, look grasshopper, as you study a bit and learn, you will understand that Raytracing is NOT something you switch to when Lumen is too demanding. Raytracing is used when you want to apply extra processing power, to make your lighting more beautiful than lumen.]

So let’s breakdown each of these and get into definitions.

What is ray tracing good for?

Is Lumen the same as ray tracing?

Lumen is a type of raytracing, but it uses more generalized hardware than RTX. Raytracing is more costly, and gets more beautiful results.

Check out this article on RTX Raytracing from the elite at Nvidia.

What is Lumen?

Lumen is the Global Illumination system of Unity. You can develop your games with illumination at runtime instead of baking your illumination constantly which is a pain and a chore. One that has plagued game developers since the days of yore.

Do you remember when the dualshock controller was developed for playstation?

Some of my readers were only born around that time, but until then, game controllers all uses 4 single buttons to move their characters around, there was no partial movement, you were either moving up down left or right and you were either going fast or not moving. So when the new controller was developed, it was a revolution. 10 years of uncomfortable controllers were finally replaced with a smooth system of movement, comfortable controllers. This is how it feels to me. Oh you mean the task I had to repeat 500 times is now automated, and I don’t need to do it ever again? Ok, makes sense.

It was very nice moving the lighting around that dark neighborhood, and lighting up all the cars and trees. It was shiny and fun, I liked moving the light through the trees and seeing the leaves all rustling through the shadows.

It is a really nice feature for developers, and will also make for better quality games, but most of the fun of this new technology is on the developer side, which is squarely where it should be for the Unreal Engine 5. Playing games is dead, there is no point anymore, Unreal Engine 5 is here. It is more fun and more rewarding to make your own games than it ever was to play them. If you’re not making games, you’re doing it wrong.

That doesn’t really explain Lumen.

Lumen just lets you move lights around, and it will update naturally and realistically, without having to move a light into position, then click bake, wait about 5 or 10 minutes, and then when you’re done you see the result, and then move it again cause it looks wrong…. Then bake again, wait 10 minutes, move it again…..

The Unreal Engine 5 developer on the other hand is just moving his light around 3 or 4 times, it takes a few seconds….

What is RTX Raytracing?

Ok, after researching it, it looks like RTX Raytracing is a new lighting system as well, build around the new RTX Series of cards. Oh I see what that guy meant now, if you’re using Global Illumination for everything, this RTX line of cards becomes a lot less useful.

It has multi bounce indirect light with no bake times, very nice, it has lots of indirect light, approximating reality, without a whole bunch of processing power being required.

It can handle millions of dynamic lights at the same time, whether indoor or outdoor, without baking.

Nothing special required, just go into the project settings and enable it.

It works in Unreal and Unity.

Which is the winner?

I think it’s pretty obvious which of these I prefer, actually, they both sound very nice. RTX Raytracing also removes the requirement to bake lighting. So this becomes a more complex battle than I had initially suspected….

Well for one thing, Unreal Engine 5 allows for Soft Raytracing, so both can be enabled.

Which solves that. Actually it’s kind of a mixed bag. RTX Raytracing is more beautiful looking, but it has worse FPS performance. Essentially your problem breaks down to this:

Do I want worse performance, for more beautiful lighting, with RTX Raytracing, or do I want light calculated at a fraction of the performance cost, but it’s not as nice looking. Or do I just want to enable both and have really unusually beautiful lighting with performance at cost plus a fraction of a cost.

That actually seems like the best option available. But if you need to cutdown on overhead, you can favor Lumen as the fast an economical option.

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What am I going to use?

Overall, I am going to be going with Lumen. I have worked with Lumen and found it powerful and impressive. I did not run it on my RTX series card because I don’t have one. I am outside of the demographic targeted by the RTX Raytracing crowd. I guess it doesn’t matter that much if RTX Raytracing is nicer than Lumen, I’ll be using Lumen.

Final thoughts

So basically it becomes an overhead issue, does this hardware have the ability to run RTX Raytracing comfortably without dropping FPS, crashing, etc. Also the hardware requirements for RTX limit the range of options for potential hardware to only the Geforce RTX series of cards, making it less useful in a generalized marketplace. Beauty is a factor in this equation, you need to decide if the extra visual flare is worth the development overhead, FPS drops, potential for crashes, etc. How are you going to max out your game, basically. Do you have room in your budget for RTX raytracing or would it cause too much slowdown.

Conversely, Lumen is a nice generalized system that produces RTX raytracing like quality at a fraction of the cost. It is a good system if you want your game to run well, and over time, and this part is key, Lumen will eventually fully displace and replace RTX Raytracing, as the system improves, you will no longer need RTX, nor will you get better results in it. Lumen is the future in this regard. If you want to future proof your game, go with Lumen, if you want the nicest results possible, and don’t care that non RTX cards can’t run it, go with Raytracing. You could even just go with both.

So what do you do?

This actually makes me sit and think about how happy I am to be developing games right now. The technology has gotten so good it’s just jawdropping. I still remember playing on my NES entertainment system as a boy, playing mario 1. In 30 years gaming has advanced to a mindblowing level of power and potential, i can now make games more beautiful to look at than anything I ever played growing up.

It is so much fun to make games, and the stuff I have to work with is just so cool. I am putting scenes in my game that look like stuff out of the best of the best AAA content. Some of those scenes are so beautiful they’re almost impossible to comprehend, and they are a part of my game, in a sense they belong to me. I own those scenes, and I can make my games with them. There’s this beautiful city I’m building, with a cool set of slums, and all kind of shady business going down there. Dark Alleyways, shopping districts full of shops, a big sci fi quadrant. It’s professional grade environments, and I’m just some guy. It’s really something. I can only imagine what game design will be like in another 40 years, when my wife is 60 and I am 76. It will be very unusual and awkward navigating this technological wonderland. There will be a kind of buddhistic sense of humor to watching my own generation, wandering around as elderly people, confused and scared by the world, as they begin to fall, literally and metaphorically. As I just smile and laugh, with a good handle on the new technology that now confuses them. When my time comes to go, I think I will be chuckling.

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