Explain Like I'm Five

So in the real world, light obeys all kinds of laws of physics. Photons, which are particles and waves simultaneously somehow, are emitted from a light source, travel in straight lines until they encounter some matter then they either bounce off, are absorbed and re-emitted. Our eyes fairly precisely detect the number and wavelength of photons coming from the direction we are looking, which allow us to glean information about what objects are out in the world.

Simulating that with a computer takes a lot of math, because you would have to simulate the paths of a LOT of photons. For a very long time, computers, especially ones consumers could afford, just couldn't do that, especially not in real time for video game graphics.

So through the 90's and 2000's, video game developers developed shortcuts for creating reasonable approximations of lighting effects. These are a pain to figure out how to do but they look reasonable and run much faster than trying to do the lighting physics. By and by graphics cards started coming with circuitry specifically to pull off these shortcuts, and small programs designed to run on graphics cards to apply these effects to graphics are called "shaders." You may have heard that term if you've been around gaming for awhile.

Ray Tracing is the technique of doing the actual optical phyiscs problem to render the graphics instead of using those shortcuts. Like I said earlier, there is a lot more math involved here, but since you're simulating the laws of physics you can get much more realistic lighting effects this way.

Things like Pixar movies or Final Fantasy: The Spirits Within used ray tracing techniques for rendering the animation in the movie with realistic lighting, but these took minutes or even hours to render a single frame. It's also how the graphics in Myst and Riven were made, during production they ray traced the graphics then stored the results as pictures which a home computer of the time could easily display.

More recently, starting with Nvidia's RTX-2000 series graphics cards, publicly available hardware is capable of doing all that math in real time, allowing for video games to have very realistic lighting drawn by the game engine in real time. This promises two things:

1. Better or more realistic lighting effects than possible with shaders. Things like shadows falling on your character's gun, or everything in the environment that glows casting pools of light and shadows. This has been realized to a point, though there is still more computations to do so it does run slower, when you turn ray tracing on it usually comes with a decrease in frame rate.

2. Easier development. I'm not sure this has actually been achieved yet, but theoretically once your game engine has ray traced lighting effects built into it, you should be able to design your scene, populate it with objects and light sources, and it should just work. Problem is there are still so many graphics cards out there in use that either outright can't run real time ray tracing or do so very poorly that they still have to use the older shader approach, so in practice it has actually complicated not simplified game design.

Light go boing.

ray tracing mimics the way light bounces around on surfaces in real time. it does this by tracing rays from light sources in game and colouring the objects they hit. the rays then "bounce" off of the objects and redo the same step of colouring. this needs to be done for every pixel you can see.

in regards to it changing video games: idk, how much do you care about lighting?

Ray Tracing I believe is the CEO of GeForce.

If you want pretty graphics this is good.

If you want many frames this is bad.

It's a lighting technique that creates more realistic visuals, especially reflections.

The technique allows the GPU to "track" / calculate how the light should actually travel and what it bounces off of (like light in real life), compared to the pre-calculated methods of before.

So it will cost you processing power and therefore frames, but it greatly increases the visual accuracy of lighting, shadows and reflections.

A simple but effective example is Minecraft with Ray Tracing. The following video showcases the difference:

https://youtu.be/9qxfavtUs7w?si=pBSq7iysC0HvHoYz

Notice how the game looks completely different. That's what lighting can do for a game.

Obviously this is less noticeable when it's a game with realistic graphics and a lot of time spent on getting the (prebaked) lighting just right.

It's a hardware intensive process that tries to make lighting as realistic as possible. So, which areas are illuminated, which are in shadow. From an artistic perspective, this is very important to how a user visually processes any particular image.

No, not really. Just better graphics.

Games need to figure out what color to show for each pixel on the screen. Imagine shooting lines out from your screen into the game world and seeing what objects they run into. Take whatever color that object is supposed to be and put it on the screen. That's the basic idea.

To make it look better, you can repeat the process each time one of the lines hits an object. Basically, when a line hits an object, make more lines -- maybe a hundred or a thousand or whatever the programmer picks -- and then see what those lines run into as they shoot out from the point in all directions. Mix the colors of the objects they run into and now that becomes the color you put on screen.

You can repeat that process again and again with more and more bounces. As you add more and more bounces it gets slower though -- since there are so many lines to keep track of!

When you've done as many bounces as you want to do then you can shoot out lines one last time to all the lights in the game. If there is an object in the way blocking a light, the color for the object you're trying to figure out will be darker since it's in a shadow!

It's an old and simple idea to figure out what color something is like that by bouncing off objects repeatedly... but it's hard to do quickly. So, most games until very recently did not work that way. They used other clever tricks instead that were much faster, but made it hard to draw reflections and shadows. Games with those other techniques usually did not look as good -- but you could actually play them on old computers.

I always disable it because it makes games looks weird. I refuse to believe it's realistic lighting