What is lightning tracking and should you care?


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Incredible lighting, but will it be worth it?

By Whitson Gordon

[Editori’s Note:] Some of the first concrete details about the next generation PlayStation (let's call it PS5) were revealed yesterday, and in that revelation the "ray tracing" was specifically called as a feature that the new GPU could handle. So, what is ray tracing? We hope the article below illuminates (ha!) This technology a little for you.

The new RTX line of Nvidia graphics cards is coming soon, and this time they offer more than just the typical performance increase over the previous generation. RTX GPUs are the first consumer GPUs capable of performing lightning screening in real-time, which is an impressive advance in 3D graphics, since in theory it makes games look more realistic than ever. Let's take a look at what this technology really is, why you should care and why it is still very difficult to make even this new hardware work.

Real-time radius tracking demonstrated in Battlefield V at an Nvidia press event.

Real-time radius tracking demonstrated in Battlefield V at an Nvidia press event.

What is lightning tracking?

To understand this new technology, it helps to take a brief look at what preceded it. Modern videogames have long used a technique called rasterization to generate the image on the screen. The way it works is your computer looks at a 3D scene and calculates the distance from certain objects, where light is coming, and what objects are in front of others. Using this information, it determines which color each pixel should be on the monitor, drawing the scene point by point as a 2D image.

Over time, developers have greatly improved this technology, giving objects the ability to design basic shadows based on light sources, or using tricks such as ambient occlusion to add extra shadows regardless of light sources. But most games do not truly Simulate the way light behaves in the real world – they counterfeit it with one technique or another – making it difficult to generate truly realistic shadows and reflections. (That's why you rarely see mirrors in video games, and when you do, the images inside them are usually very crude.)

Ray tracing is a rendering technique that aims to simulate how light is reflected by objects, creating shadows, reflections and more realistic lighting effects. In an interview with Gamers Nexus, NVIDIA's Tom Peterson described it as a physics-based way of creating images, as opposed to artistic way to create images.

In the real world, a light source – say, your bedroom lamp – produces photons that jump around the room until they reach your eye. Ray tracing performs this process in reverse, tracing the individual "camera" rays of the scene and tracking how each ray intersects different objects, projects shadows and reflections, and returns to the light source. This ensures that the computer is not wasting processing power on objects the camera does not see while still producing much more realistic lighting effects. Disney did a great video explaining this process for path tracking, which is similar to ray tracing, which we show in the GIF below.


You can see a visual explanation of this in the Disney Practical Guide to Path Tracing, shown in the above GIF.

This technique has existed for many years and you see it countless times in movies with special effects generated by computer. Hollywood uses rendering farms to calculate ray tracing for scenes, as they are working with huge data sets and making a large number of rays for entire scenes. It can take hours or days to render even a short scene in a CG movie that uses ray tracing. In the past, the amount of calculations required made it impossible to make video games, as this needs to be done in real time so as not to affect the gameplay.

So what's special about RTX cards?

Lightning tracking can be commonplace in Hollywood blockbusters, but these effects are created in expensive render farms, and even then it can take hours or even days to render a single frame because of the complexity of it. Computer games, on the other hand, need to be rendered on your home PC in real time with hope of 60 frames per second. This means that advanced lighting techniques like this have never been easy to implement. In fact, when IGN first shared the initial demonstration of Nvidia with GDC's Ray Tracing, one commenter noted, "It's a good demonstration, but this illumination is not possible in real time on currently accessible PCs, it's probably going to be 5 to 10 years though ". This demo was running on four Tesla V100 GPUs, and at last week's event, Nvidia showed that it was running on an RTX Quadro board. Of course, a Quadro is still six times the price of the RTX 2080 Ti focused on games, but it's a huge step forward in an extremely short amount of time, and the fantasy of tracing real-time lightning being possible at home is approaching a lot to reality.

Nvidia's new GeForce RTX family of GPUs are the first consumer-focused consumer graphics cards to support real-time ray tracing … with some captures. These cards make use of what NVIDIA calls the "hybrid rendering model" that combines ray tracing with rasterization techniques, thanks to dedicated RT cores designed to calculate the intersection of each radius. It also uses special non-noise algorithms and dedicated artificial intelligence hardware, called "Color Tensor," to reduce the number of spokes that need to be tracked. In other words: they are still cheating a bit, since these cards do not scratch the whole scene in real time, but the results are a significant advance.

It should be noted that at this point it is not clear whether all games will use the RT and Tensor cores to do these calculations. The slide below shows how Nvidia introduced its new rendering model compared to direct rasterization.

How does ray tracing affect game performance?

So the ray tracing looks awesome, but should you go out and pre-order an RTX card now? Well, do not get too excited yet. NVIDIA claims significant improvements in the performance of regular games, especially at 4K. But when it comes to games that use ray tracing, we need to wait for detailed references. We have to play an earlier version of Shadow of the Tomb Raider and Battlefield 5 on an RTX 2080 Ti and we can not reach 60 frames per second constant at 1920 x 1080 – more than 30 to 50 frames per second. The note from Tomb Raider developers that the game should get more polished before the release, but it would not be crazy to wait for some slowness when the lightning stroke is activated. Another article appeared recently saying that Battlefield 5 with ray tracing runs on sub-30fps at 4K resolution but that Dice still has a lot of optimization to do before the game is released so we'll have to wait and see.

Conclusion: We simply do not know what kind of performance penalty ray ray will require, and at what resolutions this will make the games non-playable. It seems likely that players, at least for now, will have to choose between ray tracing at lower resolutions, ray tracing at higher resolutions and a lower frame rate, or entirely disable ray tracing.

Overall, these cards are the first generation products and are not for everyone. For starters, they are expensive, ranging from $ 500 to $ 1,000, and the list of games to support technology is relatively short at the moment. Not only that, but it does not look like there will be games that support lightning tracking when the first batch of RTX GPUs are delivered on September 20th.

But as with all the big jumps in gaming technology, these things will eventually come to more affordable cards, performance will improve and we expect more new games to support this, as there is more than one installed hardware base. For now, the RTX line is really just for the pioneers who should have the latest and the best. Players on a budget are still not enjoying the lightning stroke, but it's an exciting prospect for the future, say, in a few years time. Should you care about that now? Again, we will have to wait and see how this is implemented in the games, what is the performance penalty and if the high cost of these new cards is justified. We will all find out the answer to these questions soon.

So now you know that "Ray Tracing" is not the name of a new editor for IGN. But did you know that 8K resolution can be one thing now? Here's the skinny on how the PS5 may or may not do 8K. And be sure to check out all the details and features on the PS5.


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