[Hardware] Why does AMD have worse performance in Ray Tracing?

[FNX Magokiler]

One of the things that is talked about at length is the poor performance of AMD graphics cards in Ray Tracing, especially compared to NVIDIA's. However, many throw their hands up when we say that the implementation of the necessary hardware by the Radeon Technology Group is so poor that it seems literally like a boycott of the adoption of this technology. Which we remember that it is ideal to solve certain visual problems in computer graphics and it is not an invention of the manufacturer of the GeForce.

For us, the main function of a graphics card is that it allows us to play our games with ease and performance, at the same time that if you are going to need it for more professional tasks, such as video editing or the creation of 3D models, it is more than enough. with his work. When we say that AMD has little performance in Ray Tracing, we are not putting NVIDIA through the roof, but rather, as users that we are also, we are saddened to see that something that in Radeons could be much better, is not.

The ray tracing algorithm
To understand the poor performance of AMD cards in Ray Tracing we have to understand that this is actually a recursive algorithm to generate a complete scene, which in its simplest version can be summarized as follows:

For each pixel in the scene
Calculate the visualization ray
If the lightning strikes an object, evaluate the color of the object.

 

If not, that pixel has the background color.
The ray is nothing more than a vector that moves from the camera that "records" the scene and that crosses a matrix of points or a mesh, where each one of them is a pixel. Each time a check effect will be performed on the scene. Well, if we have a scene in Full HD this means that 2 million checks will have to be carried out, if the game is at 60 FPS this is 120 million checks per second.

Mathematically, the most common formula to check it is not a simple operation, but rather a complex equation with vectors, which requires some power. So much so that the simple fact of not having a parallel unit in charge of carrying out this task can reduce the percentage performance to single digit figures.

Hardware intersection units
That is why NVIDIA has the RT Cores and AMD has the Ray Accelerator Units, they are the same, since they are the same type of unit and are used for the same task. However, in the last generation, the RX 6000 had a limitation that luckily the RTG has solved in RDNA 3 and, consequently, in the RX 7000 range.

 

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