Anti-Aliasing: know the effect responsible for improving your gameplay

you know that serrated strange that sometimes it bothers, seen in the image of some games? This is called AliasingAnd Anti-Aliasing it is there precisely to be able to rid your gambling of this evil. Everything your computer or cell phone shows, whether images, videos, is actually a junction of color dots. These points are called pixels. The pixel is nothing more than just the smallest element of a device, a point that will form an entire image.

Many current graphics cards on the market have focused a lot on improving the gamers experience, improving the rendering and improving the serrated when playing. THE NVIDIA incorporated some of these effects into the new GTX, already the AMD did the same thing with the line Radeon.

Even if companies like NVIDIA manage to develop new technologies like Ray tracing, method that makes a better calculation of rendering compared to others used, still the aliasing will be a problem.

What is Aliasing and why it causes such a strangeness

To better understand how the methods work Anti-Aliasing, and even the Aliasing In itself, it is necessary to understand how screen resolution works and how they form the images we have on devices today. That serrated it is caused precisely because screens render pixels.

The devices screen works as if it were a grid. Each rendered pixel is the result of a calculation of all the spatial information usually calculated by the graphics card to render the information on the screen.

In practice, this means that slanted or curved lines will not be of exact quality unless the grid has many divisions. This kind of serrated and lack of information on the screen, generates the effect Aliasing. The problem is that the more divisions, the more it reduces the effect aliasing, more expensive for the graphics card to process this information.

Not only the resolution, but all the hardware is directly responsible for processing the information. They are shadows, reflections, they are expensive internal calculations to process. And all the advancement of the new Engines makes the computer need more calculations to process.

Usually surface and materials calculations Physically Based Rendering (PBR) depend on several components besides texture. Components like normal map, emission map and reflection map only add up the GPU and Graphics Card process when calculating. Now imagine calculating a resolution 1080p (1920 1080 ×).

Of course, nowadays, this process is much less expensive than thinking about 5 or 10 years ago. But still many calculations can leave their marks on pixels or may not be calculated correctly, taking into account that some games have pipelines different rendering. Even with the high technology and several calculations being done faster, pixels can still be disconnected and generating the effect Aliasing for players.

One of the pipeline of rendering widely used by current engines is the painter's algorithm, which renders the background first, and then renders the objects closest to the camera, similar to the technique used by painters. This type of calculation is done by Engine, and gamers don't usually worry about this when playing a game, unless it's their own developer. engine.

Often when playing you can see that usually the farthest parts are rendered first, and then the computer worries about rendering the parts closest to the camera. For this, there are several methods correction, called Anti-Aliasing, applied directly to the pixels on the screen, as well as methods that soften the aliasing. methods that are applied directly to the game development, such as the MipMapping and Level of Detail (LOD or Level of Detail).

Anti-Aliasing Solutions

Realizing that, with all this processing and, with technological innovations, this problem will be constant in the game development. As if it weren't enough for developers to have to worry about all the programming, interactions, interface, and all the art, animations, the visuals. serrated becomes another problem to be fixed in the industry.

For that, several solutions were created, some very expensive and others absolutely viable and applied in several games.

OASA: Outer Edge Anti-Aliasing

This solution is basically specific to cases like Dead Space, where the model lines intersect with other models or the background. Some graphics cards such as AMD do this calculation already.

It works as a programmable custom filter mode that applies an algorithm to the frame buffer to calculate which pixels can be blended to generate smoother gradients. It also has the possibility to collect extra samples outside the pixel boundary.

MSAA: Multi Sampling Anti-Aliasing

This algorithm Anti-Aliasing identifies several mediated locations between pixels that are not perceived by human eyes, based on the resolution of the monitors. And it couples that with the final shader rendering, which is basically how the object looks in the scene.

This process is only seen better at low resolutions like 720p and the cost is still high because it needs to be calculated for every pixel at every frame. Increasing the number of frames, the cost gets even higher.

This technique is only applied to the edges of objects and transition zones of the three-dimensional object.

FXAA: Fast Approximate Anti-Aliasing

The algorithm Anti-Aliasing created for NVIDIA to cover the shortcomings of MSAA. It costs the computer less processing. The main difference from MSAA is that FXAA only fetches the edges of the object instead of all frames.

The main loss of this technique is linked to the movement, since the pixels can lose definition, causing a blur in the image. The way to solve this is to add another effect, called motion blur, which will blur every time it detects motion.

SMAA: Sub-pixel Morphological Anti-Aliasing

This technique is becoming the most popular among modern game developers. The method analyzes the current and previous frame and creates a blend of the pixels, forming a sub-pixel. With this, it can generate a sharper image.

While it is an improvement over FXAA in terms of blur and sharpness, the effect can still have issues when the subject is moving.

TXAA: Temporal Anti-Aliasing

As the name suggests, this effect Anti-Aliasing aims to reduce the blur problem with objects moving at high speeds, more specifically what the frame-rate is capable of rendering.

When the object's speed is higher than the device's frame-rate, it causes some frames to be dropped, giving the sensation that this object appears to be jumping in the scene, when it is not.

TXAA will then solve this problem by interpolating the dropped frames on the screen, giving the feeling of continuity and not losing information. Although this effect is kind of invisible to the human eye, the fact that some frames are missing is noticeable.

SSAA: Anti-Aliasing Supersampling

This method of Anti-Aliasing uses a higher resolution render to produce a lower resolution image with less artifacts and aliasing. Through this method, the diagonal line is transformed into a digital image with a higher resolution, allowing more detail to be reproduced than before. This causes it to convert to a higher fidelity image when the resolution is reduced to what the screen or monitor will use.

ATAA: Adaptive Temporal Anti-Aliasing

To perform Anti-Aliasing on rendering technologies Ray tracing, one must take into account the basic principle of the technology. O Ray tracing traces rays, starting from each pixel of the screen in relation to the camera, that go towards the objects of the scene.

The central idea is to run the algorithm ATAA on most pixels and produce a large amount of information that will contain information on the pixels that failed and the reasons for failing. After this information is completed, the algorithm will replace with ATAA's complex heuristics on the faulty pixels. The algorithm aims to better adapt to the image content.

The problem goes beyond that

even if effects Anti-Aliasing are combined for the best solutions and strategies in the game, this still doesn't stop other problems from occurring. Many of the aforementioned methods basically resolve motion and object edges. Sometimes even gentle movements can cause the aliasing of textures or even the computer can process oversized models from a distance.

This generates several problems, because textures and models in high resolution, even if a piece of the screen appears, it is necessary that the entire object is processed. The problems associated with this type of practice are again related to costs.

MipMapping – The texture solution

In computer graphics, mipmaps are sequences of pre-computed images, each being a smaller scale representation of the same image. They are grouped into a texture atlas and used based on how far the object is from the camera.

Rendering the texture at its actual size too far from the camera, in addition to being expensive, does not bring a visually pleasing result to the eyes. The solution comes so that, over long distances, the texture has the same fluidity as seen by the human eye.

LOD: Level of Detail – The solution in 3D models

LOD has the same principles as MipMapping, only applied to models 3D. Models with many vertices being rendered too far away from the camera take a lot of processing and are not visually pleasing.

This method comes to reduce the geometry and complexity of this model so that it still doesn't lose its properties in the scene. This method is often merged with Mipmapping so that both the model and texture are reduced in size for the given distances.

What type of Anti-Aliasing is best for you?

Many video cards use the effects Anti-Aliasing shown above, and many of them are available to be enabled or disabled by the settings. It is up to the user to choose which one to use, based on which machine he uses.

Apart from the OEAA, which is not a post-processing effect, all the others are post-processing effects, which will be applied to every frame. This, of course, will impact which machine will be used.

Gaming computers and notebooks focused on graphics cards and good RAM and GPU processing will process Anti-Aliasing that demand more from the machine. Despite the many variations cited, it is worth setting up a short list of which effects to use for the machine level the user has:

• FXAA: Popular and not so expensive;
• MSAA: Low cost, but not so used lately;
• TXAA for mid to more robust PCs;
• SSAA: it is absolutely expensive, but with high quality;
• ATAA: is a new technology for new GTX cards.

Of course, this classification is more basic, and it will depend, for example, on which video card users have. NVidia, for example, has a wide portfolio of cards that do a good TXAA calculation compared to other graphics cards. Some AMDs process FXAA well in addition to SMAA for better gain. Weaker PCs, due to their hardware limitations, tend to be more constrained in choices.