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What is Antialiasing?

Your first thought when you hear the word “antialiasing” may be that it’s something law enforcement should be looking into. But that’s hardly what the term is all about. But what is antialiasing really?

Even when sophisticated computer games arrived on the scene, images were very basic by today’s standards. Computer monitors had nowhere near the resolution and intensity that we now enjoy, and processors were not capable of the motion and image processing high-powered games now require.

In computer graphics, displaying an image on a device that does not have resolution properties high enough to present smooth curves for objects can result in lines that appear step-like or jagged. This phenomenon is known as aliasing.

Antialiasing (also sometimes referred to as dithering or oversampling) is a set of techniques that reduce these effects to provide a higher-quality image. It has been enhancing 3D gaming presentation quality for over a decade.

It has made many improvements over the years, providing continuously higher quality and realistic images.

Where Does Antialiasing Apply?

If you’ve played many of today’s sophisticated video games, you may have noticed options that allow you to select antialiasing options, or perhaps your video card configuration includes options for selecting from multiple antialiasing options.

These options can be an important decision, as the various techniques demand significantly different levels of resources from your system or graphics controller.

When you’re selecting a graphics card for your system or setting up options in a new game, you need to understand the benefits (or consequences) of your decisions. Some graphics cards will not provide options but may offer multiple drivers.  These can be installed to utilize varying antialiasing approaches.

Like gaming systems themselves, graphics and monitor resolution have improved incredibly in recent years, such that aliasing is not the factor that it was in the past.

Still, given the opportunity to select antialiasing options, you should be aware of the benefits and implications of your choices.

What is Antialiasing: 9 Types of Antialiasing Techniques

To further learn what is antialiasing, we’ll list down the types of solution to aliasing. There are some approaches to solving the aliasing issue, each of which will provide smoother lines for your gaming or other graphic displays. There are two major ways to solve the impact of aliasing on computer graphic images:

  • Increase the sampling rate to provide a higher level of detail in the output generated.
  • Blur the edges of geometric shapes to make the effect less visible.

FSAA

Full-Scene Antialiasing is one of the most basic and oldest types of antialiasing, sampling input pixels and analyzing the colors of surrounding pixels to generate an average. This average will be the color of the resulting output pixel. The problem with FSAA is that the method does not result in a precise correction for the output that you see on your screen.

MSAA

Multi-sample antialiasing is probably the most predominant type in use today. When your computer recognizes a geometric shape in your game, it samples the colors around the edges and fills any jagged edges with the average of the colors present. So the edges appear nice and smooth, and the human eye can’t distinguish that the blend has even been performed.

But this smoothing comes at a cost. You may be provided with the option of selecting the number of samples to be taken (typically 2, 4, 8, or 16). Some high-powered graphics processors today even expand the sampling options up to 128. The higher the sampling level, the more processing your graphics card has to do, which could impact your performance.

While MSAA does a good job of smoothing edges and lines, it is not quite as effective when it comes to color detail or smoothing textures.

Adaptive Antialiasing

Adaptive Antialiasing works well with transparent/alpha textures without the overhead in processor requirements that SSAA consumes. AA is an extension of MSAA.

FXAA

Fast Approximate Antialiasing – takes a different approach to the problem. Rather than calculating based on object geometry and performing analysis on each frame, FXAA applies to smooth to entire images without regard for individual objects. This reduces the load on your graphics processor, but image clarity suffers, producing a slightly blurrier image.

MLAA/TXAA

Morphological Antialiasing and Temporal antialiasing (used by AMD and Nvidia respectively) are the same processes.

Similar to MSAA, these methods perform sampling to smooth graphics presentation. But instead of calculating using the current frame, it utilizes data from the previous frame for color sampling. This improves efficiency over MSAA.

MLAA can still result in some level of blurred texture in the resulting image but still improves over prior types of antialiasing.

CSAA

Coverage sampling antialiasing was developed by Nvidia and provides image results very similar to MSAA, although with a slightly higher impact on system performance.

CSAA appears similar to MSAA but achieves acceptable performance through sampling fewer colors in each analyzed area. Performance is improved, but the resulting image may be less accurate, or video quality may suffer slightly.

EQAA

Enhanced Quality Antialiasing was developed specifically for the Radeon graphics cards manufactured by AMD. This solution provides higher quality over MSAA, and results similar to CSAA, with a minor performance impact.

SSAA

Supersampling antialiasing escalates your graphic results to the highest level. This is done by transforming your game image into a higher resolution, then sampling it down – essentially shrinking the image – to fit the true resolution of your display. This provides you with the illusion of having a higher resolution screen, for a clearer image.

The problem with SSAA is that it consumes considerable resources to perform its sampling and transformation. This can have a dramatic impact on the performance of your system, especially on a medium-range computer system.

SMAA

Subpixel Morphological Antialiasing uses the same basic technique as MLAA but provides improved processing performance through its efficient use of modern graphics processors. SMAA also improves on blurring issues for better overall antialiasing results.

When given the choice of antialiasing techniques, why not try them all? Then you can see for yourself which option provides you with the best overall image quality, without a major impact on performance.

How Does Sampling Work?

Now that we know what is antialiasing, we well look at Sampling. When performing the sampling necessary for antialiasing, there are multiple methods that can be utilized:

Point Sampling

Point sampling utilizes a single sample of the input image area to generate the resulting output pixel, without respect to the surrounding area. This can result in data that is lost due to a large portion of the input image not being represented in the sampling. The resulting image could suffer significantly in quality and translation.

Area Sampling

Area sampling produces a far superior image as compared to point sampling. This is because it defeats the intrinsic flaw of point sampling by sampling an area of the input image (rather than a point) and filtering the content to map the resulting output pixel.

Supersampling

With supersampling, multiple samples are taken per pixel, with an average taken for creation of the output pixel.

For example, if the resolution of your display only supports one third as many pixels as your input image, nine input samples will be averaged into three for the output image. So if nine samples are taken with three being blue and six being green, the resulting output will be one-third blue and two-thirds green.

What are Your Options?

To answer that question – it depends.

Some games may not even provide you with options for setting your antialiasing functions. Others will include a vast array of graphics and sound options available.

Your graphics card manufacturer may also provide you with configurable antialiasing options, or drivers you can download and install to expand the available list of settings.

You should experiment with the mix of options available to you until you find what works best for your applications and hardware. Even within a particular type of antialiasing, you can tweak the settings for sampling to get the best image results without dragging down your performance.

Start with the best type and sampling rates that you can select. Then work down from there until you’re satisfied with the quality and performance.

Determining the Best Antialiasing for You

It’s worthwhile to spend a little time to determine what is antialiasing and what type works best for you.

Depending on the games you play or graphics resolution you need for other applications, take full advantage of the antialiasing method that provides the best mix of quality and performance.

Even with the highest resolution monitors, antialiasing will improve the overall appearance of your images.

If your system has the power that makes performance a non-issue, use the highest type of antialiasing your computer and graphics card can support.

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