Temporal Anti-Aliasing (TAA)

The main concept of temporal anti-aliasing is to use a subpixel jitter of scene camera every frame and then combine all this frames into the final image. So, it will take time to get a smoothed picture (for example, 5-7 frames), but with the frequency of 60 frames per second it will look seamlessly.

During rasterization process, there is a test whether the object will get into pixel or not. And the object will not be rendered if it doesn't occupy a major part of a pixel.

And here we can get an error, when we have a sphere object before rasterization and get a square object after, because some parts of the sphere doesn't occupy enough pixel space.

Not a very good rendering, right? And temporal anti-aliasing solves this problem, because camera will have a subpixel jitter, and each part of this sphere at least once will be rendered in a frame. And after combining these frames, we will get a true sphere, not a square! Voila!

This anti-aliasing technique works perfectly for static scenes (without any moving objects). But when objects are moving, frames will significantly differ one from another and we will see a trail of "ghosts" of the moving object. This effect is called ghosting.

To get rid of ghosting, there is a velocity buffer. Velocity buffer stores information about transformations of objects. Due to this buffer, the engine knows about the object transformation and don't render the "ghosts" of the moving object. Also, the engine checks the color intensity of the pixel, because of camera jitter.

TAA has a wide scope of usage, because it improves whole image (not only the edges of the geometry, like MSAA) including geometry, shadows, etc. It greatly reduces all the problems, and does not cut the performance down, working well with both static and dynamic images. However, keep in mind that the key factor of good TAA performance is optimized content of the scene: the higher FPS is, the faster temporal anti-aliasing smooths the scene. In addition to this, UNIGINE allows you to choose the type of anti-aliasing: TAA or FXAA, or combine them both for better image quality (FXAA is applied before temporal summing).

The following settings are available when the Custom preset is selected.

Below is an example of TAA settings for relatively static scenes.

• The Diagonal Neighbors option should be enabled, as it provides more accurate pixel color information reducing the stair-step effect. At the same time TAA causes more blurring is case of fast camera movement, which is especially noticeable on grass and other similar high-contrast screen areas.
• Preserve Detail value is decreased to reduce flickering of small pixels.
• The number of TAA Samples is set to 16, which increases the number of variants for subpixel camera jittering, thus making the stair-step effect even less noticeable.

Below is an example of TAA settings for very dynamic scenes where trails from thin objects are especially noticeable.

• The Diagonal Neighbors option should be turned off, as it may result in significant blurring of small details in motion.
• Increase the Preserve Details value up to 1 or higher to reduce ghosting effect for moving objects.
• Set TAA Samples value to 4 to reduce flickering of small pixels when the camera does not move.
• It is also recommended to reduce Max Frame Count to 60 or lower, to accumulate less frames for slow motion, reducing the ghosting effect.