If you open the configuration menu of your favorite 3D game you will find several image quality configuration options. When we descrease the game image quality we increase the gaming performance. This occurs because there will be less things to be drawn on the screen, thus the graphics chip will have less to do. If you have a less powerfull VGA you can increase its performance by descreasing its image quality.
For newbies, however, the image quality configuration options look like Greek. In this tutorial we will explain the most common image quality related terms found in 3D games.
- Anti-alising: This technique is used to smooth the “tooth saw” aspect of diagonally drawn lines. In 3D games this option can be usually configured at none or disabled, 2x, 4x or 6x (or low, med and high, in some games). The higher the value, the better the image quality, but slower the game will be. Also known as FSAA (Full Screen Anti-Aliasing).
- Bilinear Filtering (interpolation): This filtering technique makes color transitions smoother. For example, if there is a transition between an yellow area to a red area the bilinear filtering will make the junction region of these two areas smoother (will create a color change from yellow to red).
- Trilinear filtering: This filtering presents a smoother transition between colors than bilinear filtering, but makes the game slower.
- Anisotropic filtering: This kind of filtering enhances the quality for images that are not on the conventional plan. To better illustrate this feature, remember Star Wars opening titles. As the letters go to the top of the screen, they become fuzzy and hard to read. Anisotropic filtering is used to get a sharper image and to not become fuzzy like in this example. This filtering can be usually configured as the number of samples used on the filtering process (2x, 4x, 8x, 16x). The highest the number of samples, the sharper the game image will be, but the game will be also slower.
- MIP Mapping: A filtering method where the original texture is applied again over the object several times using smaller sizes. When the object is distant what sometimes happens is that the texture to be applied is larger than the object itself and the VGA has to “squeeze” the texture to make it fit on the object, creating an annoying visual effect called Moiré noise. With the MIP mapping enabled, a smaller texture – one that fits the object without the need of being “squeezed” – is applied, thus solving the problem. MIP mapping is actually an anti-aliasing technique.
- Z-buffering: Traditionally the video memory stores only the color information for each pixel on the screen. With z-buffering technique implemented, the video memory is also used to store information about the z axis (depth) of the image, thus increasing the rendering speed, since the VGA will know that objects hidden behind another objects don’t need to be drawn. When z-buffering isn’t used, a lot of calculations is needed to set the spacial position of each object on the screen and to know if one object is in front or behind another one.