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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.
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- OpenGL: Is a programming interface (API). Games send command to the video card using this language and the video driver converts these commands into instructions that de video processor can understand.Using an API games don’t need to have drivers for all video cards available at the market, as it happened in the past.
- DirectX: Another programming interface (API), see explanation above.
- Bump Mapping: Mapping technique used to create uneven surfaces like an orange skin, the asphalt on a street or a stone, for example.
- Alpha Blending: Feature used to create partial transparency between objects. This technique is used in several effects in 3D games, in objects like water, glass, etc.
- Dithering: It is possible to mix colors to obtain a color not available on the video card’s color palette. This is done in order to not require you to increase the number of simultaneous colors used by the video card, what requires more video memory. The color mixture is done putting color pixels side by side in a way that from a distance your eyes make you believe that there is just one pixel from a different color. Nowadays video cards have enough video memory to run games with 4 billion simultaneous colors (32-bit color), so this feature isn’t used by modern games – unless you reduce the number of simultaneous colors for any reason.
- Frame buffer: 3D games usually divide the video memory into two blocks, called frame buffers, in order to increase the video performance. While one image is being shown, the video card starts drawing the next image on the second video memory block.. This technique is also called double buffering. Some video cards allow the use of three video memory blocks, feature called triple frame buffer, for cases where the video card is faster than the video monitor (while the video monitor is still drawing the first image and the video card has already finished the second image, the video card can be configured to start drawing the third image in the sequence, in order to not be idle, thus improving the video performance). Depending on the context, frame buffer can be s synonym for “video memory”.
- GPU (Graphics Processing Unit) or VPU (Visual Processing Unit): Name given to the video processor when it has lightining and transform (also known as L&T) functions integrated on the chip. A long time ago these steps, that are part of a group of tasks called geometric calculation, were done by the system processor. Starting with the GeForce 256 chip these steps moved from the system processor to the video processor. Since then the 3D video performance stopped being dependent on the system’s math co-processor (FPU, Floating Point Unit) that is embbeded in the system’s processor.
- IGP (Integrated Graphics Processor): Is the name given to the motherboard’s chipset when it has embbeded video capabilities, i.e., when it has on-board video.
- Rendering: The process of creating tri-dimentional images is divided into two groups: geometric calculation and rendering. In the first step the objects to be shown on the screen are calculared. On the rendering step, they are actually drawn on the screen.
- FPS: Frames per second, the most traditional way of measuring the video card’s 3D performance. Also known as framerate, it measures the quantity of frames (full “screens”) that the video card is capable of generating per second. For a game to be “playable” the video card has to be capable of generating at least 30 frames per second on this game.The highest this value, the better. As we explained on the previuos page, descreasing the image quality leads the number of frames per second to increase. It is very important to notice that due the different gaming tecnologies available on the market the video card can obtain a very high FPS number in one game and at the same time a very low FPS number in another game. For example, a GeForce FX 5200 can obtain a good scoring on Quake III which sets this card as “playable” for this game, but this same card will reach a very low FPS score on Doom 3, making it not so good for this other game. By the way, your video card should be chosen based on the games that you will run on your PC.