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Glossary Of Basic Graphics Terms

Graphics Beginners' Guide, Part 2: Graphics Technology
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Refresh Rate

Just like movies or television, your computer simulates motion on your monitor by displaying a series of different images. Your monitor's refresh rate is the amount of times that the graphics card will update this image every second. A refresh rate of 75 Hz means that the monitor image is refreshing 75 times per second.

Refresh rate problems may arise in a video game when the computer is processing frames faster than the monitor's refresh rate. For example, if the computer is fast enough to process 100 frames per second, and the monitor's refresh rate is 75 Hz, there will be times when a frame is calculated and is displayed halfway through one of the monitor's refreshes. This can cause "tearing" or "artifacts," which is a nuisance.

As a solution, V-sync (short for vertical synchronization) can be enabled. This limits the frames the computer processes to the exact refresh rate of the monitor, and prevents artifacts. For example, with V-sync enabled the calculated frames in a game will never exceed the refresh rate. A 75-Hz refresh rate would limit the computer from calculating more than 75 frames per second.

Pixel

Pixel stands for "picture element." It is simply a small dot of graphical information on your display - the representation of a color (for most purposes these are values of red, green and blue). If your screen resolution is 1024x768, your screen shows a grid of 1024 pixels wide by 768 pixels high. You see the image on your screen when all the pixels are shown together. The displayed content updates between 60 and 120 times per second depending on your display type and the amount of data generated by the graphics card and output. CRT monitors draw the complete display line by line while flat panel displays can update each pixel individually.

Vertex

All objects in a 3D scene are made up of vertices. A vertex is a point in 3D space with X, Y, Z coordinates. Multiple vertices joined together (at least three of them) build a polygon that can be as simple as a triangle, a cube or a more complex shape. A texture is then applied to it to make this element (or a number of aligned elements) look real. The 3D cube pictured above is made up of eight vertices. More complex objects may appear to have curved shapes, which you can achieve by using very large amounts of vertices.

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