Z-buffer The z-buffer is a reserved portion of video memory that holds depth information (as opposed to color information) for every pixel being displayed on the screen. When a polygon is rendered with z buffering, each of its pixels’ depth (z-value) is compared with the corresponding value stored in the z-buffer. If the value stored in the z-buffer is less than the depth of the new arriving pixel, it is decided that this pixel is visible and should therefore be rendered. The z-buffer is then updated with the pixel’s depth. If however, the value is greater, the pixel is rejected and will not be rendered, as this means it is behind of what has already been drawn. Z-buffering is used to ensure that objects are rendered in the right order, that is, objects in the back should not appear in front of objects that are in the front.Zig-zag scanning order A specific sequential ordering of DCT coefficients from (approximately) the lowest spatial frequency to the highest. ZV Port Short for Zoomed Video Port, a port that enables data to be transferred directly from a PC Card to a VGA controller. The port is actually a connection to a zoomed video bus. This new bus was designed by the PCMCIA to enable notebook computers to connect to real-time multimedia devices such as video cameras. The first notebook computers with the ZD port arrived in late 1996.
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