boxing

Sport involving attack and defense with the fists. In the modern sport, boxers wear padded gloves and fight bouts of up to 12 three-minute rounds in a roped-off square known as the ring. In ancient Greece fighters used leather thongs on their hands and forearms, while in Rome gladiators used metal-studded leather hand coverings (cesti) and usually fought to the death. Not until implementation of the London Prize Ring rules in 1839 were kicking, gouging, butting, biting, and blows below the belt eliminated from the boxer's standard repertoire. In 1867 the Queensberry rules called for the wearing of gloves, though bare-knuckle boxing continued into the late 1880s. The last of the great bare-knuckle fighters was John L. Sullivan. From Sullivan on, the U.S. became the premier boxing venue, partly because immigrants supplied a constantly renewed pool of boxers. Boxing has been included among the Olympic Games since 1904. Today there are 17 primary weight classes in professional boxing: strawweight, to 105 lbs (48 kg); junior flyweight, to 108 lbs (49 kg); flyweight, to 112 lbs (51 kg); junior bantamweight, to 115 lbs (52 kg); bantamweight, to 118 lbs (53.5 kg); junior featherweight, to 122 lbs (55 kg); featherweight, to 126 lbs (57 kg); junior lightweight, to 130 lbs (59 kg); lightweight, to 135 lbs (61 kg); junior welterweight, 140 lbs (63.5 kg); welterweight, to 147 lbs (67 kg); junior middleweight, 154 lbs (70 kg); middleweight, to 160 lbs (72.5 kg); super middleweight, 168 lbs (76 kg); light heavyweight, to 175 lbs (79 kg); cruiserweight, 190 lbs (86 kg); and heavyweight, over 190 lbs. A bout can be won either by knocking out or felling one's opponent for a count of 10 (a KO) or by delivering the most solid blows and thus amassing the most points. The referee can also stop the fight when one boxer is being badly beaten (a technical knockout, or TKO) or he can disqualify a fighter for rules violations and award the fight to his opponent.

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Freshwater tropical fish (Betta splendens; family Belontiidae or Anabantidae), noted for the males' pugnacity toward one another. A native of Thailand, it was domesticated there for use in contests. Combat consists mainly of fin nipping and is accompanied by a display of extended gill covers, spread fins, and intensified colouring. This slender fish grows to about 2.5 in. (6.5 cm) long. In the wild it is predominantly greenish or brown, with red fins; domesticated, it has been bred with long, flowing fins and in a variety of colours, such as red, green, blue, and lavender.

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Z-fighting is a phenomenon in 3D rendering that occurs when two or more primitives have similar values in the z-buffer, and is particularly prevalent with coplanar polygons. The effect causes pseudo-random pixels to be rendered with the color of one polygon or another in a non-deterministic manner, varying as the scene is animated, causing one polygon to "win" the z test, then another, and so on. The overall effect is a flickering noisy rasterization of two polygons which "fight" to color the screen pixels. This problem is usually caused by limited sub-pixel precision and floating point & fixed point round-off errors.

Z-fighting can be reduced through the use of a higher resolution depth buffer, by w-buffering in some scenarios, or by simply moving the polygons further apart. Z-fighting which cannot be entirely eliminated in this manner is often resolved by the use of a stencil buffer, or by applying a post transformation screen space z-buffer offset to one polygon which does not affect the projected shape on screen, but does affect the z-buffer value to eliminate the overlap during pixel interpolation and comparison. Where z-fighting is caused by different transformation paths in hardware for the same geometry (for example in a multi-pass rendering scheme) it can sometimes be resolved by requesting that the hardware uses invariant vertex transformation.

The more z-buffer precision one uses the less likely it is that z-fighting will be encountered but it is inevitable that coplanar polygons will exhibit this problem unless corrective action is taken.

As the distance between near and far clip planes increases and in particular the near plane is selected near the eye, the greater the likelihood exists that you will encounter z-fighting between primitives. With large virtual environments inevitably there is an inherent conflict between the need to resolve visibility in the distance and in the foreground, so for example in a space flight simulator if you draw a distant galaxy to scale, you will not have the precision to resolve visibility on any cockpit geometry in the foreground (although even a numerical representation would present problems prior to zbuffered rendering). To mitigate these problems, zbuffer precision is weighted towards the near clip plane, but this is not the case with all visibility schemes and it is insufficient to eliminate all z-fighting issues.