Alternatively, the motion of the breasts may be governed by custom-written software, but this is more time-consuming and therefore rarer than using springs, which are a built-in feature in many game engines. The setup and strength of these springs determines the strength of the breast bounce. To effect breast movement in most 3D games, the breast's bones are equipped with 'springs' that make the breasts bounce when the rest of the skeleton moves. To make breasts or other body parts move, video game animators make the bones' joints move according to the physical rules of the game's engine. These virtual bones do not necessarily correspond to the bones in real humans, but are required to make anything move.

In a game with 3D graphics, character models are composed of a skeleton of 'bones' connected with joints and covered by a 'skin' of textured polygons.

Technology īreast physics is an application of soft-body dynamics, the field of computer graphics that focuses on physical simulations of the motion and properties of deformable objects. The purpose of the initiative was to create games that deal 'with an aspect of female breasts other than the fact that they're sexy and fun to look at'. In reaction to the prevalence of big, bouncy breasts in video games, games writer Jenn Frank initiated a 'boob jam' in 2013. The game's publisher Capcom attributed it to a bug and later removed it by a patch. Although this behavior was noticed by media even before the game's release, it remained present in the released version of the game. On occasion, this aspect of fighting games has caused particular attention, such as when the 2015 game Street Fighter V had the fighter Chun-Li's breasts move like large water balloons when she was chosen as the second player's character in the selection screen. The Dead or Alive series (1996–), in particular, has become identified with the 'outlandish' physics of both its fighting moves and its female characters' breasts its developer Team Ninja created the term 'breast physics'. Pronounced breast physics have since remained a staple feature of many fighting games, perhaps in part because these games contain fewer character models than other games and can therefore afford to animate their characters in more detail. The first video game in which breast physics were a notable feature was the fighting game Fatal Fury 2 (1992), which featured the fighter Mai Shiranui, who had noticeably jiggly breasts.

A fan dressed as Mai Shiranui, a popular fighting game character who is a notable early demonstration of breast physics technology

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