Partners can engage in penetrative sex, known as full swap, or choose to soft swap in which they engage only in non-penetrative sex. Going back at least as far as the Christy twins in the 1970s, depictions of incest and particularly incest between twins has been a feature of gay pornography. For example, the Kama Sutra, in particular, goes into specific detail on how to properly strike a partner during sex. Such films continued to be produced but could only be distributed by underground channels. There is also some evidence that pornography can be used to treat voyeurism. Interracial pornography typically employs ethnic and gay fuck racial stereotypes in its depiction of performers and many of interracial pornographic films still include racial stereotypes, although the segregation of actors by race has diminished considerably. They cited the Internet and text messaging as common ways of organising meetings. Amateur porn has been called one of the most profitable and long-lasting genres of pornography. Others may also use vibrators and other sexual devices more commonly associated hentai videos with female masturbation. A common way that these are depicted in a single scene is momporn with one woman and two men performing together. The sub-genres usually conform to certain conventions, and each may appeal to a particular audience. Jail/Prison/Police pornography involves people in police custody or inmates in jails or prisons in various sexual situations, such as strip searches or body cavity searches. Sadomasochism does not imply enjoyment through causing or receiving pain in other situations . Individuals who can change between top/dominant and bottom/submissive roles—whether from relationship to relationship or within a given relationship—are known as switches, though the term switch in this context is occasionally seen as derogatory and is rejected by many who might simplistically fit the definition. Homi Bhabha defined the idea of a racial fetish in contrast to the idea of the Freudian sexual fetish which he describes a denial of difference, where the male sees the female as a castrated male, seeing missing parts rather than a different anatomy.