Common positions include lying on back or face down, sitting, squatting, kneeling or standing. This can, however, redirect semen into the bladder . Sexual relations between women have been illustrated as well as narrated, but much of the written material from the early modern period has been destroyed. Real medical shots or videos may violate privacy laws in some countries. Incest itself is largely taboo, and is a crime in many countries. Bukkake pornography involves a performer, usually female, onto whom several men or women ejaculate, usually on the face. Tentacle erotica can be consensual, but gay twinks frequently contains 3d hentai elements of non-consensual sex. For legal reasons, the vast majority of so-called reality porn involves professional actors and actresses posing as so-called amateurs. Threesome can also refer to a love triangle, a three-way romantic relationship. Irrespective of the legal or social view of pornography, it has been used in a number of contexts. Usually that person prefers to stage the wetting so that his/her legs become soaked with urine. Diaper pornography involves performers wearing diapers, sometimes with an naked milf adult performer acting in the role of a caretaker. Dwarfs or midget pornography features performers who are dwarfs/midgets. When the interest in a particular subject is obsessive, the behavior may be described as stalking. For example, in Australia it is rated Refused Classification . Double penetration of the vagina, anus and mouth, can involve: Simultaneous penetration of the anus by two penises or other objects. Is also common of the furry genre. It is typically animated pornography, as the legal age to be featured in a pornographic film in Japan is 18. Other objects such as ball point pens and cartoon porn comics thermometers are sometimes used, although this practice can lead to injury and/or infection. Clothes wetting: The person is sexually aroused by wetting one clothing or observing another person doing so. A survey by the New York City Department of Health and Mental Hygiene found that heterosexual women are more likely to bareback when engaging in anal sex than homosexual and bisexual men.