Is also common of the furry genre. Reality and voyeur pornography, animated videos, and legally prohibited acts also influence the classification of pornography. Most bisexual porn is made by small production companies rather than the major studios. Group sex pornography features at least two men and two women , usually more, who all perform sex acts on each other. They may regard it as an enhancing element of their sex lives or as their primary form of sexual activity. Bestiality is illegal porn milf in many countries. Pornography may be presented in a variety of media, including books, magazines, postcards, photographs, sculpture, drawing, painting, animation, sound recording, film, video, and video games. The full-weight body-pressure, moisture, sex odors and darkness can be perceived as powerful sexual attractions or compulsions. Patricia Hill Collins, an African-American writer, theorizes that this is derived from a stereotype that those of black descent are promiscuous, and their buttocks are objectified by porn as a result. The hentai movies Silent Duck, also called Duck-Billing, is the technique often used in which the person engaging in hand insertion shapes the hand to resemble a duck beak. Usually that person prefers to stage the wetting so that his/her legs become soaked with urine. Use of the agreed safeword is seen by some as gay twinks an explicit withdrawal of consent. Additionally, the buttocks give an indication of the shape and size of the pelvis, which impacts reproductive capability. The object or situation of interest is called the fetish; the person who has a fetish for that object/situation is a fetishist. Because the viewing of such films carried a social stigma, they were viewed at brothels, adult movie theaters, stag parties, at home, in private clubs and also at night cinemas. Both sexes sometimes apply lubricating substances to intensify sensation. Bondage pornography specializes in the depiction of sexual bondage or BDSM activities as photographs, stories, movies, or drawings.