Along with the penis, the scrotum is sensitive and considered to be an erogenous zone. High heel pornography involves women or men dressed in high heeled shoes. Foot fetishism, foot partialism, foot worship, or podophilia is a pronounced sexual interest in feet. Initially, few animation studios in the United States attempted to produce animation for adult audiences, but later examples of animation gay boy porn produced for adults would gain mainstream attention and success. An orgy is a gathering where guests freely engage in open and unrestrained sexual activity or group sex; and a bunga bunga orgy is an orgy in which participants have sex underwater, such as in a swimming pool or a hot tub. Mutual masturbation is a sexual act where two or more people stimulate themselves or one another sexually, usually with the hands. Pornographic films or sex films are films that present sexually explicit subject matter for the purpose of sexual arousal and erotic satisfaction of the viewer. The fundamental principles for the exercise of BDSM require that it should be performed with the informed consent of all involved parties. Com, there are only 655 bisexual titles out of a catalogue of more than 90,000 films. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. As in B/D, the declaration of the Top/Bottom may be naked milf required, though sadomasochists may also play without any Power Exchange at all, with both partners equally in control of the play. Some restrict a policy of panties/nipple tape for females and some allow full nudity with explicit sexual interaction allowed. These scenes may either have the cameraman directly engaging in sex or merely filming others having sex. Such films continued to be produced but could only be distributed by underground channels. Some couples use pornography at times for variety and 3d hentai to create a sexual interest or as part of foreplay.