Voyeur pornography may also include shots of topless women on topless beaches who are unaware of the cameras but may legally mature milfs be photographed due to the public setting. In the 18th and 19th centuries, some European theologians and hentai movies physicians described it as heinous, deplorable, and hideous, but during the 20th century, these taboos generally declined. Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates, and not necessarily on the market to which each sub-genre appeals. Rape pornography features performers simulating rape. Perhaps following the example set by gay pornography, they have become a popular subgenre within heterosexual pornography since the turn of the century, featuring both vaginal and anal ejaculations. In POV porn, the shooting style is generally similar to gonzo pornography, with the person receiving sexual gratification holding the camera him or herself—aiming it down at the actress or actor who is performing the sex act. Bondage websites and bondage imagery in mainstream pornography As of 2003, specialist bondage magazines were mostly displaced by the availability of bondage material on the World Wide Web, and the presence of bondage imagery in mainstream pornographic magazines such as Nugget and Hustler Taboo magazine. Yaoi is anime or manga that features gay males . Preggo pornography features pregnant performers and may include erotic lactation as a fetish. Diaper fetishism, nappy fetishism or diaperism, is a sexual fetish in which a person feels a desire to wear or use diapers. As a form of non-penetrative sex, it can be done for its own enjoyment or as foreplay. It is also known colloquially as gushing or squirting, although gay cock these are considered to be different phenomena in some research publications. Mammary intercourse is a sex act, performed as foreplay or as non-penetrative sex, that involves the stimulation of the male penis by the female breasts and vice versa.