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If my male figues are depicted in a sexually aroused state, that would condemn my 3D renders as pornographic ?  Even if done with tasteful setting, decor and lighting  ? 

And if they were shown in non-aroused state, same environments, it would be erotica ?  Or, considered just nude art like the grand masters of the Western tradition 1500s-1800s ?

male nudity in a movie might give it an R rating. a male erection in a movie will give it a XXX one instantly.
a nudist colony or beach generally has hundreds of nude people - men women and children. it is an environment thought of as natural and non-sexual by most people there. they dont go there to get their rocks off, but rather to relax and become comfortable in their own skin. see how long you last walking around one with an erection. they have strict policies against photography, overt public affection/sexuality, hitting on people, bringing in pornography, sexually explicit language, even suggestive jewelry.

these days in most cultures nudity in itself is not pornography. suggestive nudity can cross the line into erotic art. i define pornography as involving sexual acts. pornography can be artistic, but this is generally an afterthought and not the primary purpose.
things change with the times. these days i wouldnt even call Playboy pornography -- but rather a mens magazine with some nudes.