The only objectional non subjective way I can think of is lubricity--trying not to gross anyone out-- in the nether regions. Fear, surprise and pain all look as much like arousal as bliss in the face. I don't know about anybody else's nipples but mine have a mind of their own and it has more to do with temperature and rough material than arousal whatever they do. If we are not doing insert shots, then the only way to tell in a Pose render-- beyond paranoia-- is damp upper thighs. Anything else is wishful thinking. Emily