Rim lights making hair big white chunks

angstyg

I know it's my rim lights causing this, I'm just not sure how to fix it. Is there a setting on either the hair or lights or render settings (I'm using Iray) that can prevent the lights doing this? Or do I just need to more strategically place my lights?

Any advice appreciated!

Richard Haseltine

This is the way Iray handles lights when Draw Emitter is off - you don't see them viewed directly, but they do show in reflections and - the crucial point here - when viewed through another surface. You are seeing the light emitter where the hair mesh is in front of it and not elsewhere. As far as I know it is not possible to chnage this behaviour, a work around is to use an emissive surface and to make the Cutout Opacity value very small but not zero.

angstyg

Ah, thanks, Richard! I figured it was one of those situations where it was working as intended, lol. I'll read up on emissive surfaces, because that last sentence was... certainly words. Good, solid, Latin-like words :D

vwrangler

The issue, in part, is that you're using a shaped spot/point light as a backlight for hair that uses transparency maps (transmaps). Iray does not like shaped lights behind a transmap, of the sort that most hair of any length will have. Judging from the edge, your light a square/rectangle shape. You can mute the effect somewhat by changing it to a point, rather than an actual shape, though that changes the effect, and has its own limits.

This image and the first two paragraphs of the text underneath somewhat explain the issue, to the extent that I understood it.

angstyg

@vwrangler This info was a ginormous help, thanks so much!