How would you emulate iridescent/pearlescent materials in PBR?

Rooster128

How would you emulate iridescent/pearlescent materials in PBR? Things like bug shells, soap bubbles, oil patches, etc. I've seen many ways people emulate the look using a non-PBR workflow- by using a saturated specular map or environment map. But since PBR works on the principle of light conservation, what would be the "correct" way to go about iridescence?

EarthQuake

Iridescent/pearlescent are sort of their own thing, and would likely require a custom shader.

Soap bubbles, oil patches etc can be done with a Newton's ring shader. We have a Newton's rings specular model which can be added to the secondary reflection slot in Toolbag 2.

Check it out:

EarthQuake

Also, if you disable culling back faces in the mesh (to make it double sided) that helps.

Now the real question, what is the reflectivity of soapy water?


Top: 4% reflective
Bottom: 15% reflective

Anddd with a detail normal map and displacement map it break it up a bit. IT would be cool to have some sort of oil map or something for the Newtons ring model but this is probably as close as I can get without custom shader work.

marks

You could probably do the oil smear effect using aniso with a tangent/direction map...

But yeah, iridescent/pearlescent are kind of their own thing and almost certainly would require a custom shader

Rooster128

Thanks for the information guys. It's as I expected really- was just wondering how robust PBR might be. This Newton ring model looks really awesome!