How to tackle foam rubber

[isoparmesan]

Every once in a while I have to work on a scene that involves foam rubber. I normally just make some sort of noise normal map/spec map and it's usually passable, but I'm never able to really capture those little nooks and crannies.

so, I'm curious how other people tackle this. Is there a volumetric shader that could do it? Are there ways to generate that kind of geometry? Modeling it by hand is basically out of the question, it's possible, but wouldn't be worth the effort in my opinion.

I've attached pictures I pulled off google images with the type of foam I'm talking about.

funny, that googling this and searching forums has only resulted in people talking about "rendering" actual foam, as in the chemical process of making foam rubber, or people talking about ocean or beer foam shader techniques.

[super gnu]

hm.. vrayiso would have been perfect for this. was discontinued years ago.. and the closest we have got since is the metaball isosurface thing in vray 3, but that only works with particles, and hence is loads more fiddly to set up, and doesnt appear to work in quite the same way.

ive no idea why a nice isosurface constrained by a non-renderable mesh hasnt been added to vray since. vrayiso was amazing.

[isoparmesan]

I hadn't explored VRayMetaball. Seems like that combined with a bump/normal map might do the trick. I'll look into it.

[super gnu]

i was quite excited about vraymetaball. but it doesnt seem able to handle the incredibly finely detailed stuff that vrayiso was capable of. its all quite...blobby. maybe i need to test again.

also its a PITA to have to generate a particle system just to fill a volume with an isosurface. it gives loads more variables to deal with when setting up your effect.

[cheerioboy]

I know you're using Maya, but I thought I'd try my hand at this in 3dsmax. There's a perfect material for this called Cellular with a 'Chips' cell characteristic. Used it for displacement. It looks pretty close! With the top surface using the same texture but with a bit of grey multiplied in to lessen the effect. I'd think you could make a nice material/texture to achieve this.