Join David Andrade for an in-depth discussion in this video Materials and Multiscatter GGX, part of Blender: Tips, Tricks, & Techniques.
- [Narrator] Blender 2.78 introduced a brand new algorithm, multiscatter GGX that changes the way you approach materials with high-roughness. In this weeks "Tips, Tricks, & Techniques", we're going to go over how to use it and take advantage of it. Let's take a look at this beautiful, happy Buddha sitting out in Southern California at Carpinteria Bluffs. As you can see, it has this nice, glassy shader on top of it and a diffuse right below it. The glass is acting like a sea glass, it's a little rough.
You can see here that I raised the roughness to almost .7 and I'm using GGX. The downside is that it's making certain areas really, really dark. Take a look at some of these. See that? If we compare our Buddha from GGX to multiscatter GGX, the changes are immediately noticeable. Now with multiscatter GGX enabled on our glassy Buddha, you can see the changes immediately. If you look underneath the chin, you can already see how much lighter it is, especially on the mouth, and in the area behind the head.
Sure, we're going to get some dark areas right over here underneath his feet, but that's okay because you imagine with all the stuff on top of it, it would get pretty dark. But this whole foot has now a much better gradation on it, and honestly, feels more accurate. Multiscatter GGX changes the way Blender handles roughness, but honestly, it makes it look so much better. Multiscatter is also present in the new principle BSDF shader that's included in Blender. With GGX on, you can see behind the head, it looks kind of bright, doesn't it? Even underneath the feet there, in fact, right underneath the foot, if you look closely, you can see it starts to get much brighter right before it hits the shadow.
Let's turn on multiscatter and see what's actually supposed to happen. Now with the new multiscatter GGX enabled, you don't get that little brightness that was underneath here, which was actually incorrect. And if you look behind the head, it's actually correctly bouncing all the white there, so it's actually a little darker than before. That's because multiscatter requires Blender to be energy-conserving, that is, it's not putting out more light towards you, it's only putting out as much light as its given, and a little less because it's bouncing around in the object.
Multiscatter is going to change the way you approach your materials, especially ones that have a high roughness. You will get a little bit of a performance hit, about a 2% slowdown on your renders, but the difference is absolutely noticeable, because all of your materials and objects will suddenly seem more lifelike and real. I highly recommend you get in there and start experimenting with them. Now, one little caveat before we leave. You can still use GGX, it hasn't been kicked out. In fact, for materials that have very low roughness, I highly recommend it, because you don't really need multiscatter running when there's no roughness.
So if you turn down your roughness all the way, and you have a nice, shiny Buddha like this, then feel free to turn on GGX, because you honestly won't notice any difference. Until next time, this is "Blender Tips, Tricks, & Techniques."
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