mental ray Workflows in Maya: Subsurface Scattering

Gain a deeper understanding of Subsurface Scattering, how to accurately simulate light behavior, and learn a time-saving approach to lighting and rendering translucent surfaces with mental ray. Software required: Maya 8.0 and up (Maya 2008 required for project files).
Course info
Level
Intermediate
Updated
Jul 25, 2008
Duration
3h 10m
Table of contents
Introduction and Project Overview
mental ray Workflows in Maya: Subsurface Scattering
Description
Course info
Level
Intermediate
Updated
Jul 25, 2008
Duration
3h 10m
Description

Gain a deeper understanding of Subsurface Scattering, how to accurately simulate light behavior, and learn a time-saving approach to lighting and rendering translucent surfaces with mental ray. Provides over 3 hours of project-driven training for artists learning how to achieve more realistic results with Subsurface Scattering. Popular highlights include: Overview of essential subsurface scattering attributes; Connecting lightmaps to subsurface shaders; Understanding forward and backward scattering; Using bump and normal maps with subsurface shaders; Properly controlling light interaction with translucent surfaces; Controlling scatter bias; Adjusting lightmap's Diffuse Gamma Curve; Adding separate specular/reflection attributes to SSS shaders; Using SSS with final gather; Using textures to drive SSS attributes; Using the Physical SSS shader; Controlling photon interactions with Physical SSS; Absorption and scattering coefficients. Software required: Maya 8.0 and up (Maya 2008 required for project files).

About the author
About the author

Kyle was one of the first authors for Digital-Tutors (now a Pluralsight company) and has been a part of the team for over 10 years. Kyle began his career in computer graphics education as a college instructor and worked as a Digital-Tutors rendering tutor and curriculum manager since 2002.

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Section Introduction Transcripts
Section Introduction Transcripts

Introduction and Project Overview
[Autogenerated] Hello and welcome to the series of mental ray work flows in Maya subsurface scattering presented by digital tutors and auto desk authorized publisher. My name's Kyle and I'll be your instructor, guiding you through the process of using subsurface scattering and metal ray to accurately simulate the behavior of light as it interacts with translucent objects. Now, in reality, many object that we see possess some sort of translucent properties where the object is not necessarily transparent, but it does allow light to pass def, usually through it. Now these could be seen in many types of materials things like plastic wax paper and even human skin, just to name a few examples. Now, in mental ray, these types of translucent effects can be simulated with a feature called Subsurface scattering. And as we'll see that the course of this training, they're actually several types of subsurface scattering that we can use within Maya. So we'll begin our training by taking a in depth look at the subsurface, scattering attributes and understand exactly how each of these attributes works. From there, we'll start to see how we can do things like add completely new functionalities to the subsurface shade Er's without having to rely on any kind of third party nodes. And as we progress even further into the training will start to explore these practical lighting examples with a very special emphasis on light and relation to subsurface scattering. So by the end of this training, you will have a very strong understanding of not just how subsurface scattering works, but how it works with many other lighting and rendering variables. What this means is that you will have a very firm understanding of subsurface shading and lighting techniques that you can begin implementing immediately into your own projects. All right, so before we actually start to get into the process of working with these subsurface scattering shade er's one thing that I do want to do is take just a few minutes to discuss the process of actually hooking up the note networks to make the subsurface scattering work properly. All right, so the first thing we need to do is actually go into the hyper shade and add in the special notes. They're gonna be responsible for this subsurface scattering effect, so we first need to make sure we're inside the create middle ray nodes tab we won't expand the materials and kind of down toward the bottom. If you look, you should see a hand polish eaters with the sort of prefix it says M i s S s That's mental images, subsurface scattering. And as I mentioned in the introduction, you can actually see there are several different subsurface shooters to be able to choose from. So just for demonstration sake, if we were to add any of these, let's say the fast shader you can see here is our shading note. All right now, what makes subsurface scattering a little bit different from some of the other mental ray features like global illumination, final gather or cost IX, is the fact that subsurface scattering is not a result of anything that has enabled inside the render settings. Instead, subsurface scattering happens entirely on the shader itself. So making sure that the shooter is hook up correctly is going to be absolutely critical for getting your subsurface scattering now, depending on which version of my are you using? If you're using anything that is my 8.5 or older, whenever you add in the subsurface shader, it will connect or just drop in this one singular note. But in reality, this shader actually requires a few other notes to be connected into it for it to work properly. Now, if using anything that is my in 2008 or newer, those additional notes are automatically created and connected and for you. All right, So for those of you who using my 8.5 or anything older than that, we're gonna walk through the process of manually connecting in these nodes. If using anything that is 2008 or newer, you don't necessarily need to go through this process. So if you want, you can actually skip the rest of this lesson and pick up at our next one. All right, So once we have this note that's dropped into our work area, there is a couple of extra that we need to add in here. One is we need to make sure that we access this subsurface haters shading group. Right, because we're actually gonna need to make some connections into that. So quick and easy way if you go for the shading groups tab here in your hyper shade. Let's find this M I s s s shader group little click drag it down into our work area. You can see that is the actual connection. All right, so just for convenience sake, just to get a little bit more room to go ahead and click on this button here, which will just let us expand this work area. Now, one of you know that we need to add in is the light map. Right? And I'll kind of explain what these different knows you're gonna do. Once we get them connected up, it'll be a little bit easier to visualize what exactly is happening. So we're gonna add in this M i s s s fast l map. And we'll sort of get this place and over here in a little bit. Order a little bit more orderly layout here. All right, so there is actually one extra know that we need to create, which will automatically be created for us during this process. So I'm gonna go in and just hide back in myself a little bit more room to work with. The first process is if we double click on the shader. Any subs officiated. We happen to be using We want to take a look and try to find the attributes for the light map. Right? In our case for this fast Shader, it's found inside the data storage. So once we find the light map attribute, we need actually map an image into that romantic texture into that. So if you click on the checker box and go ahead and automatically make this new node called mental rate texture Okay, now, this is actually very, very important for the subsurface process, as is this extra note. So what we need to do is connect these two together. So let's take this fast. L map of this l map. Right. And we're in the area for data storage Will take the light map. We'll take this metal rate texture, middle click and connect it into the light, man. All right. And then one last connection that we need to make is on the sheeting group itself. So with a shader group selected, take a look inside the mental rate M scroll down and look for a slot called light map. Shader. That's where this L map is gonna go. So middle Click connected in. All right, so here is kind of what we've created. We kind of have this sort of looping connection here kind of this circle of consequence. So what we have is this subsurface Shater itself, which is gonna be responsible for the way that light passes through and interacts with whatever object or surface it's connected to. Now, by itself, it doesn't contain all the information. So what it does is it actually looks at the way that light should be passing through and then feeds that into this metal rate texture. Right now, this texture is gonna write out either to your hard drive or be written into memory. And from there, that data is going to be pulled back in through this light map, right? And that is gonna act sort of as the intermediary. It'll pull it in and then feed it back into the Shader itself. And then that result will be your final subsurface scattering effect. So we're very important to make sure that you have all of these notes. And like I said, if you're using my 2008 or anything newer, this entire connection is already made for you. With the moment you add your subsurface haters. All right. Now, before we call this done, there is actually a couple of options that we need to make sure that we enable correctly on this mental rate texture. So if I double click on that, you could see that there are a few options listed in here. So this metal ray texture, as I mentioned, this is the actual place holder where the light information is gonna be temporarily written to before it's red back in by this light map, right? So with this note, we need to make sure that it is able to read that information and store it correctly for use later. So the first we need to do is make sure that the texture type is set to a color. That's good. We didn't make sure this is a texture that can be written to and read from, so we need to make sure rideable has turned on. Now these options are very important. This is basically the dimensions of the file. It's gonna be written out now the way that the subsurface scattering works when it was writing out this light map is it will separately, right out the information for the light in the front of the object and the light passing through from the backside. So because you essentially have double the amount of information went for the front one for the back. Really need to make sure that this file size width is about double what your height is. And actually this is should be based on your actual render settings. So, for example, if I were to go to the render settings right now, I'm rendering out an image that 6 40 by 4 80 right these the dimensions that you want to make sure you feed correctly into this file of the light man for this metal rate texture. So for the the height, that's pretty easy. That'll be 4 80 which matches this, and we want to make sure that the width is basically double whatever we have for the actual render with. So in our case we have 6 40 It will do 12 80 right, so that gives us double the amount of information. So we have plenty of information for the front lighting information and the backlighting information to be written into this file. Otherwise, this is not necessarily essential toe have doubled with, but if you want to make sure that the results are as accurate as possible. That's a good way to go where it's a definitely rule to try to follow. And then finally, for the file size depth by default, it's gonna be set to eight bit. Normally, you would try to set this to 32 bit. So that way it can write the maximum amount of color information from the light passing through the object that we don't wind up with a clipping or anything like that. Now, with a file or the image name, we could actually define some kind of a light map that's written into the hard drive. Or if you don't find any kind of an image name, it'll just temporarily write that into RAM and then just pull that right back in without actually physically riding something out to your disk. So if you want, you can manually define an image name. Or if not, ah, it doesn't necessarily matter. All right, so that's pretty much the node network that we need in order to make ours subsurface skaters work properly. So for the duration of this training, I'm gonna be moving into my A 2008 where it will automatically make these additional notes for me as I start to add some these different subsurface shading nodes in. So just keep in mind that as you are working, if using anything older than my 2008 just make absolutely certain that once you add in one of these subsurface shading nodes that you go through the additional process of connecting in the middle right texture, setting these attributes properly, feeding that into the light map and then feeding that into the fast shader or it's shading group. All right, so now that we're familiar with exactly how to set this up, we'll start to, in our next lesson, move into my a 2008 and from there we'll start to dissect some of the various attributes that are found on these subsurface scattering shakers.