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- Understanding shading concepts
- Simulating the Fresnel effect for realistic reflections
- Rendering transparent and translucent surfaces
- Comparing mental ray and Maya standard shaders
- Introducing the mia_material
- Developing shader networks
- Using subsurface scattering shaders
- Mapping polygon UV coordinates
- Incorporating texture nodes into networks
- Improving skin detail with ambient occlusion
- Painting bump maps
- Creating normal and displacement maps
- Troubleshooting maps
Skill Level Intermediate
In this movie, we're going to talk about how you can use file textures to make your shader networks look even more realistic and add more detail. The idea is, is that have two copies of this old man character and you can see that they both have a subsurface scattering shader applied to them. But the one on the right has much less detail and does not look very realistic, kind of looks more like a plastic and the one on the left is starting to look more and more realistic. So the only real difference between the shader applied to this guy and the shader applied to this guy is that I've actually started to incorporate file textures into the Shading node.
So let's take a look here at how we can do something like this. So I am going to take the less detailed version of the model. I'll go to Window > Rendering Editors > Hypershade and I want to expand the work area. I'll right-click and choose Graph Materials on Selected Surfaces and then we can open up the Fast Skin shader here in the Attribute Editor. And for the moment I have decent settings setup, so I've already set my Back Scatter Radius and Back Scatter Weight and same with Subdermal Scatter Colors.
So I've got some basic ranges for each part of the Subsurface Scattering shader network. But you can see right now I just have flat colors in here, so just a dark red for Back Scattering, sort of a yellowish color for Subdermal, and Epidermal I have pinkish color and Diffuse is also somewhat pinkish. For Specularity I have a dull grayish blue in Primary Specular Color and a lighter white in the Secondary Specular Color. So the secret to get this to look more realistic is to start using file textures.
In other words paint by hand a texture that can have things like veins in it and areas of different colors and so on and so forth. To add a file texture to something like the back scattering color I would just click on the Texture Node here to the right of the slider and choose File and this would bring up the File node. And then I can apply one of the textures I've created by clicking on the folder next to Image Name and in the Source Images directory I have an image called hatter_backscatter.
It's called hatter because originally this character is going to be the Mad Hatter. There's no technical reason for using that name. So if I take a look at this texture, I am going to right-click on it and choose Test Texture and this will open up the texture actually in the Render view window, which I need to expand here. Now we can see the actual texture. So you can see that this texture rather than being a flat reddish color actually has a lot of variation in color. These correspond like the colors on the face. So you can see there is sort of a purplish color along the beard line. You can see where the lips are, the nose, the eyes and the ear and so forth.
It has variation, little bits of white here to break up the color to make it look a bit more interesting. So now if I render the scene, it's still a bit strange because right now I only have the one texture applied but I'll render it, and just to see how it looks. We can see how the things are starting to change. It's subtle, but you can see especially in this ear I am starting to get some detail. You can start to see some of the veins in there. There is more of a reddish color. There is more variation. It's subtle because of course it's in the Back Scattering layer and the other layers are using just simple colors.
What I can do to make this more obvious is I'll select the shader and set the weights of the other channels to zero. So Subdermal Scatter Weight I am turning to 0, Epidermal Scattering Weight I am turning to 0, Diffuse Weight I am turning to 0, and I am going to select an area here just to render that area, just so you can see it. So you can see the texture map is now affecting just the Back Scattering. If I selected this version of the old man, right-click, and choose Graph Materials on Selected you can see I've actually got a total of six different texture maps plugged into the various channels.
I have texture map for the Back Scattering, a texture map for Subdermal, a texture map for Epidermal, a texture map for Diffuse and I have two separate specular maps that are meant to break up the Specular highlights on the surface and using texture maps in the Specular channels will really start to sell the look of human skin. So now you see that using texture maps in the Subsurface Scattering network or actually any shading network will really improve the realism, it will take it beyond sort of looking CG and start to bring it into the world of reality.
But the question becomes how did I make these texture maps? Well, the answer that is simple. A lot of hard work. There are a number of ways to approach creating texture maps. You can paint texture maps in Photoshop, which is a long have been the way that texture artists have worked. You can also use other programs that allow you to paint it directly on the 3D model, your various colors. So for instance, I've personally used Zbrush to create these texture maps by painting them directly on the surface of the model. That way I don't have to worry about trying to figure how to paint in 3D in a program like Photoshop.
Other programs include Mudbox, that will also give you this capability. But if you're going to use something like Photoshop you don't have access to these programs. I want to give you some hints as to how you can get a texture started in Photoshop. So what can do is, I've actually matched the UV coordinates for these objects and that's the first thing you need is UV texture coordinates. So I'll select this old man. It doesn't matter. I could select either one. Choose Window > UV Texture Editor and currently I have a group selected. So you're seeing the UVs for the man and also his teeth.
So let me expand the old man and just select the old man shape here. So I am not selecting the teeth. So now you can see the UV texture coordinates for just old man. So you can see where his eyes are, his nose, his lips, the ears and so on and so forth. So when I have the UV texture coordinates mapped out, what I can do is I can go to Polygons menu and do UV Snapshot and say I want to make this texture 2048x2048. That determines the size.
I am going to choose the TIFF format so I can open it up in Photoshop and then I'll choose OK and this is going to save it to the Images directory. So I'll just call this OldManoutUV. Choose OK. That will save the UV texture coordinates as an image file. And now I can go into Photoshop and in the images directory of the current project, the Exercise Files project, I'll choose OldManoutUV.
Now I can see here are the UV texture coordinates and if I am going to paint something like this in Photoshop, what I'll do is I'll make a copy of the background layer, I'll create a new layer above the background layer, and fill this with just a simple color, like if I am going to the back scattering layer I might do a dark red and I will set the Background copy to Screen. So now I can see the UV texture coordinates. And now on this dark layer I'll start to paint the variations of color corresponding to the different parts of the face.
And I'll show you what these look like in Photoshop, each of these textures, so you get a good idea of how they work. So in the sourceimages directory I'll open the back scattering, epidermal, subdermal, diffuse, and the two specular maps. So looking at the back scattering, now if you can see I have variations of colors in here. So this is meant to represent you know muscle, the yellow parts, or you can just see a little bit of bone, blood vessels underneath the skin, and let me go to the subdermal.
So now you can see in the subdermal layer I have veins and age spots, a little bit more bone color, some red for their blood vessels again, definitely lot of veins in the ear. And then if I look at the epidermal, this is where I start to painting things like freckles, the lip color, more variations in skin with lighter colors for sure. And then the diffuse layer has a much lighter version of the epidermal layer and that's where I also paint a lot more freckles and that kind of things, so this is the color of the skin. And then for the specular layers, they are essentially just grayscale textures and I've added a lot of variation here and this helps to subtly break up the look of the specular highlights across the surface.
So you can see the dark areas are the parts where it going to be less reflective, we are going to see fewer specular highlights, and the lighter areas are going to be brighter areas of the specular highlights. And then I have a second spec map and this is for the shiny quality and I just have a little bit on here, so like in the oily parts of the skin, like within the ears and on the nose. But that's really the basic idea is to start to use texture maps so that your shader networks, rather than looking like plastic or just flat materials or metals and things like that, you can start to use texture maps to break up the various channels and give them much more realism to your shading networks.
So you can think of other ways that this might be used. For instance, if you're going to paint like a rusted metal you might want to use photographs and use them in your file textures to create the look of a rusted metal spots and that kind of thing. You might want to create a separate specular layer that has different shiny parts and duller parts. You know, on a mechanical object may be the corners are slightly duller than other parts because they're exposed to wear and tear. But that's the basic idea. So the secret is to use file textures to add detail to your shading networks.