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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
The mental ray render is integrated as a plug-in into Maya, but you can still use standard Maya shaders when rendering scenes with mental ray. So for example, in this scene I have a number of teapots and each one has a different Maya shader applied to it. I'll take a brief look at how some of these shaders work. Here's the scene right here. On this teapot in the far left I have a Lambert shader applied. Lambert shader is good for diffuse surfaces. So when light hits the surface it's reflected in all directions, creating kind of a matte like quality to the render.
So you look at the render right here. This is what Lambert shader looks like. So there's no reflection or specular highlight on Lambert shaders. It's just essentially a diffuse control. So I can control the intensity of the diffuse reflections using the Diffuse slider. I'm just moving this up and down and you can see how the surface becomes lighter or darker. Next to this teapot I have a teapot with Blinn shader applied. Blinn shader is one of the most commonly used shaders and you can use it with mental ray.
It's good for simulating various types of shiny metal. It has a nice broad highlight with a nice falloff to it. You can see this is the Blinn render right here and it's also reflective. Like the Lambert shader it has a Diffuse setting as well and then to control the specular highlight and reflectivity you want to go down to the Specular Shading section. So by decreasing the Eccentricity you get a tighter highlight. You can then control the Specular Color, make it more or less intense, and also the Reflectivity, how much it reflects the environment.
Now a couple things to note and this sort of a general statement about many of the Maya shaders. You have a separate setting for Diffuse and Reflective qualities and also the Reflective qualities are split between controls for the highlight and the overall reflection. This is to allow you more flexibility when designing a shader. In the real world the more diffuse a surface is, the less it won't precisely reflect the environment, because the diffuse quality is essentially as the surface it becomes more rough it diffuses light into the environment.
So you see less of the reflection of the environment on the surface. But in this shader there are separate controls, and this allows you to create the look of maybe like a layered material. So something that might have a diffuse layer and then on top of that kind of like a glossy coating. The reason we have this separate controls for this specular highlight in the Reflectivity is that CG lights are actually emanated from an infinitely small point in space. So if I was to do a realistic reflection of a CG light source, it would end up being a very, very tiny dot.
Maybe even less than a pixel in size. So by adding a separate specular control it's kind of a cheat that allows you to create the look of a reflected light source on this surface without being necessarily physically accurate. This again is just to give you more control over when you're designing a particular type of shader. Next to the teapot with the Blinn shader I have Ramp shader. If you look in the Attribute Editor for the Ramp shader you can see that there are various color ramps that are designed to control the qualities of the shader for the Color, Transparency, Incandescence, the Specular Color, Specular Rolloff, and Reflectivity, how much it reflects the environment.
In this case these two settings use a graph. You can expand this graph by clicking on this little icon here. It's the one where I get more control over editing it. The way in which the ramps and the graphs are controlled is determined by the Color Inputs setting. So for this particular shader I have Facing Angle. So this is to simulate like sort of Fresnel types of reflections. I've selected this color marker here on this side of the ramp. I clicked on the Selected Color swatch and just use the color chooser to add a dark blue and I'm going to click on the second color input.
Click in the color swatch and add a different color, like maybe a deep red. You can see in the preview here that since this is set to Facing Angle, the parts of the surface that face the camera are red; the parts of the surface that face away are dark blue. But you can also choose things like Light Angle, Surface Brightness, Normalize Lightness, that keeps the brightness within range of 0 to 1. These are different ways to determine the ramp shader. Ramp shaders are good for various types of special effects, but you can use them for a variety of surfaces as well.
The Anisotropic shader is a standard Maya shader that simulates anisotropic reflectivity and specular highlights. In other words, surfaces that have microfacets on them, like a CD or a satin pillow or something like that. If you open the Attribute Editor for the Anisotropic shader, you'll find the controls for editing the specular highlight under the Specular Shading section and you can control things like the Angle, the Spread in order to control the tightness of the highlight on the surface, Roughness, Fresnel Index.
So how much the highlight reflects based on the incidence angle or the angle of view that you're viewing the surface. If you look at our render here, here's the Anisotropic shader and you can see how this highlight is sort of stretched out here. In the back here I have two teapots with the Phong and Phong E shader applied. These are again very useful for simulating glossy materials such as plastic and glass. So it's an alternative to using something like a Blinn shader and depending on what the surface you're trying to determine you might want to experiment using either Phong or Blinn or Phong E.
If I click on this teapot right here towards the center and this has a Phong shader applied and again the specular reflective qualities are found here in the Specular Shading section. So to control the size of the highlight you can increase or decrease the cosine power, you can change the Specular Color, the amount of Reflectivity, and so on and so forth. The Phong E is very similar to the Phong shader. It just has additional controls. You can control the Roughness of the highlight and the Highlight Size separately and also the Whiteness and the Specular Color.
The Whiteness is kind about the brightness of the highlight and then the Specular Color. I'm going to click on the swatch here and choose Green. So that's the Specular Color, but the Whiteness you can see controls kind of the intensity of the highlight. Then again we have Reflectivity, how much it reflects the environment. So if you're comfortable using the Maya standard shaders, you can use them when rendering with mental ray and you'll find for the most part you can simulate most materials using the Maya standard shaders.