The Glossy material is used to create shiny materials such as plastics or metals. (Figure 1). Figure 2 shows the parameters of the Glossy material in Maya's Attribute Editor.
Figure 1: An object rendered using the Glossy material.
Figure 2: The parameters for the Glossy material.
Glossy Material Options:
The Diffuse parameter gives the material its color. In computer graphics this is also referred to as “Base Color” or “Albedo”. Diffuse color can be can set using the color picker or by connecting a texture (procedural or image-based).
The Specular parameter determines the intensity of specular reflections that appear on the surface. Specular reflections are reflections of light sources on the surface. The specular input accepts color values and textures. In most cases specular highlights are white or colorless. However to simulate metallic surfaces the specular color should be tinted using a color similar to the diffuse parameter. Think of the bright yellow-orange highlights seen on the surface of a polished copper kettle.
The roughness parameter determines how much the specular reflection spreads across the surface. In CG terminology this is also referred to as “reflection blur”. A value of zero simulates a perfectly smooth reflective surface such as a mirror. Increasing the value simulates microfacets in the surface which causes the reflective highlights to spread. For example to create the look of worn plastic you would increase the roughness value. This parameter accepts a value or texture map (procedural or image-based).
Film width simulates the look of a thin film of material on the surface. This is useful when you want to create an effect such as the rainbow colors that appear on the surface of an oil slick. Larger values increase the strength of the effect.
The Film IOR controls the Index of Refraction of the thin film, use this option to adjust the colors visible in the film.
Index refers to the Index of Refraction for glossy materials determines the strength of reflections on the surface based on the Fresnel law. The Fresnel law describes the physical properties of light as it is reflected off of a surface at grazing angles. If Index of Refraction is set to a value higher than 1 the reflection will be strongest on the part of the surface that turn away from the viewer’s angle(grazing angles) while the reflection will appear weaker or less apparent on the parts of the surface that are perpendicular to the viewing angle. Since this is a physically based phenomena the result is a more realistic looking surface. If Index of Refractions is set to a value lower than 1 then the fresnel effect is disabled and the reflection color will simply appear as a uniform color across the highlight. The color of the reflective highlight itself is determined by the color connected to the specular channel.
In the following examples, the six balls have roughness 0, 0.2, 0.4, 0.6, 0.8, 1.0 (left to right) and only the specular value and index of refraction have been modified for each rendered image (see Figure 3 ):
Figure 3: Spheres rendered using different settings for specular and index. .
The Bump parameter is used to create fine details on the material’s surface using a procedural or image texture. Typically a gray scale texture is connected to this parameter, light areas of the texture give the appearance of protruding bumps, dark areas create the appearance of indentation. The strength of the bump map can be adjusted by setting the Power or Gamma values on the Octane image texture node. These attributes are covered in more detail under the Texture Overview category.
The Normal parameter is also used to create the look of fine detail on the surface. A normal map is a special type of image texture that uses red, green, and blue color values to perturb the normals of the surface at render time thus giving the appearance of added detail. They can be more accurate than bump maps but require specific software, such as ZBrush, Mudbox, Substance designer, Xnormal, or others to generate.
The Displacement parameter adjusts the height of the vertices of a surface at render time using a texture map. Displacement maps differs from Bump or Normal maps in that the geometry is altered by the texture as opposed to just creating the appearance of detail. Displacement mapping is more computationally expensive than using a bump or normal map but the results can be more realistic especially along the silhouette of the surface. Displacement mapping is covered in more detail under the Texture Overview category.
The Opacity parameter determines which parts of the surface are visible in the render. Dark values indicate transparent areas, light values determine opaque areas. Values in between light and dark create the look of semi transparent areas. You can lower the opacity value to fade the overall visibility of an object or use a texture map to vary the opacity across the surface. For example if you wanted to make a simple polygon plane look like a leaf you would connect a black and white image of the leaf’s silhouette to the opacity channel of the diffuse shader.
The Smooth parameter is a Boolean (meaning that it is a toggle that turns the feature on or off) which smooths the transition between surface normals. If this option is disabled the edges between the polygons of the surface will be sharp giving the surface a faceted look.
The Rounded Edges parameter bevels the edges of the surface at render time automatically without the need to alter or subdivide the geometry. Using this option can enhance the realism of objects by eliminating overly sharp edges. The value refers to the radius of the rounded edge. Higher values for this setting produce rounder edges.