The Lambert material carries common attributes: Color, Transparency, Ambient Color, Incandescence, Bump Mapping, Diffuse, Translucence, Translucence Depth, and Translucence Focus. In Maya, the Lambert node is considered a "parent" node. That is, Phong, Phong E, Blinn, and Anisotropic materials inherit their common attributes from the Lambert material. In each case, the attributes function in an identical manner. (For a more detailed discussion of nodes and the Transparency attribute, see Chapter 6. For information on the Bump Mapping attribute, see Chapter 9.) Maya's Lambert material uses a diffuse-reflection model in which the intensity of any given surface point is based on the angle between the surface normal and light vector. In order for Maya's Lambert material to smoothly render across polygon faces, it borrows from other shading models, such as interpolated or Gouraud shading. With Gouraud, the intensity of any given point on a polygon face is linearly interpolated from the intensities of the polygon's vertex normals and two edge points intersected by a scan line.

Calculations involving diffuse reflections utilize Lambert's Cosine Law. The law states that the observed radiant intensity of a surface is directly proportional to the cosine of the angle between the viewer's line of sight and the surface normal. As a result, the radiant intensity of the surface, which is perceived as surface brightness, does not change with the viewing angle. Hence, a Lambertian surface is perfectly matte and does not generate highlights or specular hot spots. Physically, a real-world Lambertian surface has myriad surface imperfections that scatter reflected light in a random pattern. Paper and cardboard are examples of Lambertian surfaces. The law was developed by Johann Heinrich Lambert (1728–77), who also served as the inspiration for the Lambert material's name.

The term diffuse refers to that which is widely spread and not concentrated. Hence, the Diffuse attribute of the Lambert material represents the degree to which light rays are reflected in all directions. A high Diffuse value produces a bright surface. A low Diffuse value causes light rays to be absorbed and thereby makes the surface dark.

The Ambient Color attribute represents diffuse reflections arriving from all other surfaces in a scene. To simplify the rendering process, the diffuse reflections are assumed to be arriving from all points in the scene with equal intensities. In practical terms, Ambient Color is the color of a surface when it receives no light. A high Ambient Color value will cause the object to wash out and appear flat.

The Incandescence attribute, on the other hand, creates the illusion that the assigned surface is emitting light. The color of the Incandescence attribute is added to the Color attribute, thus making the material appear brighter.

The Translucence attribute simulates the diffuse penetration of light into a solid surface. In the real world, you can see this effect when holding a flashlight to the back of your hand. Translucence naturally occurs with hair, fur, wax, paper, leaves, and human flesh. Advanced renderers, such as mental ray, are able to simulate translucence through subsurface scattering (see Chapter 12 for an example). Maya's Translucence attribute, however, is a simplified system. The higher the attribute value, the more the scene's light penetrates the surface (see Figure 4.2).

Figure 4.2. Different combinations of Translucence, Translucence Depth, and Translucence Focus attributes on a primitive lit from behind. This scene is included on the CD as translucence.ma.

A Translucence value of 1 allows 100 percent of the light to pass through the surface. A value of 0 turns the translucent effect off. Translucence Depth sets the virtual distance into the object to which the light is able to penetrate. The attribute is measured in world units and may be raised above 5. Translucence Focus controls the scattering of light through the surface. A value of 0 makes the scatter of light random and diffuse. High values focus the light into a point.

The Phong shading model uses diffuse and ambient components but also generates a specular highlight based on an arbitrary shininess. In general, specularity is the consistent reflection of light in one direction that creates a "hot spot" on a surface. With the Phong model, the position and intensity of a specular highlight is determined by reading the angle between the reflection vector and the view vector (see Figure 4.3). A vector, in this situation, is a line segment that runs between two points in 3D Cartesian space that represents direction. (For a deeper discussion of vectors and vector math, see Chapter 8.)

Figure 4.3. A simplified representation of a specular shading model

If the angle between the light vector and the surface normal is 60 degrees, the angle between the reflection vector and the surface normal is also 60 degrees. In this way, the reflection vector is a mirrored version of the light vector. If the angle between the reflection vector and view vector is large, the intensity of the specular highlight is either low or zero. If the angle between the reflection vector and view vector is small, the intensity of the specular highlight is high. The speed with which the specular highlight transitions from high intensity to no intensity is controlled by the Cosine Power attribute. The higher the Cosine Power value, the more rapid the falloff, and the smaller and "tighter" the highlight.

Both Gouraud and Phong shading models produce specular highlights. However, Phong produces a higher degree of accuracy, particularly with low-resolution geometry. As with the Gouraud technique, Phong reads vertex normals. Phong goes one step further, however, by interpolating new surface normals across the scan line. The angle between a surface normal at the point to be rendered (c) and the light vector determines the intensity of that point (see Figure 4.4).

Figure 4.4. A simplified representation of the Phong shading model

Ultimately, 3D specular highlights are an artificial construct. Real-world specular highlights are reflections of intense light sources (see Figure 4.5).

Figure 4.5. (Top left) A classic specular highlight appears on an eye. (Top right) A closer look at the eye reveals that the specular highlight is the reflection of the photographer's light umbrella. (Bottom left) A glass float with a large specular highlight. (Bottom middle) With the exposure adjusted, the float's specular highlight is revealed to be the reflection of a window. (Bottom right) The window that creates the reflection.

The Blinn shading model borrows the specular shading component from the Phong model but treats the specular calculations in a more mathematically efficient way. Instead of determining the angle between the reflection vector and view vector, Blinn determines the angle between the view vector and a vector halfway between the light vector and view vector. This frees the specular calculation from specific surface curvature. In practical terms, you can make the Maya Phong and Blinn materials produce nearly identical highlights (see Figure 4.6). Maya's Blinn material uses the Eccentricity attribute to control specular size and the Specular Roll Off attribute to control specular intensity.

When it comes to the position of the specular highlight, both Phong and Blinn re-create Fresnel reflections, whereby the amount of light reflected from a surface depends on the angle of view (which is the opposite of diffuse reflections). That is, when the view changes, the highlight appears at a different point on the surface (see Figure 4.7).

Figure 4.6. Small and large specular highlights on Blinn and Phong materials. This scene is included on the CD as blinn_phong.ma.

Figure 4.7. Specular highlights appear at different points on the medallion as the view changes.

Maya's Phong E material is a variation of the Phong shading model. Phong E's specular quality is similar to both Phong and Blinn. The Roughness attribute controls the transition of the highlight core to the highlight edge. A low Roughness value will cause the highlight to fade off quickly, whereas a high Roughness value causes the highlight to have a diffuse taper in the style of a Blinn material. The Highlight Size attribute controls the total size of the highlight. The Whiteness attribute allows an additional color to be blended into the highlight between the colors established by the Color and Specular Color attributes. The Specular Color attribute is the color of the highlight at its greatest intensity.

Blinn, Phong, and Phong E highlights will become distorted as they approach the edge of a surface with a high degree of curvature. In addition, Blinn, Phong, and Phong E produce elongated highlights on cylindrical objects (see Figure 4.8).

Figure 4.8. Blinn, Phong, and Phong E materials assigned to primitive spheres, cylinders, and planes. This scene is included on the CD as blinn_phong_cylinders.ma.

When comparing the material's highlights to photographs of real-world equivalents, it's apparent that the Blinn, Phong, and Phong E models are fairly realistic (see Figure 4.9). Phong and Phong E materials do have a slight advantage on the edge of a spherical surface, where specular reflections naturally grow in width.

Figure 4.9. (Left) Various cylindrical objects lit by a single overhead light. (Right) A billiard ball with specular reflections of windows on its top edge.

The anisotropic shading model produces stretched reflections and specular highlights. The model simulates surfaces that have microscopic grooves, channels, scratches, grains, or fibers running parallel to one another. In such a situation, specular highlights tend to be elongated and run perpendicular to the direction of the grooves. The effect occurs on choppy or rippled water, brushed, coiled, or threaded metal, velvet and like cloth, feathers, and human hair (see Figure 4.10).

Figure 4.10. Anisotropic specular highlights on water, metal, and hair

The anisotropic shading model is opposite that of isotropic shading models used by such materials as Blinn or Phong. With isotropic models, the quality of the specular highlight does not change if the assigned surface is moved or rotated. With anisotropic models, a change in the surface's translation or rotation can significantly alter the resulting highlight. As a simple demonstration, two NURBS spheres are assigned to default Blinn and Anisotropic materials and are translated and rotated (see Figure 4.11).

Figure 4.11. The specular highlight of an Anisotropic material changes with translation and rotation of the assigned sphere on the right. This scene is included on the CD as anisotropic_spin.ma. A QuickTime movie is included as anisotropic_spin.mov.

CDs and DVDs produce strong anisotropic highlights due to their method of manufacture. You can re-create these in Maya with the following steps:

Figure 4.12. The anisotropic highlight of a CD is re-created in Maya. This scene is included on the CD as anisotropic_cd.ma.

The Anisotropic attributes work in the following way:

For information on raytracing and an additional example of an Anisotropic material used to create the specular highlights on glass, see Chapter 11.

Maya's Shading Map material remaps the output of another material. In other words, the Shading Map discreetly replaces the colors of a material, even after the qualities of that material have been calculated. In a basic example, the Out Color attribute of a Blinn material is mapped to the Color of a Shading Map material (see Figure 4.13). The Out Color of a Ramp texture is mapped to the Shading Map Color of the Shading Map material. In turn, the Shading Map material is assigned to a polygon frog. Where the Blinn material normally shades the model with a dark color, the bottom of the Ramp is sampled. Where the Blinn normally shades the model with a light color, such as a specular highlight point, the top of the Ramp is sampled.

Figure 4.13. A polygon frog is assigned to a Shading Map material. A simplified version of this scene is included on the CD as shading_map.ma.

Maya's Surface Shader material is a "pass through" node. That is, the material was designed to make arbitrarily named inputs recognizable to the renderer. The material does not contain shading properties and will not take into account any light or shadow information. A surface assigned directly to a Surface Shader material appears self-illuminated. Any texture mapped to the Out Color attribute of the Surface Shader comes through the render with all its original vibrancy intact (see Figure 4.14). This makes the Surface Shader ideal for background skies and brightly lit signs. The material is also well suited for custom cartoon materials in which shadowing and highlights are provided by a custom network and not by actual lights. For a cartoon material example, see Chapter 7.

Figure 4.14. A plane assigned to a Blinn material picks up shadows and highlights, whereas a plane is assigned to a Surface Shader material and ignores all lighting information. This scene is included on the CD as surface_shader.ma.

Maya's Use Background material allows the assigned surface to pick up color from a camera's Background Color attribute or image plane. For example, in Figure 4.15 a photo of a quiet town is loaded into the default persp camera as an image plane (choose View > Image Plane > Import Image from the camera's workspace view menu). A NURBS plane is aligned to the perspective of the photo's street. The plane is assigned to a Use Background material. The resulting render places the shadow of a polygon craft on top of the street.

Figure 4.15. The Use Background material is assigned to a primitive plane, thus placing a shadow on a photo of a street. A simplified version of this scene is included on the CD as use_background.ma. The image is also included in the textures folder as street.tif.

If the image plane is removed from the camera and the polygon craft is assigned to a 100 percent transparent Lambert material, the shadow is rendered by itself and appears in the alpha channel (see Figure 4.16). This offers an excellent means to render shadows out on their own pass. If shadows are rendered separately, you can composite them back onto a static background. For an example of this technique, see Chapter 10. For more information on alpha channels, see Chapter 6.

Figure 4.16. The Use Background material isolates a shadow in the alpha channel. A simplified version of this scene is included on the CD as background_shadow.ma.

The Use Background material also serves as an "alpha punch" that cuts holes into other objects. For this to work, the camera's Background Color attribute (found in the Environment section of the camera's Attribute Editor tab) should be set to black. For example, in Figure 4.17 three polygon gorillas stand close together, partially occluding each other. In a first render pass (see the top of Figure 4.17), a Use Background material is assigned to the center gorilla while the other surfaces are assigned to several Blinn materials. As a result, the center gorilla cuts a hole into the other two. As a second render pass (see the middle of Figure 4.17), the Use Background material is assigned to the two outer gorillas and the ground plane. The center gorilla is assigned to a Blinn. As a result, the two outer gorillas cut a hole into the center gorilla. When the two render passes are brought into a compositing program, they fit together perfectly (see the bottom of Figure 4.17). This works whether the objects are static or are in motion. When used in this fashion, the Use Background material allows characters and objects in a scene to be rendered separately without any worry of which object is in the front and which is in the back.

Figure 4.17. The Use Background material cuts holes into the alpha of two renders. When the renders are composited back together, they fit perfectly. A simplified version of this scene is included on the CD as background_alpha.ma.

The Cloth texture is unique in that it generates interlaced fibers. Aside from obvious use in clothing, it can be adjusted to generate various organic patterns such as reptile scales. For example, in Figure 4.18 a Cloth texture is mapped to the Bump Mapping attribute of a Blinn material.

Figure 4.18. The Cloth texture is adjusted to create scales. This material is included on the CD as cloth_scales.ma.

The regularity, or irregularity, of the cloth pattern is controlled by ten attributes. Gap Color, U Color, and V Color set the color of the virtual threads. U Width and V Width determine the width of the threads in the U and V direction. U Wave and V Wave insert wave-like distortion into the cloth pattern. Randomness harshly distorts the pattern in the U and V directions. Width Spread randomly changes the thread widths. Bright Spread randomly darkens of lightens the thread colors.

By default, the Water texture produces overlapping wave patterns. Although the default is not particularly suited for realistic liquid, you can adjust the attributes to create other patterns found in nature. For example, in Figure 4.19 a Water texture is applied to a plane as a bump map and is adjusted to emulate wind-blown sand.

Figure 4.19. (Left) Wind-blown sand forms patterns on a dune. (Right) A 3D facsimile utilizing the Water texture. This scene is included on the CD as water_sand.ma.

Critical attributes of the Water texture include:

The Concentric Ripple Attributes section sets aside another ten attributes for creating and controlling circular ripples. You can isolate the concentric ripples by setting Number Of Waves to 0.

In addition, you can use the Water texture to distort flags and other cloth-like surfaces. For example, in Figure 4.20 a Water texture is mapped to the Bump Mapping attribute of a Blinn material. The Repeat UV attribute of the Water's 2D Placement utility is kept below 1 in the U and V direction.

Figure 4.20. A Water texture is applied to a plane as a bump map, giving the cloth texture extra dimension. This scene is included on the CD as water_cloth.ma.

Perlin noise was invented by Ken Perlin in the early 1980s as a means of generating random patterns from random numbers. You can use Perlin-based 2D textures to break up surface regularity. For example, you can map the Maya Noise texture to a material's Specular Color to make a specular highlight appear more irregular (see Figure 4.21).

Figure 4.21. (Left) A Blinn assigned to a polygon frog shows little variation in the specular highlight. (Right) A Noise texture mapped to the Specular Color of the same Blinn produces a more complex result. A simplified version of this scene is included on the CD as specular_noise.ma.

In addition, you can map a Noise texture to a File texture's Color Gain to dirty up an otherwise clean bitmap. For an example, see "Stacking Materials and Textures" later in this chapter.

Maya's Fractal texture is a more complex variation of classic 2D Perlin noise in which turbulence (the averaging of multiple scales) is added for detail. The majority of attributes are identical to the Noise texture. The attribute list for both the Noise and Fractal texture is quite long but will be detailed in Chapter 5.

Maya's Mountain texture, on the other hand, is a variation of Perlin noise that lacks a smoothing function. It simulates a simplified mountain range where snow occurs at a particular elevation (as viewed from above). Although it's not possible to create a realistic mountain with the Mountain texture, you can use the texture to create granular patterns. For example, in Figure 4.22 two Mountain textures are respectively mapped to the Color and Bump Mapping attributes of a Phong material, creating the illusion of green debris and scum on a floor. A Checker texture is mapped to the Snow Color of the Mountain connected to the Phong's Color attribute, thus providing the red and white tiles.

The Mountain texture's unique attributes follow:

Figure 4.22. A Mountain texture creates green debris and scum on a floor. This scene is included on the CD as mountain_dirt.ma.

The Ramp texture allows selected colors to transition in the U or V direction. The texture carries a total of nine ramp Type attribute options and seven Interpolation attribute options, supporting a wide range of results (see Figure 4.23).

Figure 4.23. Unusual combinations of ramp types and interpolations. These textures are included on the CD as ramps.ma.

Importing custom bitmaps, whether as File, PSD File, or Movie textures, is the most powerful way to achieve realism and detail in Maya. File textures are used extensively in the custom shading networks demonstrated in Chapters 5 through 7. Movie textures are simply variations of File textures. Movie textures will read any movie format supported by Maya, including Windows Media Player AVI files on Windows systems and QuickTime on Macintosh systems. In order to use all the frames contained within the movie, you must check the Use Image Sequence attribute. Both File and Movie textures are able to accept numbered image sequences. Once again, Use Image Sequence must be checked for all the frames to be read.

Square textures are generated by repeating color blocks or lines in the U and V directions. Square textures include Bulge, Grid, and Checker. The Bulge texture can be thought of as a blurry Grid texture. Both Bulge and Grid are often useful for bump mapping. If either the U Width or V Width attribute of the Grid texture is set to 0, parallel grooves are generated in one direction. The Checker texture is handy for checking UV distortions on surfaces (see Chapter 9).

By default, many Maya textures are filtered, whether they are procedural or bitmap. This is necessary to prevent aliasing problems. In general, aliasing artifacts occur when the detail contained within a texture is smaller than corresponding screen pixels. The problems are most noticeable when textures have a high degree of contrast and the camera or surface is in motion. In this situation, a moiré pattern is often formed (see Figure 4.24 for an extreme example). Although many of the anti-aliasing attributes in the Render Settings window reduce such problems (see Chapter 10), texture filtering remains a necessity of the 3D process.

In Maya, the filtering process is controlled by the Filter and Filter Offset attributes, found in the Effects section of the texture's Attribute Editor tab. Filter forces the renderer to employ a lesser or greater degree of filtering. In essence, filtering averages the texture pixels, thus blurring the texture. The lower the Filter value, the lesser the degree of filtering and the sharper the texture. The higher the Filter value, the greater the degree of filtering and the blurrier the texture. You can stylistically add or subtract detail from a texture by adjusting the Filter attribute. For example, in Figure 4.25 the effect of a large Filter value is a blurry Grid texture. Whereas Filter controls the degree of filtering in camera space, Filter Offset controls the amount of blur in texture space. In practical terms, the Filter Offset value is added to the Filter value for an extra degree of blurring.

Figure 4.24. Moiré patterns formed by texture details that are smaller than corresponding screen pixels

Figure 4.25. A Grid texture with six different Filter and Filter Offset settings. This scene is included on the CD as grid_filter.ma.

File, Movie, and PSD File textures offer additional controls for the filtering process. You can set the Filter Type attribute, found at the top of the textures' Attribute Editor tab, to Off, Mipmap, Quadratic, Quartic, Gaussian, and Box.

Off turns off the filtering process and removes the Filter and Filter Offset attributes. Although this will speed up the render, moiré and stair-stepping artifacts will most likely appear.

Mipmap applies the mipmapping process. In this case, Maya stores averaged color values for multiple sizes of each texture. The sizes linearly decrease (for example, 512 × 512, 256 × 256, 128 × 128, and so on). When the renderer tackles an individual screen pixel, it determines the most appropriately sized mipmap. If the pixel falls over a distant surface, it recalls a small size. If the pixel falls over a surface in the immediate foreground, it recalls a large size. The angle between the surface and the camera is part of the equation. An oblique surface (one that is not perpendicular to the line of sight) induces a smaller mipmap, and a non-oblique surface induces a larger one. To increase the accuracy of the mipmap selection, Maya often averages a consecutive pair of mipmaps (for example, 512 × 512 and 256 × 256).

Gaussian shares its name with filters common to digital paint programs, such as Adobe Photoshop. Gaussian filters blur an image by convolving an array representing the original image and a second, smaller array known as a kernel. In simple terms, convolution allows the arrays to be multiplied together by "sliding" the kernel across the image array. The kernel itself contains a bell-shaped distribution of values that causes a predictable effect on different frequencies within the image. Higher frequencies equate to small details. Low frequencies equate to large image features. The end effect of a Gaussian filter is a blur that softens fine details without destroying large image features or negating edges.

Quadratic and Quartic are approximations of the Gaussian filter type that employ different bell-shaped distributions in their kernels. Both filters are optimized for speed. Quadratic offers the best balance of efficiency and quality, and is therefore the default option for Filter Type.

Box is the simplest filtering option available. Box gives equal weight to all sampled image pixels; hence, it does not preserve edges as well as other filter types. As a comparison, a TIFF image of a street is loaded into a File texture (see Figure 4.26). The File texture is mapped to the Out Color attribute of a Surface Shader material, which is assigned to a plane. The plane is rendered with Off, Mipmap, Quadratic, and Box Filter Type options. Off produces the most contrast; unfortunately, the sharp edges are likely to cause stair-stepping artifacts when the camera or plane is animated. Mipmap produces a softer result while allowing the building's "Meat Market" sign to be fairly readable. Quadratic is very close to Mipmap, but offers a slight increase in edge contrast. In this example, Quadratic erodes away the center horizontal line of the sign's first "E." Box creates the blurriest result, which make the sign difficult to read. In addition, Box creates harsh kinks in vertical lines. In particular, the left vertical edge of the sign has a severe stair-step artifact.

Figure 4.26. Detail of a 1024 × 768 bitmap, loaded into a File texture and rendered with four Filter Type options. This scene is included on the CD as filter_comparison.ma.

Two extra attributes are available to File, Movie, and PSD File textures: Pre Filter and Pre Filter Radius. Pre Filter, if checked, applies additional image-space filtering to the loaded map. The filtering occurs before any other operation is applied to the map. The higher the Pre Filter Radius value, the blurrier the image.

The Invert check box, found in the Effects section of a texture's Attribute Editor tab, inverts the colors of the texture. The result is identical to the Reverse utility (see Chapter 8). If a color is pure white (RGB: 1, 1, 1), the inverted result is black (RGB: 0, 0, 0). If a color is yellow (RGB: 1, 1, 0), the inverted result is blue (RGB: 0, 0, 1). You can predict the results by picking an opposite side of the Maya color wheel.

The Color Remap Insert button, also found in the Effects section, attaches an Rgb To Hsv utility and a Ramp texture to the shading network. The new network color-shifts the original texture (see Figure 4.27). The portion of the texture that has low color values is given colors from the bottom of the Ramp. The portion of the texture that has high color values is given colors from the top of the Ramp. If you change the Ramp colors, the colors of the texture automatically change. (See Chapter 6 for a demonstration of the Rgb To Hsv utility in a custom network.)

Figure 4.27. The result of an activated Color Remap Insert button as applied to a File texture. This scene is included on the CD as color_remap.ma.

For realistic wood, it's best to use an actual photo or scan. However, if a decent photo or scan is not available, you can generate the illusion of wood grain by adjusting the UV tiling of an otherwise inappropriate bitmap. For example, in Figure 4.31 rusty.tif is loaded into a File texture, which in turn is mapped to the Color attribute of a Blinn material (named Wood).

Figure 4.31. (Top left) 3D wood. (Top right) Reference photo of wood. (Bottom) Wood shading network. This scene is included on the CD as wood.ma.

The Blinn has the following custom settings:

The File texture's 2D Placement utility has the following custom settings:

The Noise UV attribute creates subtle distortions in the File texture, making the texture repeat less obvious. The Mirror U and Mirror V attributes flip the texture each time it's repeated, adding even more variety. In addition, the Color Gain of File texture is tinted brown. The Filter Offset of the File is set to 0.02, which softens the texture slightly. The File texture is also applied as a bump map. The Bump 2D utility's Bump Depth value is set to 0.005.

Metal is perhaps the most difficult surface to re-create. Chrome, polished silver, stainless steel, and similar metals can be reproduced with raytraced reflections. (See Chapter 11 for raytracing tips.) Many metal finishes, however, do not create coherent reflections. In such a situation, believability comes from the metal's color and the contrast of the metal to its specular highlight. For instance, cast iron is a very "dark" metal. Although iron has a moderately bright secular highlight, the section of the surface that does not receive direct light becomes dark quickly. In this situation, the iron is a poor light reflector. You can create this look by creating a dark surface color with a diffuse specular highlight. For example, in Figure 4.32 a Blinn material is assigned to a torus with the following custom settings:

Figure 4.32. (Top left) 3D iron. (Top middle) Blinn material settings. (Top right) Reference photo of iron. (Bottom) Iron shading network. This scene is included on the CD as iron.ma.

The rusty.tif file is loaded into three File textures. The first File (file1) is mapped to the Bump Mapping attribute of the Blinn material (named Iron). The Bump 2D utility's Bump Depth value is set to 0.01, creating a subtle roughness to the surface. The Placement 2D utility for file1 has its Repeat UV set to 2, 1. The second File texture (file2) is mapped to the Blinn's Color. The Color Gain of file2 is lowered to darken the bitmap and thereby reduce the contrast visible as a color. When a File texture is mapped to the Blinn's Color, more variation is present in the render than could be provided by a solid color. The third File (file3) is mapped to the Blinn's Reflected Color. The Reflected Color attribute creates the illusion of reflection without the need to raytrace. The Filter Offset of file3 is set to 0.5, blurring the bitmap. The Invert attribute of file3 is checked, thereby tinting the surface color blue and reducing the contrast. With these settings, the Reflected Color attribute creates a subtle, bluish ambient reflection across the surface. The Reflectivity attribute controls the strength of the Reflected Color effect. Last, a Ramp texture is mapped to the Specular Color of the Blinn. The Ramp has the following custom settings:

The Ramp has five handles running from black to light gray. This creates a light band across the center of the torus.

Plastic should never be thought of as a solid color. Even the most finely manufactured plastic product will contain numerous surface imperfections and variations in the specularity. The quickest way to emulate dark plastic is to apply a bitmap as a bump and a specular color. For example, in Figure 4.33 rusty.tif is loaded into a File texture (named file1). The Color Offset of file1 is set to a light blue, which reduces the bitmap's contrast; file1 is mapped to the Specular Color attribute of a Blinn material (named Plastic), which is assigned to a sphere.

The 2D Placement utility for file1 has the following custom settings:

The combination of a high Repeat UV value with a relatively high Noise UV value creates very small, near-random detail. Stagger, when checked, offsets each repeat by the half-length of the texture, creating an even more uneven pattern. rusty.tif is also loaded into a second File texture (file2), which is mapped to the Bump Mapping attribute of the Blinn. The Bump 2D utility's Bump Depth is set to 0.01. The 2D Placement utility of file2 also has a high Repeat UV value of 20, 20, a Noise UV value of 0, 0.005, and a Rotate UV value of 90. Last, the Color of the Blinn itself is set a dark gray. The Blinn has the following custom settings:

Figure 4.33. (Top left) 3D plastic. (Top right) Reference photo of plastic. (Bottom) Plastic shading network. This scene is included on the CD as plastic.ma.