Creating a Shellac Material

The Shellac material blends the colors of two sub-materials according to the amount of light falling on the surface, and the amount that you blend the materials together. In the Shellac Basic Parameters rollout, Base Material is the starting color and Shellac Material is the material that blends with the base. Shellac Color Blend controls the amount of shellac that blends.

The shellac effect is demonstrated on a vase in Figure 9.17, where the base material uses a Smoke map and the shellac material uses a Swirl map. The base material shows through more strongly when light on the object is more intense. As the surface gets darker, the shellac material becomes stronger; it predominates in indirect light.

FIGURE 9.17  A vase mapped with a Shellac material

Shellac materials introduce subtle variations to a surface, not unlike real shellac. Let’s create a shellac material:

1.  In the Material Editor, create a Shellac material by clicking the Type button and selecting Shellac from the list of materials.

2.  Click the Base Material button.

3.  Create a material of any type for the base level material.

4.  Click Go to Parent or use the Material/Map Browser to return to the top level of the material.

5.  Click the Shellac Material button.

6.  Create a material of any type for the shellac material.

7.  Return to the top level.

8.  Set the amount that you want to blend the Shellac into the base.

9.  Render the scene.

New Materials Features in Release 3

In Release 3 of MAX, the Material Editor has been completely revamped, with some powerful additions. In Chapter 8 we discussed the new Anisotropic and Multi-Layer shaders, for example, which give us precise control over the shape and orientation of the specular highlight in order to simulate things like brushed metals or to create exaggerated highlights for special effects. We also now have extensive control over the output of a particular map, as well as three new supersampling methods for improving anti-aliasing.

Altering Map Outputs

If you check Enable Color Map under the Output rollout for any map, you can access the output curve for the map, as shown in Figure 9.18. This allows you to adjust the contrast and color of the map, as it applies to that particular map usage, without changing any of the actual pixels of the map. This is equivalent to taking a single map into Photoshop, adding different adjustment layers to change its curves for different purposes, and telling MAX which adjustment layer to apply to which particular use of the map—all without opening Photoshop! It is tremendously powerful.

The tools for adjusting the output curve are all tools we have seen before in other contexts: Move Point, Scale Point (moves vertically), Add Point (corner or Bezier), and Delete Point. The X icon resets the curve to where you started. If you check RGB, you can set curves for the red, green, and blue channels. The R, G, and B buttons toggle on and off the curve for their respective channels. If you check Mono, you can work just on the grayscale value, to change contrast.

FIGURE 9.18  Output curve for a map.

Using this tool, you could use the same map in several levels of a material, applying one version of the map with the highlights emphasized to the Specular level, for example; a different, high-contrast version of the map to the Bump slot; and another version of the map with the color desaturated to the Diffuse slot—without touching a pixel of your map or having to save a single new map file. You could even apply yet another version of the map with the color balance shifted to the environment background.

Supersampling

Aliasing is the jagged edges you see in computer graphics due to a smooth edge being described by square pixels. Anti-aliasing makes the edges appear smoother by calculating intermediate pixel values along the edges. MAX calculates anti-aliasing in several levels: shadows are anti-aliased, for example, as are ray-trace reflections, texture maps, and specular highlights. The supersampler, if turned on in the SuperSampling rollout of a material (Figure 9.19), adds another anti-aliasing pass to calculate the best solution for each pixel and relay this information to the renderer.

FIGURE 9.19  The SuperSampling rollout.

	NOTE All supersamplers turned on in the SuperSampling rollouts of materials are subject to the control in the Rendering dialog box. We will discuss global supersampling in Chapter 11.

If Enable Sampler is not checked, a pixel’s color is determined by the center of the area of the scene that it represents, often resulting in aliasing. A supersampler looks at a pixel and takes samples, at a sub-pixel level, of the area of the scene that the pixel represents. Higher sampling rates can mean higher quality anti-aliasing, but they also mean much longer rendering times. Because of this, some supersamplers are adaptive, meaning they only take the extra samples when it is really necessary to improve the anti-aliasing.

MAX 2.5 Star

In MAX R2.5, we only had one supersampling method available: what is now called MAX 2.5 Star in the SuperSampling rollout. This supersampler takes five samples, including the center of the pixel and four samples around it, and averages them together. It is not adaptive, and the regular sampling pattern can lead to aliasing problems.

Adaptive Uniform

Like MAX 2.5 Star, the Adaptive Uniform supersampler takes samples in a regular pattern, but the pattern is skewed to improve the anti-aliasing. Adaptive Uniform takes between 4 and 36 samples. It will use the lower sampling rate as long as the change in the pixels is less than the specified threshold. Above that threshold, it will use a higher rate, based on the Quality setting.

	TIP With either of the Adaptive supersamplers, don’t ever uncheck Adaptive. If you’re still getting aliasing, try lowering the threshold instead.

Hammersley

The Hammersley supersampler takes between 4 and 40 samples that are randomized on the Y axis. Irregular sampling patterns like this can lead to fewer aliasing problems. The sampling rate is based on the Quality setting and is not adaptive, so this rate is applied to all pixels.

Adaptive Halton

The Adaptive Halton supersampler offers the best of both worlds: an irregular sample pattern and an adaptive sampling rate. It takes between 4 and 40 samples per pixel. The sampling pattern is randomized along both the X and Y axes, and the higher sampling rate determined by the Quality setting is only used when needed.

Supersampling with Raytrace Materials

Don’t do it, OK? Raytrace maps and materials already calculate their own supersampling, with settings in the Global Parameters dialog box we mentioned earlier in this chapter. If you also check Enable Sampler in the SuperSampling rollout, the material will be supersampled twice, greatly increasing render time. If you are using a Raytrace map in a material that is having aliasing problems somewhere else, such as in the Bump map, you might want to enable supersampling on the material level. In general, leave it off.

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