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Y-axis Tiling value to 20 in the Coordinates rollout. Then click the Go to Parent button, and in the Blinn Basic Parameters rollout, increase the Specular Level to 75. Name the material Tabletop, and drag the material to the tabletop.

6.In a graphics program like Adobe Photoshop, create and save a 200×200 image with some repeating colored vertical stripes that can be used as wallpaper. Select the fifth sample slot, and click the map button to the right of the Diffuse color. In the Material/ Map Browser, double-click the Bitmap selection. A File dialog box loads, in which you can locate the wallpaper image. In the Coordinates rollout, set the U-coordinate Tiling value to 100 and drag the material to the wall plane object.

Figure 44-10 shows the rendered image.

Figure 44-10: A rendered image with raytrace materials applied to the vase and table

Using a Raytrace Map

The raytrace map is an alternative to the raytrace material discussed previously and, as a map, can be used in places where the raytrace material cannot.

The raytrace map includes several similar rollouts and several unique rollouts. In the Raytracer Parameters rollout, the Local Options section lets you select to Enable Raytracing, enable Raytrace Atmospherics, Enable Self Reflect/Refract, and use Reflect/Refract Material IDs. The Trace Mode determines how the rays are cast through the scene. Options include Auto Detect, Reflection, and Refraction. You can also use the Environment Settings or specify a color or map to use for the Background.

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Setting Raytrace parameters

The Local Exclude button opens the Exclude/Include dialog box where you can select which items to include or exclude in the raytracing calculations. The Raytracing Antialiasing dropdown list is enabled using the Global Raytracing Settings dialog box.

Note	You set global raytracing options using the Rendering Raytracer Settings menu command.

The Attenuation rollout lets you select from one of several Falloff Types. The options include Linear, Inverse Square, Exponential, and Custom Falloff. You can also set values for the Start and End distances. The Custom Falloff type lets you set a graph by adjusting Near, Far, and two Control values.

The Basic Material Extensions rollout lets you set the Reflectivity/Opacity Map and its strength. You can also set a Basic Tinting color or map. The Refractive Material Extensions rollout includes settings for specifying the Color Density (Filter color) and Fog.

Tutorial: Raytracing a wine glass

Raytracing complex scenes requires some serious processor power because each light ray that is being traced can bounce off many different objects multiple times. By applying a raytrace map to a single object, you can dramatically decrease the render time while still maintaining a quality look.

To apply a raytrace map to the glass in this scene, follow these steps:

1.Open the Table setting.max file from the Chap 44 directory on the CD-ROM.

This file includes all the meshes used for a table setting. These models were provided courtesy of Zygote Media. The materials for everything except the wine glass are already included, assigned, and visible in the Material Editor in the first four sample slots.

2.Choose Rendering Material Editor (or press the M key) to open the Material Editor.

3.Select the fifth sample slot, name the material Wine Glass, and click the map button to the right of the Diffuse color swatch to open the Material/Map Browser. In the Material/ Map Browser, double-click the raytrace map.

4.In the Raytracer Parameters rollout, select the Refraction Trace Mode option and select the Black color swatch option in the Background section.

5.Drag the “Wine Glass” material to the wine glass object in the viewport to apply the material to the object.

6.In the Material Editor, drag the “Wine Glass” material to the sixth sample slot and select the Diffuse map. Then change the Background color to White, and drag the new material to the drinking glass positioned next to the wine glass. In the Assigning Material dialog box that opens, name this material Drinking glass.

Figure 44-11 shows a place setting created by Zygote Media that includes a wine glass with a raytrace map applied.

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Figure 44-11: You can use the raytrace map to raytrace only select objects.

Enabling mental ray

If you’re accustomed to using the Default Scanline Renderer and you’re wondering if the mental ray rendering engine is good for you, the answer if yes. Actually, you should try a couple of test renderings first and play with the different settings, but in working with mental ray, I’ve been amazed at its results.

As a raytracing renderer, mental ray is very fast. It also includes support for global illumination without having to enable the Advanced Lighting settings. In addition, mental ray can use all of Max’s existing materials without having to use a limited specialized material like the Raytrace material. Each material has a new rollout that lets you specialize mental ray settings.

mental ray also includes native support for Area Lights, Shaders, Depth of Field, and Motion Blur. It also includes some specialized lights that offer functionality, such as caustics, that is unavailable in the Scanline Renderer.

To choose mental ray as the renderer for your scene, simply select it from the list of available renderers in the Assign Renderer rollout of the Common panel of the Render Scene dialog box. You can set a different renderer for Production, the Material Editor, and the ActiveShade viewer. To make mental ray your default renderer, click the Save as Defaults button in this rollout.

Once selected as your Production renderer, you don’t need to modify any other settings for the renderer to work. The mental ray settings in the Material Editor, Lights category, and Object Properties dialog box enable additional features that mental ray can take advantage of, but they aren’t required to render the scene.

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mental ray preferences

In the Preference Settings dialog box is a panel of global mental ray settings, shown in Figure 44-12. In this panel, you can select to Enable mental ray Extensions. These extensions add some additional controls to several of the various mental ray panels.

Figure 44-12: The Preference Settings dialog box includes a panel of mental ray settings.

When the Scanline Renderer renders a scene, it progresses one line of pixels at a time down the image, but mental ray renders the image by breaking it up into blocks and rendering a block at a time. The Show Brackets on Current Buckets option displays white brackets around the current block as the image renders. You can also select to clear the frame before rendering.

The Messages section lets you specify which messages are displayed as the file renders. Options include Errors, Log Information, Log Progress, Debug Messages, and whether to write this information to a file.

Understanding Shaders

A Shader is an algorithm that defines how light is reflected through a scene. Surface Shaders determine the light properties that are reflected off the surface of an object; Atmospheric Shaders change the light properties as they move through a volume. Shaders can be programmed and applied to objects and scenes, and renderers like mental ray render the scene based on these shaders.

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mental ray materials and shaders

With the mental ray renderer selected, all materials include an additional rollout labeled mental ray Connection. This rollout, shown in Figure 44-13, is available only if the mental ray extensions are enabled in the mental ray panel of the Preference Settings dialog box. They

let you override the existing shaders used by the Scanline renderer and enable additional shaders that the mental ray renderer will use.

Figure 44-13: The mental ray Connection rollout in the Material Editor lets you override the default shaders.

The lock icons to the right of the shader buttons are the default shaders used by the Scanline renderer. To select a new shader, simply unlock these shaders by clicking the lock button.

If a material is opaque, you can speed up the rendering process by flagging the material as Opaque using the option at the bottom of the rollout.

If you want to get direct access to the shaders used by mental ray, use the mental ray material type, which presents all the shaders listed in the mental ray Connection rollout.

In addition to modifying the default materials to take advantage of mental ray, a number of mental ray materials and maps (shaders) are available from the Material/Map Browser, shown in Figure 44-14. These materials and maps show up only if the mental ray renderer is the assigned renderer and are marked in the Material/Map Browser with a yellow icon. All the mental ray materials and maps are split into different libraries, which are displayed in parentheses beside their name.

Note	Several materials and maps in the Material/Map Browser do not work with mental ray. These
	items are marked with a gray icon. You can hide all these items by disabling the
	Incompatible option in the Show section of the Material/Map Browser.

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Figure 44-14: The Material/Map Browser includes many additional mental ray materials and maps.

A complete list of the mental ray materials and maps is listed in Table 44-1.

	Table 44-1: mental ray Materials and Maps
Type	List
mental ray materials	DGS Material, Glass, mental ray
mental ray maps	3D Displacement, Beam, Bump, Combi, Contour Composite, Contour Contrast
	Function Levels, Contour Only, Contour PS, Contour Store Function, Curvature,
	Depth Fade, DGS Material, DGS Material Photon, Distortion, Edge, Edge
	Shadow, Environment, Façade, Factor Color, Glass, Glow, Landscape, Layer
	Thinner, Light Infinite, Light Point, Light Spot, Material to Shader, Metal, Mist,
	Night, Ocean, Opacity, Parti Volume, Parti Volume Photon, Photon Basic,
	Reflect, Refract, Shader List, Shadow Transparency, Simple, Stain, Submerge,
	Texture Remap, Texture Rotate, Texture Wave, Translucency, Transmat,
	Transmat Photon, Transparency, Two-Sided, UV Coordinate, UV Generator,
	Water Surface, Water Surface Shadow, Wet-Dry Mixer, Width from Color, Width
	From Light, Width form Light Direction, Wrap Around, XYZ Coordinate, XYZ
	Generator

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mental ray lights and shadows

If you look in the Lights category of the Create Lights Standard Lights menu, you see two mental ray specific lights: mental ray Area Omni and mental ray Area Point. These area lights spread light from a defined area in the Area Light Parameters rollout. By default, all mental lights use the Global Settings for their illumination values, but by using the mental ray Indirect Illumination rollout, shown in Figure 44-15, found in the Modify panel, you can override the global settings for the selected light.

Figure 44-15: The mental ray Indirect Illumination rollout lets you define the light settings for individual lights.

Enabling mental ray Shadow Maps

In the Shadows drop-down list is an option to enable mental ray Shadow Maps. These shadow maps are more accurate than normal shadow maps.

Understanding Caustics and Photons

Light properties for the mental ray renderer include four unique properties: Energy, Decay, Caustic Photons, and Global Illumination (GI) Photons. Before explaining these properties, you need to understand what caustics and photons are.

Caustics are those strange glowing lines that you see at the bottom of an indoor swimming pool caused by the light refracting through the water. Caustics are common in nature, and now with mental ray, you can add these effects to your scenes. Photons are small bundles of light energy, and like the raytracing rays, they are emitted from a light source with a given amount of energy. This energy is lost as the photon travels and as it hits objects in the scene.

The Energy value is the amount of light energy that each photon starts out with, and the Decay value specifies how quickly that energy dissipates. The number of Caustic and GI Photons determines the resulting accuracy of the lighting. More photons yield a better solution, but the greater number also increases the render time substantially.

Figure 44-16 shows a swimming pool with caustics glowing on the side of the wall. The left image shows the pool scene with caustics disabled, and the right image shows them enabled.

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Figure 44-16: This indoor swimming pool scene is rendered without caustics (left) and with caustics (right).

In order to get caustics to work in your scene, you need to add a Raytrace, Flat Mirror, or Reflect/Refract map to the Reflection map channel for the material that you want to generate caustics.

Enabling caustics and global illumination for objects

Another “gotcha” when dealing with caustics and global illumination is that each object can be specified to generate and/or receive caustics and global illumination. These settings are found in the mental ray panel of the Object Properties dialog box, shown in Figure 44-17. This dialog box can be opened using the Edit Properties menu command. If your scene isn’t generating caustics and you can’t figure out why, check this dialog box, because the Generate Caustics option is disabled by default.

	Figure 44-17: The Object Properties dialog
	box includes options for generating and
	receiving caustics and global illumination.
Tip	The Indirect Illumination panel of the Render Scene dialog box includes an option that can
	be used to cause All Objects to Generate and Receive Caustics and GI. Enabling this option
	enables these options for all objects regardless of their Object Properties settings.
	Controlling Indirect Illumination

In addition to the light settings, you can set many of the properties that control how caustics, global illumination, and final gather are computed in the Indirect Illumination panel of the Render Scene dialog box, shown in Figure 44-18.

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Figure 44-18: The Indirect Illumination panel includes settings for caustics, global illumination, and final gather.

For caustics and for global illumination, the Samples (or the Photons value for global illumination) value determines how the caustic photons are blended. A higher Sample value results in more blending and softer edges. The Radius value sets the size of each photon. This value is set automatically depending on the size of the scene. However, you can enable the Radius value and enter a new value manually.

The Volume setting is used by Volume material shaders to set the photon’s size. The Max Trace Depth settings determine the maximum number of reflections and refractions that a photon can take before it is ignored.

Photon maps can take a while to generate for a complicated scene, but once computed, they can be saved and reloaded. These files are saved using the .PMAP extension.

Final gather sends out rays to a scene that has computed caustics and global illumination already and computes the light at that location. All these rays are then combined to produce a total lighting picture of the scene and then blended to help fix any lighting abnormalities that may exist in the scene. The Samples value determines how many rays are cast into the scene. The final gather lighting pass can then be saved to a file after it is computed.

Rendering control

The core rendering settings for the mental ray renderer are contained within the Renderer panel of the Render Scene dialog box, shown in Figure 44-19. Using these settings, you can increase the speed of the renderer (at the expense of image quality).

The Sampling settings are used to apply an anti-aliasing pass to the rendered image. These samples can be filtered, and you can control the details of the contrast between the samples. The Bucket Width is the size of the blocks that are identified and rendered. Smaller buckets do not take as long to render and provide quicker feedback in the Render window.