3ds Max 2012 Bible - Kelly L. Murdock [496]
To create a disco ball effect using caustic photons, follow these steps:
1. Open the Disco ball.max file from the Chap 47 directory on the CD.
This file includes a simple room.
2. Open the Render Scene dialog box (F10), and switch the Production Renderer in the Assign Renderer rollout of the Common panel to the mental ray renderer.
3. Select Create⇒Standard Primitives⇒Sphere, and click in the Top viewport to create a sphere positioned toward the top of the room.
4. Press the M key to open the Slate Material Editor, double-click on the Standard material in the Material/Map Browser, and then double-click on the Raytrace map type in the Material/Map Browser. Then drag on the output socket for the Raytrace map and drop on the Reflection parameter. Then double-click the Standard material node to make its parameters appear, enable the Faceted option in the Shader Basic Parameters rollout; set the Opacity to 50, the Specular Level to 95, and the Glossiness to 30; and drag the standard material's output socket to the sphere object.
5. Select Create Lights⇒Standard Lights⇒mr Area Omni, and click in the Top viewport to create four lights that surround the sphere object. From the main menu, select the Tools⇒Light Lister option where you can quickly change the Multiplier value for each of the lights to 0.3. Then, using the Move tool, offset each light vertically from the others.
6. Select and right-click on each of the lights and open the Object Properties dialog box from the pop-up quadmenu. Open the mental ray panel in the Object Properties dialog box and enable the Generate Caustics option for each light.
7. Open the Render Scene dialog box (F10). In the Indirect Illumination panel, locate the Caustics section. Enable the Caustics option, set the Multiplier to 10, enable the Maximum Sampling Radius option, and set the Maximum Sampling Radius value to 1.0. At the bottom or the Caustics and Global Illumination (GI) rollout, enable the All Objects Generate and Receive GI & Caustics option. Then click the Render button.
Note
If the caustics aren't visible, make sure the Use Advanced Lighting option in the Render Setup dialog box is enabled. •
Figure 47.10 shows the resulting disco scene with thousands of lights visible on the walls.
FIGURE 47.10
This disco ball simply reflects the caustic photons around the room.
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 47.11. 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. There is also an option to exclude the object from caustics and from GI.
The mental ray panel in the Object Properties dialog box also includes settings so that you can configure how the object is treated during the Final Gather pass. Using the Return Black or Pass Through options, you can make the object unshaded or invisible to the final gather.
FIGURE 47.11
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 two rollouts of the Indirect Illumination panel of the Render Scene dialog box, shown