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Using Local Advanced Lighting Settings

You can set advanced lighting settings locally for specific objects using the Object Properties dialog box, as shown in Figure 28-6.

At the top of the panel is the number of selected objects and lights. This dialog box lets you specify whether this object should be excluded from the advanced lighting calculations. The properties can be set By Object or By Layer. If included, you can select whether the object casts shadows, receives illumination, and how it handles Radiosity. The Number Regathering Rays Multiplier option sets the number of rays cast by the selected object. For large smooth surfaces, reducing artifacts by increasing this value can be helpful. The rest of the settings in this panel deal with Radiosity.

Figure 28-6: Use the Advanced Lighting panel in the Object Properties dialog box to disable advanced lighting.

Tutorial: Excluding objects from light tracing

Using the Object Properties dialog box, you can exclude certain objects from the light tracing calculations.

To exclude objects from the Light Tracer, follow these steps:

1.Open the Heated hotplate.max file from the Chap 28 directory on the CD-ROM. This file includes a simple model of a hotplate.

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2.Open the Advanced Lighting panel by selecting Rendering Advanced Lighting Light Tracer (or press the 9 key). In the Parameters rollout, set the Bounces value to 2.

3.In the Front viewport, select the plug, cord, and floor objects, and then select Edit Object Properties to open the Properties dialog box for these objects. In the Object Properties dialog box, open the Advanced Lighting panel and enable the Exclude from Advanced Lighting Calculations option.

4.In the Render Scene dialog box, click the Render button. This renders the scene in the Rendered Frame Window.

Figure 28-7 shows the scene rendered with advanced lighting that excludes certain objects.

Figure 28-7: Color bleeding becomes much stronger with a higher

Bounce value.

Working with the Advanced Lighting

Override Material

Applying an advanced lighting solution can have a direct impact on the materials in the scene. The Material Editor includes a material that is useful for working with advanced lighting: the Advanced Lighting Override material.

Note The Advanced Lighting Override material does not need to be applied to all objects that are to receive advanced lighting. It is used only to override the existing scene settings for certain materials.

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As an example of how this material can be used, consider the last example. Rather than excluding objects from the Advanced Lighting calculations, you can instead use the Light Tracer panel to set the global settings for the scene and apply the Advanced Lighting Override material to the hotplate coils with a higher Color Bleed value. This causes the coils to bleed, but not the rest of the scene.

Another common use for this material is to use the Luminance Scale value to cause selfilluminating materials to add light energy to the global illumination calculations.

The Advanced Lighting Override material type includes material parameters that override the Advanced Lighting solution. These parameters, shown in Figure 28-8, let you set the amount of Reflectance, Color Bleed, Transmittance, Luminance, and Indirect Light Bump Scale that the material uses.

Figure 28-8: The Advanced Lighting Override Material rollout defines how light interacts with the material.

Summary

Advanced lighting offers a new way to shine lights on your scenes. With these features, many new lighting options are available. Advanced lighting enables two global illumination methods: light tracing and radiosity. In this chapter, light tracing was the focus. This chapter covered the following topics:

Enabling advanced lighting

Discovering light tracing

Setting local advanced lighting settings

Using the Advanced Lighting Override material

In the next chapter, you dig deeper into advanced lighting by looking at radiosity.

Advanced Lighting

and Radiosity

If you thought that advanced lighting was covered already, then you’d be missing half the boat. Radiosity is a lighting solution that

is used to compute lighting solutions that are much more realistic than the standard lighting solution. The solution deals with the effect of light bouncing off objects and being reflected to the environment. As you start to learn and use Radiosity, you’ll quickly discover that it is a complex system that takes lots of tweaking to get just right.

Understanding Radiosity

Imagine a scene that includes an umbrella with a light source directly overhead. If you rendered the scene, the object caught in the umbrella’s shadow would be too dark to see clearly. To fix this situation, you would need to add some extra lights under the umbrella and set them to not cast shadows. Although this workaround provides the solution we want, it is interesting to note that in real-life, this isn’t the case.

The difference between the workaround and real life has to do with the effect of light energy being reflected (or bounced) off the lit objects. It is this phenomenon that allows me to look down the hall and see whether my children’s light is still on past bedtime. Even though I can’t see the light directly, I know it is on because of the light that reflects off the other walls.

Radiosity is a lighting algorithm that follows rays of light throughout the scene, and every time it strikes a surface, the light energy is reduced, but the light energy is bounced onto the surrounding faces. The number of bounces that are computed, the more realistic the lighting solution, but the longer it takes to compute. So, using radiosity, the objects under the umbrella are visible even if they are in the shadows.

Radiosity is mostly used to light indoor scenes because that is where the effect of light bouncing is most evident. Radiosity, along with light tracing, is another method for computing global illumination. Figure 29-1 shows the dinosaur exhibit in a museum with and without radiosity. Notice how dark the shadows are in the normal lighting image.

29C H A P T E R

In This Chapter

Using advanced lighting

Understanding radiosity

Setting global advanced lighting parameters

Using the Lightscape material

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Figure 29-1: This scene is lighted using normal lighting (left) and radiosity lighting (right).

Lighting for Radiosity

The Advanced Lighting panel in Max includes light tracing and radiosity options. You can select either from the Advanced Lighting panel in the Render Scene dialog box. You can open this panel with the Radiosity option selected using the Rendering Advanced Lighting Radiosity menu command. Pressing the 9 key opens the Render Scene dialog box with the Advanced Lighting panel open.

Cross-	Light tracing is covered in Chapter 28, “Advanced Lighting and Light Tracing.”
Reference

Radiosity lighting is not displayed until you have Max compute it by clicking the Start button in the Radiosity Processing Parameters rollout. After a radiosity solution is calculated, the results are saved as light maps. These maps are easy to apply to a scene and can be viewed within the viewports. However, when the geometry or lights of the scene change, you need to recalculate the lighting solution.

The Radiosity Processing Parameters rollout, shown in Figure 29-2, lets you set the quality of the radiosity solution. You can also specify the number of iterations to use for the scene and for the selected objects. These are different steps in the radiosity computation. The Initial Quality defines how accurate the rays that are bounced around the scene are. This stage sets the brightness for the scene. The Refine Iterations improves the general quality of the lighting solution for each iteration. You can refine iterations only for the selected object. This lets you target the iterations instead of computing them for the entire scene.

The Interactive Tools section lets you specify a Filtering value. A greater Filtering value eliminates noise between adjacent surfaces by averaging the lighting coming from all surrounding surfaces. The Setup button offers access to the Exposure Control rollout in the Environment panel. You can also turn off Radiosity in the viewports.

Cross-	Chapter 41, “Rendering Basics,” includes coverage of the Exposure Control rollout.
Reference

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Figure 29-2: The Radiosity Processing Parameters rollout includes buttons for computing a solution.

	Subdividing a mesh for radiosity
	As you begin to play with radiosity, you’ll quickly find that to get accurate results, you
	need to have good, clean models. If any models have long, thin faces, then the results are
	unpredictable.
	The Radiosity Meshing Parameters rollout includes an option to enable meshing and a
	Meshing Size value. This setting is the same as the Size value parameter for the Subdivide
	modifier, except that it is applied globally.
Tip	If you’re creating an indoor room using the Box object, be aware that Box objects have only
	one external face surface with normals, so the interior of a Box object will not have the cor-
	rect lighting. You can easily fix this by applying the Shell modifier to the Box object. This adds
	an interior set of faces to the Box object.

Using the Subdivide modifier

The Modifiers menu includes a submenu for Radiosity modifiers. This submenu includes only the Subdivide modifier and a World-Space version of the Subdivide modifier. This modifier accomplishes a simple task — to create a mesh that has regular, equally shaped triangular faces that work well when computing a radiosity solution.

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Tip

Tip

Although this modifier was created to help with radiosity solutions, it also helps with other commands that require regular mesh faces such as the Boolean and Terrain compound objects.

The Parameters rollout includes a Size value that determines the density of the mesh. The lower the value, the denser the mesh and the better the resulting radiosity solution, but the longer the solution takes. This same Subdivision Size setting can also be found (and set globally) in the Radiosity Meshing Parameters rollout of the Advanced Lighting panel. It is also found in the Advanced Lighting panel of the Object Properties dialog box. Figure 29-3 shows a simple cube with the Subdivide modifier applied and the Size value set to (from left to right) 50, 30, 25, 20, and 12.

If you drag the Size value, you’ll probably want to set the Update option to Manual or you’ll find yourself waiting while Max computes some seriously dense mesh, or you can just disable the Display Subdivision option.

Figure 29-3: The Subdivide modifier changes all mesh faces into regularly shaped triangular faces.

Tutorial: Preparing a mesh for radiosity

When it comes to meshes that have long, thin, and irregular faces, you don’t have to look any further than Boolean compound objects. These objects typically are divided along strange angles producing ugly meshes. The good news is that these meshes are easy to subdivide.

To subdivide an irregular mesh in preparation for a radiosity solution, follow these steps:

1.Open the Boolean object.max file from the Chap 29 directory on the CD-ROM.

This file includes two copies of a Box object with an arch shape Boolean subtracted from it.

2.Select the top object, and choose the Modifiers Radiosity Modifiers Subdivide menu command.

This applies the Subdivide modifier to the object.

3.In the Parameters rollout, select the Manual update option, set the Size value to 5.0, and click Update Now.

If the Display Subdivision option is enabled, then the changes are visible in the viewport.

4.Open the Advanced Lighting panel with the Rendering Advanced Lighting menu command (or press the 9 key). Select Radiosity from the drop-down menu.

Figure 29-4 shows the two objects with and without the Subdivide modifier applied. The top object is ready for a radiosity solution.

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Figure 29-4: Subdividing an irregular mesh prepares it for radiosity lighting.

Painting with light

The Light Painting rollout (found in the Advanced Lighting panel of the Render Scene dialog box), shown in Figure 29-5, includes buttons for Adding Illumination, Subtracting Illumination, and Picking an Illumination value from the scene. Using these tools, you can paint lighting on the objects in the scene. The Clear button removes all the changes you’ve made using the Light Painting tool.

Figure 29-5: Because lighting is saved as a light map, you can add or subtract light from the scene using a brush tool.

Rendering parameters and statistics

Settings in the Rendering Parameters rollout (shown in Figure 29-6) are used during the rendering process. The Re-Use and Use Direct Illumination options give you the chance to re-use the existing radiosity solution when rendering or to recalculate it as part of the rendering process. This can save some time during rendering.

The Regather Indirect Illumination option enables a Light-Tracer-like step along with the radiosity solution and produces an image that has the best of both solutions. The regathering options are the same as those defined for the light tracer.

The Statistics rollout includes information about the Radiosity process. Using this information, you can judge whether the settings are too high or too low.

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Figure 29-6: The Rendering Parameters and Statistics rollouts offer rendering options and statistics for radiosity solutions.

Tutorial: Lighting an archway with radiosity

Radiosity works best in indoor scenes or scenes that are mostly interior, so I’ve created a simple walkway with several archways. The only light source for this scene is an IES Sun light streaming in from the left.

To light an archway with Radiosity, follow these steps:

1.Open the Arch walkway.max file from the Chap 29 directory on the CD-ROM. This file includes a simple walkway made from primitives.

2.Open the Advanced Lighting panel with the Rendering Advanced Lighting menu command (or press the 9 key). Select Radiosity from the drop-down list in the Select Advanced Lighting rollout.

3.In the Radiosity Processing Parameters rollout, set the Refine Iterations value to 2 and click the Start button to have Max compute the radiosity solution.

4.In the Rendering Parameters rollout, enable the Render Direct Illumination, the Regather Indirect Illumination, and the Adaptive Sampling options.

Figure 29-7 shows the finished rendered walkway. Notice that all surfaces are well lit even though the scene has only a single light.