Graphics Reference
In-Depth Information
Radiosity
Lighting with
radiosity
(or global illumination) adds a significant amount of photorealism to a 3D scene.
Radiosity takes into account light from indirect sources (such as the environment), light bouncing/bleeding,
and light from luminous textures. There are a number of ways to light a scene when using global illumina-
tion. Scenes can be lit with traditional CG lights as main lights and allow bounce lighting to create second-
ary illumination. Lighting can come from simple environments such as gradients or even from image-based
light files using high dynamic range (HDR) images. Lighting can even be produced by increasing the Lu-
minous Intensity on textures for objects that would cast light in the real world (TVs, computer screens, and
so forth). Most realistic scenes take advantage of this type of rendering to produce accurate and natural light.
Doing the following enables global illumination: On the Shader Tree tab, click the Render item. Click the
Properties tab, and then click the Global Illumination section on the right side. Under Indirect Illumination,
select the Enable option. After Indirect Illumination is enabled, the default settings for Global Illumination
will provide you with a decent radiosity solution. Next, you will take a look at several samples that utilize
different methods of lighting using radiosity.
Traditional Lights and Radiosity
First, you will look at a scene that uses a Directional Light set to Physical Sun and multibounce global illu-
mination to fill out the lighting. The Indirect Illumination properties allow you to set the number of bounces
the light ray can take to illuminate the scene. With Indirect Illumination enabled, the default is one bounce,
but this can be increased to achieve more-accurate lighting. Take into account the increased calculations re-
quired as the number of bounces increases, because higher numbers will adversely affect render time. Typ-
ically, the setting of two or three bounces is all that is needed to produce the desired lighting effects. In the
