2011

Table Of Contents
Photons and Sampling Radius
The intensity of global illumination is computed by the number of photons
youve specified. Increased numbers of photons makes global illumination
less noisy but also more blurry. When the number of photons are decreased,
global illumination is more noisy but less blurry. The greater the number of
photons, the longer the rendering time.
TIP To preview global illumination, give settings such as Photons/Sample or
Photons/Light lower values, then increase the values for the final rendering.
The sampling radius sets the size of photons. In many cases, the default photon
size (Use Radius=Off) of one-tenth the scene size gives useful results. In other
cases, the default photon size might be too large or too small.
The size of the sampling radius (Radius) determines if photons overlap. When
photons overlap, the renderer smooths them together. Increasing the radius
increases the amount of smoothing and can create more natural-looking
illumination. When photons have a small radius and don't overlap, no
smoothing occurs. Ideally, photons should overlap. To get good results, you
would want to turn on Use Radius and increase the Radius size.
Global Illumination Trace Depth
The Trace Depth controls are similar to those for calculating reflections and
refractions, but they refer to the photons used by global illumination rather
than to light rays used in ray-traced reflection and refraction.
The maximum depth limits the combination of reflection and refraction.
Reflection and refraction of a photon stops when the total number of both
equals the maximum depth. For example, if Max Depth equals 3 and Max
Reflections and Max Refractions are both set to 2, a photon can be reflected
Benefits of Indirect Illumination | 2137