Autodesk 12812-051462-9011 User Guide 3 - Page 1056

TIP To preview global illumination, set Samples to 100, then increase the value for a final rendering. Maximum Sampling Radius When on, the numeric value sets the size of photons. When off, each photon is calculated to be 1/10 of the radius of the full scene. Default=off, 1.0. In many cases, the default photon size (Maximum Sampling 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. When photons overlap, the mental ray renderer uses sampling to smooth them together. Increasing the number of samples increases the amount of smoothing and can create more natural-looking caustics. When photons have a small radius and don't overlap, the Samples setting has no effect. For global illumination, photons should overlap. To get good results, you might need to turn on Maximum Sampling Radius and increase the photon size. Merge Nearby Photons (saves memory) Enables reduction of the memory footprint of the photon map. When on, use the numeric field to specify the distance threshold below which mental ray merges photons. The result is a smoother, less-detailed photon map that uses significantly less memory. Default=off, 0.0. NOTE Loading a legacy file uses the default value of 0.0. Also, using a value of 0.0 is equivalent to turning the feature off. Optimize for Final Gather (Slower GI) If turned on before you render the scene, the mental ray renderer computes information to speed up the regathering process. Specifically, each photon stores additional information about how bright its neighbors are. This is particularly useful when combining Final Gather with Global Illumination, in which case the additional information allows Final Gather to quickly determine how many photons exist in a region. The fast lookup computation can take a long time, but it can greatly reduce the total rendering time. Default=off. The fast lookup computation can be can be stored as additional data inside a photon map file on page 8093, and then reused in subsequent renderings. Volumes group The controls in this group and the ones that follow are for the photon maps on page 8090 used to calculate caustics and global illumination. This group controls volumetric caustics. Volumetric caustics require a material to have a volume shader assign to its Photon Volume component. mental ray Renderer | 6311