Sampling Settings #

The sampling settings control the Monte Carlo based ray tracing algorithm and decides how many rays should be cast and when they should be terminated. Rays can either be terminated by reaching the maximum depth or by the Russian Roulette mechanism which terminates rays using a probability based on ray path throughput.

Samples#

The samples specify the side length of the grid within which randomly sampled rays that are cast. Meaning that the total number of rays is the square of the samples. For example, 100 samples will result in 10,000 rays being cast.

Max Depth#

The absolute max amount of bounces that a ray path can do before it is terminated. For example, a value of 0 for this parameter will allow direct contribution only, while a value of 4 will permit up to 4 bounces of global contribution.

Roulette Depth#

The path depth at which to begin Russian Roulette termination. Russian Roulette may terminate ray paths after this depth, especially if they contribute little to the result.

Roulette Threshold#

The path throughput threshold below which to perform Russian Roulette. Russian Roulette may terminate ray paths if their throughput is below this value.

Info

Russian Roulette improves the efficiency of the Monet Carlo estimation by terminating ray paths that have a low contribution to the final result. It can significantly reduce calculation times while still computing the correct value on average.

In order for a ray to be considered for Russian Roulette termination it must have a path depth greater or equal to the Roulette Depth and a throughput lower than the Roulette Threshold.

Preset Settings#

There are preset settings that can be used instead of specifying each individual parameter. These are tuned to provide the represented quality while using minimal amount of computational resources.

Warning

Scene complexity can greatly affect the settings required to reduce noise and converge to a stable result. These presets are a general guidance and may not be suitable for all scenes.

Analysis Quality#

The analysis presets are tuned for analysis purposes where samples are taken in a hemispherical grid around an analysis point.

Analysis Quality	Samples	Max Depth	Roulette Threshold
Low	50 (2,500)	4	4e-6
Medium	100 (10,000)	6	1e-6
High	200 (40,000)	8	2.5e-7
Ultra	600 (360,000)	12	2.77e-8

Render Quality#

The render presets are tuned for visualization purposes where samples are taken within a pixel.

Render Quality	Samples	Max Depth	Roulette Threshold
Low	4 (16)	2	0.2
Medium	8 (64)	4	0.01
High	16 (256)	8	0.004
Ultra	32 (1024)	12	0.001