Random-pattern pixel sampling in raytracing instead of uniform grids — cuts aliasing and noise through intelligent distribution. Industry standard for contemporary 3D work.
In ray tracing, rays are cast through pixels to calculate the scene. Regular grids — one ray per pixel, or 4x4, or 16x16 in a line — create visible patterns and aliasing, especially on fine edges and highlights. Stochastic Sampling breaks up this structure: the sample points are distributed pseudo-randomly, not arranged in a Cartesian grid. The eye perceives randomness as noise — and noise is less disturbing to our brain than geometric artifacts.
The practice: You define a sampling rate (e.g., 64 or 256 samples per pixel) and distribute them over the pixel area not in grids, but according to Poisson disk patterns, Halton sequences, or simply jittered random. At the same time, the same principle is used for Importance Sampling — rays are concentrated in directions that actually bring light (e.g., directly to the light source instead of in all directions). This massively reduces the sampling count for acceptable noise. In Monte Carlo rendering (path tracing, bidirectional tracing), stochastic sampling is not optional — it is the method itself.
You don't feel this directly on set, but in the VFX pipeline: the compositor or render farm supervisor chooses the sampling pattern. Low-noise sequences (Sobol, Scrambled Sobol) converge faster, requiring fewer samples for the same visual result. This saves render time. Classic random noise — white noise — often requires double or triple the sample count. Adaptive Sampling (more samples in noisy areas) combines stochastic sampling with intelligent mask generation.
A direct production effect: You see the differences in greenscreen compositing or with motion blur effects (see also Motion Blur, Depth of Field). Old, grid-based renderers showed hard, flickering edges in animation. Stochastic sampling turns this into controlled grain — which is more stable and can be filtered better in post without losing detail. Modern rendering (Arnold, RenderMan, V-Ray) uses Sobol sampling by default. It's no longer a question of *whether* to use stochastic sampling, but which sequence and how many samples per pixel.