UImportanceSamplingLibrary

class Engine Blueprint Since 5.0

Inherits: UObjectBase › UObjectBaseUtility › UObject › UBlueprintFunctionLibrary › UImportanceSamplingLibrary

#include "Kismet/ImportanceSamplingLibrary.h"

Description

Blueprint function library for quasi-random (Sobol sequence) sampling and texture-driven importance sampling, used to distribute sample points non-uniformly according to a probability weighting such as texture luminance.

Caveats & Gotchas

• The Sobol functions produce low-discrepancy quasi-random sequences, not uniform pseudo-random numbers — they're designed to fill space evenly across many samples rather than to look statistically random for a single draw.
• MakeImportanceTexture / ImportanceSample are built for CPU-side sampling (e.g. placing lights or particles from a texture) and are relatively expensive; they are not meant to run per-frame on large textures without caching the FImportanceTexture.

Functions (9)

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Access	Type	Name	Description
public	function	UImportanceSamplingLibrary::BreakImportanceTexture	Extracts the original source texture and weighting function that were used to build an FImportanceTexture.
public	function	UImportanceSamplingLibrary::ImportanceSample	Draws a single importance-weighted sample position from a precomputed FImportanceTexture, biasing toward brighter (or otherwise higher-weighted) regions of the source texture.
public	function	UImportanceSamplingLibrary::MakeImportanceTexture	Builds an FImportanceTexture from a 2D texture, precomputing cumulative distribution functions per row and per pixel so ImportanceSample can later draw points proportional to the chosen weighting channel.
public	function	UImportanceSamplingLibrary::NextSobolCell2D	Advances a 2D Sobol cell sequence to the next point using the previous sample, avoiding recomputation from index 0.
public	function	UImportanceSamplingLibrary::NextSobolCell3D	Advances a 3D Sobol cell sequence to the next point using the previous sample, avoiding recomputation from index 0.
public	function	UImportanceSamplingLibrary::NextSobolFloat	Advances a Sobol sequence to the next sample using the previous sample's value, avoiding the cost of recomputing the whole sequence from index 0.
public	function	UImportanceSamplingLibrary::RandomSobolCell2D	Returns a Sobol-distributed 2D position within a specific cell of a stratified grid, useful for jittered/stratified sampling patterns like Poisson-disk-style scattering.
public	function	UImportanceSamplingLibrary::RandomSobolCell3D	Returns a Sobol-distributed 3D point within a specific cell of a stratified 3D grid, for volumetric jittered sampling patterns.
public	function	UImportanceSamplingLibrary::RandomSobolFloat	Returns a Sobol-distributed quasi-random number between 0 and 1 for the given sample index and dimension.

Version History

Introduced in: 5.0

Version	Status	Notes
5.6	stable	—

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