Path Sampling Techniques for Efficient Light Transport Simulation

Iliyan Georgiev
PhD thesis, Saarland University, 2015

Our importance caching method for many-light rendering (left) quickly finds the few most relevant virtual point lights (VPLs) for each pixel by using VPL importance distributions constructed for a small subset of all pixels. By adaptively combining light transport estimators from bidirectional path tracing and photon mapping, our vertex connection and merging algorithm (middle) can efficiently render scenes with a wide range of lighting effects. Our joint path sampling approach (right) constructs light transport paths by prescribing the joint distribution of sequences of vertices in participating media, improving rendering efficiency by orders of magnitude over prior path sampling techniques.


Reproducing the interactions between light and matter in a physically accurate way can significantly improve the realistic appearance of synthetic images, however such effects can be very computationally expensive to simulate. Pressed by strict requirements on image quality and visual realism, industrial applications have recently moved away from using legacy rasterization-based rendering solutions to fully embrace physically-based Monte Carlo methods. This dramatic shift has rekindled the interest in developing new and robust light transport simulation algorithms that can efficiently handle a wide range of scenes with complex materials and lighting – a problem that we address in this thesis.

State-of-the-art Monte Carlo methods solve the global illumination problem by sampling random light transport paths in the scene via ray tracing. We analyze the efficiency of these methods, devise new path sampling techniques for rendering surface and volumetric light scattering, and develop novel means of leveraging illumination coherence via path reuse. This results in several practical rendering algorithms that produce images with less noise and remain more resilient to variations in the scene configuration than existing methods. The improved efficiency of these algorithms comes from the use of new and diverse sampling techniques, each specialized for handling a different set of lighting effects. Their robustness is due to the adaptive combination of these techniques in a way that preserves their individual strengths.

Downloads and links

BibTeX reference

  title   = {Path Sampling Techniques for Efficient Light Transport Simulation},
  author  = {Georgiev, Iliyan},
  school  = {Saarland University},
  address = {Saarbr{\"u}cken, Germany},
  Year    = {2015}