bidirectional path tracing и ускорения

на основе https://github.com/githole/edubpt можно потестировать некоторые ускорения для bidirectional path tracing:

• Probabilistic Connections for Bidirectional Path Tracing
  http://www.researchgate.net/figure/280603062_fig2_Figure-1-Our-Probabilistic-Connections-for-Bidirectional-Path-Tracing-approach
• Reducing the number of shadow rays in bidirectional path tracing
  http://graphics.cs.kuleuven.be/publications/RTNOSRIBPT/
  
• Robust Adaptive Photon Tracing using Photon Path Visibility
  http://cs.au.dk/~toshiya/amcmcppm.pdf
• A Path Space Extension for Robust Light Transport Simulation
  http://cs.au.dk/~toshiya/ups_tr.pdf