@InProceedings{	  schjoth.frisvad.erleben.sporring.07,
  author	= {Lars Schj{\o}th and Jeppe R. Frisvad and Kenny Erleben and
		  Jon Sporring},
  title		= {Photon Differentials},
  year		= {2007},
  month		= {dec},
  keywords	= {Ray tracing, global illumination, photon mapping,
		  caustics, ray differentials},
  booktitle	= {Proceedings of {GRAPHITE} 2007},
  abstract	= {A number of popular global illumination algorithms use
		  density estimation to approximate indirect illumination.
		  The density estimate is performed on finite points -
		  particles - generated by a stochastic sampling of the
		  scene. In the course of the sampling, particles,
		  representing light, are stochastically emitted from the
		  light sources and reflected around the scene. The sampling
		  induces noise, which in turn is handled by the density
		  estimate during the illumination reconstruction.
		  Unfortunately, this noise reduction imposes a systematic
		  error (bias), which is seen as a blurring of prominent
		  illumination features. This is often not desirable as these
		  may lose clarity or vanish altogether. We present an
		  accurate method for reconstruction of indirect illumination
		  with photon mapping. Instead of reconstructing illumination
		  using classic density estimation on finite points, we use
		  the correlation of light footprints, created by using Ray
		  Differentials during the light pass. This procedure gives a
		  high illumination accuracy, improving the trade-off between
		  bias and variance considerable as compared to traditional
		  particle tracing algorithms. In this way we preserve
		  structures in indirect illumination.}
}

@InCollection{	  schjoth.olsen.ea:07,
  author	= {Lars Schj{\o}th and Ole Fogh Olsen and Jon Sporring},
  title		= {Diffusion Based Photon Mapping},
  booktitle	= {Advances in Computer Graphics and Computer Vision},
  pages		= {109--122},
  publisher	= {Springer},
  year		= {2007},
  series	= {Communications in Computer and Information Science},
  editor	= {Jos\'{e} Braz and Alpesh Ranchordas and Helder Ara\'{u}jo
		  and Joaquim Jorge},
  volume	= {4},
  note		= {Revised and Selected Papers from VISAPP and GRAPP 2006}
}

@InProceedings{	  schjoth.olsen.ea:06,
  author	= {Lars Schj{\o}th and Ole Fogh Olsen and Jon Sporring},
  title		= {Diffusion Based Photon Mapping},
  booktitle	= {First International conference on Computer Graphics --
		  Theory and Applications -- {GRAPP} 2006},
  editors	= {Jos\'{e} Braz and Joaquim Jorge and Miguel Dias and
		  Ad\'{e}ritos Marcos},
  year		= {2006},
  address	= {Set\'{u}bal, Portugal},
  month		= feb # {~25--28},
  pages		= {168--175}
}