Talk:Photon mapping

message: The article says that reverse ray tracing originates the light rays at the light source. But doesn't reverse ray tracing have the rays start at the camera? MichaelGensheimer 21:26, 15 Nov 2003 (UTC)
thread_title:  reverse ray tracing? 

message: You write "... to decrease the energy of the photon ...". I suppose this does not refer to the engery of a photon in a physical sense. Since the energy of a photon is related to its frequency by E = hf, changing the energy will change its frequency. On the other hand, the frequency distribution of light determines its color.
--Borishollas (talk) 17:23, 8 December 2007 (UTC)
thread_title:  Photon energy 

message: I organized the article, as the original one had information about various parts of the photon mapping method scattered about.  I also corrected some incorrect information (including my own), that originated from the belief that radiance estimates came from photon density or irradiance estimates.  I expounded on the common effects that photon mapping is used for as well.  Also, I noticed that some information about different implementations of photon mapping was included before (or in replacement of) the actual method, so I moved these to the "Variations" section.  I also added information about how exactly radiance was construed from a photon map, which was not present before.  I hope my edits clarify and make this article seem cleaner.  Comments? Xcelerate (talk) 04:49, 8 March 2008 (UTC)
thread_title:  Re-did article 

message: In the article, it is said that the bias comes from the fact that if you average infinitely many renderings, you don't get the correct solution. Although I agree with the fact itself, I am wondering why this is taken as the definition of bias, and not as "if you take an infinite number of photons" which would make more sense imho. In a statistical sense, the estimated illumination at any given pixel is not different from the expected one if you take an infinite number of photons, thus not creating any bias, ie., the expected value equal the empirical mean..over photons. Isn't it ?
Nbonneel (talk) 16:46, 27 August 2009 (UTC)
thread_title:  bias 

message: The article reads:
:In the 1st pass of photon mapping, an alternative to using Russian roulette to determine direction is to give each photon an "energy" attribute. Each time the photon collides with an object, this attribute is also stored in the photon map. The energy is subsequently then lowered. Once the energy of the photon is below a certain pre-determined threshold, the photon stops reflecting.
Is there literature behind this idea? It doesn't seem like a good idea to me, mainly because it breaks PM's consistency -- objects which are several reflections away from a light source will be under-illuminated. Some PM implementations will insert several entries in the PM as a photon's path is traced, but they still use RR to maintain consistency. Thoughts? — xDanielx T/C\R 09:54, 22 November 2010 (UTC)
thread_title:  Russian roulette alternative 

message: It says in the article that the intersection point and incoming direction are stored in the photon map, but isn't the wavelength (the color) of the photon stored here too? —Kri (talk) 23:12, 15 July 2011 (UTC)
thread_title:  What about wavelength?