Talk:Radiosity (computer graphics)

message: * There's some bad grammar in the first part of this. The second paragraph in particular needs some work; it's not clear what it is saying. Osmaker 18:59, 20 October 2005 (UTC)
thread_title:  Comments 

message: The article at the very beginning references direct illumination algorithms and refers to ray tracing as an example of one. I however thought ray tracing was also a global illumination algorithm, and if you look at the wikipedia page on global illumination algorithms, it refers to ray tracing as an example of one. --Dterei 09:22, 17 October 2006 (UTC)
thread_title:  Global Illumination and Ray Tracing 

message: I have a replacement image that I think illustrates the difference between direct and global illumimation better than the ball image.
The image is from my own web site, and was generated using a radiosity renderer I wrote myself, therefore I own the copyright.
Eric Pierce, what do you think?  If nobody minds, I'll replace the image, and adjust the text accordingly. Rocketmagnet 18:10, 7 January 2007 (UTC)
thread_title:  replacing the ball picture 

message: Hi Trevor, Thanks for that, and the other changes. From what you wrote, I think it would be good to have a section, or sections, listing or detailing several algorithms (shooting, texture mapping, etc.)  If Agreed, I'll move your bit about shooting, and my bit about texturing into their own sections, which can then be expanded upon in a controlled manner by othe people.Rocketmagnet 09:43, 8 January 2007 (UTC)
thread_title: Different Algorithms

message: Sorry Trevor, I have reverted the caption for Radiosity_Progress.jpg. From "As additional bounces are calculated in shooting radiosity the scene becomes progressively brighter." back to "As the algorithm iterates, light can be seen to flow into the scene, as multiple bounces are computed."
This is because I believe the original caption to be the more correct one. This image was not rendered using shooting radiosity. It was rendered using texture mapping radiosity. Secondly, the image is not simply getting quantatively brighter. Rather a qualitative change is happening: light flowing through the scene.Rocketmagnet 09:43, 8 January 2007 (UTC)
thread_title: Caption for Radiosity_Progress.jpg

message: Trevor, I'm not sure why you deleted the line about radiosity being an iterative algorithm. The only other place I can see this mentioned is in the paragraph about shooting radiosity. I think that the fact that it's iterative is the highest level thing one can say about the working of the algorithm.Rocketmagnet 09:43, 8 January 2007 (UTC)
thread_title: Iterative Algorithm

message: Early methods used a hemicube (an imaginary cube centered upon the first surface to which the second surface was projected, devised by Cohen and Greenberg in 1985) to approximate the form factor, which also solved the intervening patch problem. This is quite computationally expensive, because ideally form factors must be derived for every possible pair of patches, leading to a quadratic increase in computation with added geometry.
I don't think this is correct in all cases. If each patch takes a constant time to render to the hemicube, then it's correct. Using the texture map method, then each 'surface' takes a constant time, and the number of patches makes practically no difference. Therefore it can be linear.
I think that it would be better to have a section detailing various methods. Rocketmagnet 12:38, 8 January 2007 (UTC)
thread_title: Quadratic Increase in Computation Time

message: Can anyone find a reference or paper stating that hard shadows are considered to be part of Global Illumination? Rocketmagnet 14:52, 9 January 2007 (UTC)
thread_title: Are shadows part of Global Illumination?

message: I'm not totally sure about this statement:
Likewise, Radiosity, by Hugo Elias describes a deterministic path tracing algorithm that takes advantage of graphics hardware to accelerate irradiance gathering, by using hemicubes. While this method does indeed compute the radiosity of patches, it does not compute form factors or explicitly construct a system of equations, thus it should not be confused with the classic radiosity method.
Do you have a reference for this?  Where do you get the definition of "classic radiosity"? Perhaps "full matrix" radiosity was the method described in the first paper on the technique, but the hemicube method is still considered radiosity. Surely a radiosity method would be any which computes the radiosity of patches. What the algorithm does then is up to it. Indeed, SIGGRAPH 1993 Education Slide Set: Radiosity Overview Page 2, by Stephen Spencer talks about both "full matrix" and "progressive" methods. and the next page talks about "Progressive Radiosity Variants". Therefore pointing to one implementation of radiosity and calling it something else seems odd. Unless a reference can be found, I'll revert this in a couple of days. Rocketmagnet 07:36, 10 May 2007 (UTC)
replies: text: Unfortunately, Rocketmagnet, I think the burden is on you to show that your method is radiometrically valid... that's how science works. ;) —The preceding unsigned comment was added by Trevorgoodchild (talk • contribs) 22:16, 10 May 2007 (UTC)
replies: text:  Can people please stop calling it my method? I'd love to take the credit for it, but basically I implemented radiosity from what I learned by reading articles and papers. As far as I can tell, it's one of the ways it's done. I believe it's discussed in the links above. The SIGGRAPH paper calls it radiosity. What more proof can I give that people call it radiosity? Rocketmagnet 23:58, 10 May 2007 (UTC)

text:  As for the burden of proof being on me, that the method I used is radiometrically valid, that's way out of my league, and doesn't interest either (should be obvious from the pictures that it works). The fact that other people (who use real equations on slides and everything) seem to say it is, is good enough for me. (Even Mr. 169.229.69.173 seemed to agree that it's radiometrically valid). Rocketmagnet 23:58, 10 May 2007 (UTC)
thread_title: What is "Real" Radiosity?

message: User:Ryulong has been reverting my edits on an attempt to move this page to Radiosity (computer graphics). In my view, radiosity (should that be capital R?) does not deserve to hold this page title. 
First and foremost this is a term borrowed from physics. The term that describes a fundamental phenomenon in physics with applications in engineering, optics, thermodynamics, and astronomy. In terms of the broad population or wikipedia users, it seems clear to me that this more fundamental meaning should precede the specialised use relating to this computer graphics algorithm. A disambiguation page is the correct approach.
Without the physical concept described by the physics term, there would *be* no computer algorithm. These are not two different meanings. The computer algorithm is an implementation of computation directional specular radiative transfer that borrows the name of one of the phenomena it models. It does not usurp the name.
My reference is the *very* popular (for mechanical engineers) undergraduate text Incropera and Dewitt, Fundamentals of Heat and Mass Transfer. The term 'radiosity is introduced in the first few pages of the radiation topic, as one of the foundation concepts of radiative transfer. Jdpipe 10:31, 11 June 2007 (UTC)
replies: text: I agree. "Radiosity" should be the physics article, and "Radiosity_(Graphics)" should be this one. How do we go about getting it changed? Rocketmagnet 14:14, 11 June 2007 (UTC)
replies: text:  Hi Rocketmagnet. I see that you are one of the key authors of this page -- and a good page it is too. Your agreement will be a help on this. There is currently a block on moving the page but after 18 Jun we can progress it, providing there are no objections raised here. Perhaps you will be able to help with filling out that page (Radiosity (heat transfer)). Specifically, mechanical engineer use a matrix-based radiosity calculation to estiamte temperatures of surfaces in a grey-body radiative transfer situation. Thought it might be good to put that on that page, and I imagine there would be some good parallels with your stuff here. Cheers, Jdpipe 11:55, 14 June 2007 (UTC)
thread_title:  Radiosity is first and foremost a physics term 

message: I think you missed one important thing: calculation results are viewpoint-independend.  —Preceding unsigned comment added by 83.25.52.170 (talk) 19:08, 27 February 2008 (UTC)
thread_title:  Re: Advantages