Talk:Caustic (optics)

Review
This page could use a review by someone who knows more about this than I do.--Srleffler 02:51, 3 March 2006 (UTC)

New image
I'm not sure about that new image. It's very nice, but Profanity seems to say that images that may be objectionable should be used "if and only if their omission would cause the article to be less informative, relevant, or accurate, and no equally suitable alternatives are available." While the image is clearly relevant in that it shows optical caustics, I'm not sure one can argue that its omission would weaken the article, or that no equally suitable images of caustics are available (there being such an image on the article already). Wikipedia is not censored, but that doesn't mean that everything is always appropriate and encyclopedic. --Srleffler 19:33, 23 July 2006 (UTC)

Gone. HighInBC 21:21, 23 July 2006 (UTC)


 * This piqued my curiosity - the image seems to have been a candid topless shot of a woman on a Mexican beach that was spammed to several articles (including sepia). It's been deleted and part of me wonders if the man who took the shot eventually went to prison. It was added to the article by User:H, who is actually User:HighInBC (above); he almost immediately removed it. It appears that User:HighInBC was also an admin, and left Wikipedia a year later after a perception that there had been threats to his family. I wonder which username he uses now? -Ashley Pomeroy (talk) 17:19, 25 April 2014 (UTC)


 * If I recall correctly, the image was of a topless woman floating in water, with caustics visible in the water. I don't know anything about the dispute that caused H to leave. As an admin, he was in contact with (and sometimes in dispute with) many other editors, and I don't see any one that stands out as being likely related to the threats.--Srleffler (talk) 04:01, 26 April 2014 (UTC)

Name
Such concentration of light, especially sunlight, can burn—hence the name. Something about the ethymology? --Abdull 12:27, 5 August 2006 (UTC)
 * Yes. The word caustic comes from Greek καυστός, burnt, via the Latin causticus, burning. The article presumes readers are at least familiar with the much more common use of the term caustic to refer to aggressive chemicals like acids that can "burn" exposed skin.--Srleffler 16:57, 5 August 2006 (UTC)

Cardiod or Nephroid?
Wolfram says "The cardioid is a degenerate case of the limaçon. It is also a 1-cusped epicycloid (with r==r) and is the catacaustic  formed by rays originating at a point on the circumference of a circle and reflected by the circle." But User:Pne changed it to Nephroid. Which is correct? Both, depending on where the light comes from? Dicklyon 17:43, 16 September 2006 (UTC)
 * Collett's book claims the locus is a cardioid. Of course it wouldn't be the first error I've found in that book. (Reference on my user page.) Nevertheless, if Pne feels this is correct, he/she needs to provide a reference. Otherwise, it's original research.--Srleffler 03:31, 17 September 2006 (UTC)


 * The operative bit in the quote you gave is 'rays originating at a point on the circumference of a circle'. Parallel rays instead produce a nephroid; rays from a source in between infinity and the circumference of the circle produce something in between a cardioid and a nephroid. So, by my understanding, the answer to your question 'Both, depending on where the light comes from?' is 'Yes'. See this Mathworld page, for example. -- pne (talk) 18:42, 18 September 2006 (UTC)

Comments to mbz1 regarding images
I reverted your original replacement of two images yesterday (but not their re-addition today). As I said in my edit summary, I reverted because the images you removed both illustrated specific points discussed in the text—the first shows a caustic with a nephroid shape, which is important in the theory of caustics and is of some mathematical interest. The second image illustrates the simulation of caustics in computer graphics. The images you added are beautiful, but not as valuable to the text of the article as it stands. Pictures on Wikipedia must be more than merely decorative.

I still object to adding both of these images to the article. This is a short article, with a long history of people adding pretty pictures of caustics to it. The article is just not long enough to support everyone's favourite picture of a caustic. My suggestion is that we keep the picture of the fish and caustic, because it does illustrate how caustics can be seen in nature, which is not well represented in the article now. The photo with the eel, on the other hand, does not seem to add sufficient value to the article. It should be removed. I added both images to the collection Caustic (optics) on Wikipedia Commons, however. --Srleffler 04:26, 22 September 2007 (UTC)
 * Agree.Leave a fish, remove the eel(of course the eel is interesting because the image really shows rainbow colors), but whatever.Thank you.--Mbz1 04:43, 22 September 2007 (UTC)Mbz1
 * Hmm saw this on my watchlist and decided to take a look. This isn't related to Mbz's images but more to the other images on the article. To put it bluntly they're pretty poor. I was a bit disappointed when my two shots: Image:Light through glass05.jpg, Image:Light through glass02.jpg where pulled off. I think they're better than the existing ones. If you disagree I might do a reshoot. --Fir0002 09:23, 23 September 2007 (UTC)
 * I see that it was I who removed your images, although not right after they were added. Other images got added after yours, which I felt were better. I'm not sure what you mean by "poor" here, but let me explain my reasons for preferring the images that are in the article now. This is an article on geometric optics. In this field, one is concerned with the modelling of light as discrete rays, whose propagation through an optical system can be modelled using simple geometrical analysis. As such, I feel that images that display caustics with a simple, clean geometric form best illustrate the optics involved. Your images and Mbz1's are better photographs—more beautiful, more artistic—but they are not better illustrations of the phenomenon that is the subject of this article. --Srleffler 17:33, 23 September 2007 (UTC)
 * Oh OK - I wasn't really concerned with the artistic side, it's just that the current images are very low res + noisy. And not knowing better and thinking all caustics are much alike and illustrate the point of the article, I felt that my higher quality images would be better suited and useful for users of the encyclopedia. I might try do the same style shots as in the article in higher quality --Fir0002 22:38, 23 September 2007 (UTC)

Rainbows
I'm concerned about the paragraph on rainbows. Are rainbows actually considered to be caustics? I would like to see a citation to a source that describes them as such.--Srleffler (talk) 03:16, 20 July 2009 (UTC)

The most familiar caustic is surely the rainbow, caused by the scattering of light from raindrops in the sky. In brief, the primary rainbow arises from light rays which are twice refracted and once totally internally reflected from a droplet. The scattering angle for these rays can never be less than a certain minimum value. Thus an observer on the ground sees essentially no light above the corresponding direction in the sky. The curve defined in the sky in this way is a directional caustic. Since the index of refraction of water varies slightly with wavelength in the visible, the caustics for different wavelength are formed at slightly different angles, leading to the familiar separation of colors seen in the sky.

I was concerned, too. But books to back it up are easy to find:. Someone needs to cite an appropriate one. Dicklyon (talk) 04:01, 20 July 2009 (UTC)

Differentiable inverse rendering
I started in on a rewrite of the "Differentiable inverse rendering" section to clean up the incorrect-person and sentence structure issues, but I quickly found myself leaning towards "delete". The first paragraph essentially just repeats the definition of caustic engineering already given in the section above ("Caustic engineering describes the process of solving the inverse problem to computer graphics"), but in a much more wordy way. It then starts into a presentation of one specific technique, based on some conference paper. I'm not sure who the audience for this would be. It is both too technical and too incomplete to be useful. If there is no objection, I'll just delete the whole section in a day or two.--Srleffler (talk) 04:00, 19 January 2020 (UTC)
 * No objections on my part. I agree that the material appears to be presented in a manner that attempted to simplify a complicated technique into a few paragraphs to fit within the article, and in doing so, simplifies it past the point of usefulness. WikiDan61 ChatMe!ReadMe!! 12:40, 20 January 2020 (UTC)

Pixel art.
I removed the section on pixel art. This seems to be a hypothetical application proposed in one paper. The coverage in the article was undue. The mathematical description given seemed likely to be useful to no one. Also, the first sentence was copied verbatim from the cited source, raising copyright violation questions. --Srleffler (talk) 22:36, 26 January 2020 (UTC)
 * I see this has been reinserted as "Per-pixel discrete caustic". As written, this section seems pretty much worthless. The concept is not explained well enough for the section to be useful. At the same time, there is an excess of mathematical detail that doesn't seem to convey anything useful either. Who would benefit from reading this? Further, even if the text were fixed it's a lot of text covering a single very narrow application. The article also does not establish that this is an actual application, as opposed to something hypothetical proposed by somebody in a paper.--Srleffler (talk) 01:50, 29 January 2020 (UTC)

Caustic Engineering – too technical
Many parts of the caustic engineering section are too technical, and just not well enough explained to be useful. The sections delve into the mathematics of how to solve the problem without sufficient explanation. The only readers who will be able to follow this material as it is written are those who already know the subject, and they are unlikely to gain anything from reading it here. Wikipedia is an encylopedia, not a textbook. Material that is this opaque doesn't belong here. Technical material can work, but it has to be clear enough to be useful to somebody.--Srleffler (talk) 03:42, 29 January 2020 (UTC)

make page: Jeffrey Pennington at Stanford
Otherwise we cannot elaborate his ideas. — Preceding unsigned comment added by 2A02:587:4111:63B1:4C7:98E6:6EEE:4627 (talk) 03:54, 18 July 2020 (UTC)