[HN Gopher] Everything Has Fresnel (2010)
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Everything Has Fresnel (2010)
Author : Tomte
Score : 81 points
Date : 2022-02-10 08:53 UTC (14 hours ago)
(HTM) web link (filmicworlds.com)
(TXT) w3m dump (filmicworlds.com)
| jcoder wrote:
| I don't know much about the subject matter of the post, but it
| seems like the sort of blog that would notice that the earth and
| moon in the hero image rely on the sunlight coming from different
| directions.
| [deleted]
| jerry1979 wrote:
| > I've split the specular and diffuse components with
| polarization so the diffuse is on the left and the specular is on
| the right.
|
| Does this mean the author took two pictures: one with a
| polarization lens, and a second with the same polarization lens
| rotated 90 degrees?
|
| I'm vaguely interested in what's going on here. For others who
| are interested, I think this reddit post has some technical
| details which relate to the topic:
| https://www.reddit.com/r/photogrammetry/comments/mfle5u/how_...
| _Microft wrote:
| https://old.reddit.com/r/photogrammetry/comments/mfle5u/how_...
| aktenlage wrote:
| And if so, what does it mean? I have no idea what that split is
| supposed to illustrate and how the image would have looked
| without a filter.
| twelvechairs wrote:
| Its done to split out clearly technically. Right is the
| specular component, left is excluding the specular component.
|
| Right us basically if you shined a very bright light exactly
| from the angle of reflection. Left is more similar to if the
| scene had background lighting but not from the angle of
| reflection
| aaaaaaaaaaab wrote:
| "And it turns out this happens because of a little thing called
| fresnel. [...] To account for this affect, you can use Fresnel
| [...] Certainly, PVC has a fresnel."
|
| It's called _Fresnel coefficient_ [1] after the physicist
| Augustin-Jean Fresnel. "Fresnel" is not a noun.
|
| [1] https://en.wikipedia.org/wiki/Fresnel_equations
|
| [2] https://en.wikipedia.org/wiki/Augustin-Jean_Fresnel
| GavinMcG wrote:
| I have expertise neither in physics nor in theater. But I do
| want to chime in to suggest that _any_ time you 're about to
| make a categorical statement like "fresnel is not a noun" _in
| response to someone using it that way_ , it's worth pausing.
| Regardless of your certainty, there's rarely a well-grounded
| reason to think your view is more correct than theirs.
|
| _All_ language is contextual. Fields have jargon. And _so
| many_ arguments on the internet arise when people from
| different contexts make unnecessarily strong statements
| insisting that their usage is correct. Instead, pause and
| consider whether there 's a more valuable approach such as
| curiosity.
| oh_my_goodness wrote:
| That's true, nobody needs to be scolded over choice of
| terminology, but it is a choice and it's not an arbitrary
| choice.
|
| In this case it looks like somewhere along the way, some
| (math or programming) specialists lost track of the (optical)
| knowledge that 'specular' and 'Fresnel' reflections tend to
| be the same thing. Now we're reading a complicated article
| about how maybe those two terms should coincide after all.
|
| Keeping the clunkier terminology, at least as a backup, might
| have made it easier for folks to look back and forth between
| the algorithm literature and the optical literature.
| loansindi wrote:
| > "Fresnel" is not a noun.
|
| It is in stage and film lighting [0], which made this headline
| confusing to read.
|
| [0] https://en.wikipedia.org/wiki/Fresnel_lantern
| berkut wrote:
| It's a noun in CG/VFX.
|
| "Can we change the Fresnel to get less reflection?"
|
| "No, it's a physically-based renderer - change the IOR"
|
| "but, that'll change the refraction angle..."
|
| "Yep, split them into AOVs, and let comp deal with it."
| edflsafoiewq wrote:
| Like "diffuse" and "specular", it's certainly used as a noun.
| oh_my_goodness wrote:
| Each field can make up whatever jargon is convenient.
|
| If we were talking about optics, then 'diffuse' and
| 'specular' would be adjectives that describe reflections.
| Fresnel reflection tends to mean specular reflection. The
| author sounds sensible when he recommends that specular
| reflections be implemented using Fresnel's math. That is how
| specular reflections work outside the computer.
| swayvil wrote:
| Have you ever thought about making fresnel lenses out of rippling
| fluid? Like, sound in water or whatever. Making fine ripple
| pattern for lens or diff grate.
|
| It would be kinda programmable too.
| Wistar wrote:
| I know they've thought of it using liquid crystals.
|
| https://iopscience.iop.org/article/10.1143/JJAP.24.L626/meta
| novosel wrote:
| Yes, with Chladni oscillation figures formed with
| changable/programmable vessel boundary geometries.
| corysama wrote:
| If you ever need a reminder, just watch this great video about
| V-Ray and bank heists https://www.youtube.com/watch?v=U9rgG2vPAvQ
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