Everything Has Fresnel (2010) | Hacker News Reader

Everything Has Fresnel (2010)

filmicworlds.com

98 pointsTomte23 comments

> 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_...

See this follow-up post http://filmicworlds.com/blog/how-to-split-specular-and-diffu...

https://old.reddit.com/r/photogrammetry/comments/mfle5u/how_...

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.

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

If you ever need a reminder, just watch this great video about V-Ray and bank heists https://www.youtube.com/watch?v=U9rgG2vPAvQ

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.

Look up GE Talaria system. A projection system based on modulating oil film thickness to create diffraction gratings.

Wikipedia entry is Talaria Projector[0]; "Talaria" has no references to it.

[0] https://en.wikipedia.org/wiki/Talaria_projector

I don't know if anyone has used ripples in a liquid, but LCD's without polarizers are used in tomography to dynamically configure a diffraction or phase-shift pattern. https://en.m.wikipedia.org/wiki/Spatial_light_modulator

Yes, with Chladni oscillation figures formed with changable/programmable vessel boundary geometries.

I know they've thought of it using liquid crystals.

https://iopscience.iop.org/article/10.1143/JJAP.24.L626/meta

This person is confusing rim light on materials that are not perfectly rough with the fresnel effect, which comes from refraction at orthogonal angles that leads to reflection.

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.

"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

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.

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."

> "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

Like "diffuse" and "specular", it's certainly used as a noun.

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.

I would just call it polarization. Or if you wanted to be more specific, angle of reflection dependent polarization.

> "Fresnel" is not a noun

Says whom?

Simon

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