
Shadertoy Path Tracing: Fresnel, Rough Refraction and Absorption, Orbit Camera - ingve
https://blog.demofox.org/2020/06/14/casual-shadertoy-path-tracing-3-fresnel-rough-refraction-absorption-orbit-camera/
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MrMid
This is part 3. Part 2 discussed here:
[https://news.ycombinator.com/item?id=23445575](https://news.ycombinator.com/item?id=23445575)

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jasondclinton
Amazing and made to look so accessible. I love posts like these.

FWIW, this ShaderToy doesn't seem to work in either Firefox or Chrome for
Android. Had to view it on a Linux machine.

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uinerimak
This is a great article. Thanks for the effort. Just one thing; can you
explain absorption, please? Is that just the fact that darker materials absorb
more light?

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n3k5
As Alan says in the article, ‘“absorption” […] means that light is absorbed
over distance as it travels through the object.’ So you can make an object
darker by increasing the material's attenuation of light going through it, but
it'll also become darker when you keep the material the same, but scale the
object to a larger size.

This is introduced together with refraction because, in that context, it's
important for rays that go through the object, as opposed to bouncing off the
surface. When you look at diffuse reflections, darker materials also
technically absorb more light penetrating through the surface than lighter
ones. The difference is the scale at which the effect becomes significant
enough that you want to spend computations on simulating it. A piece of rock
doesn't change brightness when you scale it up — unless you're looking at
grains of sand. With clear water it's the opposite: You don't need absorption
to render a cup of water, but you do need it to render a lake.

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photawe
Seems HN brought shadertoy to life big time. Really hard to connect to the
site :)

