That 6 min intro to the physics of light.. man its amazing. Thank you so much for actually explaining that

No need to apologize, for I absolutely LOVE your "deep dive" into the math and physic behind the different effects! These diversions give me a stronger foundation of the "why" behind the "what" happens when we change any of the settings.

To those bashing the physics explanation: The *speed* (actually velocity) of light *does* change depending on the media. speed is measured by the time it takes the light to get from point a to point b and is based on the straight line distance between the points, not the distance the light actually travels. The difference in distance often turns out to be very small, most of the effect coming from the time it takes to effect the energy exchanges between photons and electrons. On the other hand, the trick shown in the video is just that: a trick. While it mimics dispersion, it doesn't match it.

@YainVieyra

6 жыл бұрын

That's just a simplified model that we humans can use to make calculations, but the light speed is always C. It's a massless particle. That's why it's acceleration is the maximum allowed by the cosmos, which is C (Constant). If the universal constant were higher, then light would have to travel at a higher speed, because by definition its speed is always the universal constant. Even if it's simpler to say that light changes its speed, it's importante to state that the real phenomena doesn't follow that generalization and that measuring a longer time just gives you the impression that the light has slowed down, when in fact it just traveled far. Another thing to consider is that not all light passes through the material. Some photons are actually absorbed because of the impurities or because of the low energy it comes with. The white light that we are used to it's actually a whole range of photons carrying different energy amounts. Not to mention that to create a visible surface, you need trillions of photons, and that means a lot of them will be absorbed but a lot more will make it through.

@martyfouts771

6 жыл бұрын

Individual photon always travels in a vacuum and thus always travels at C, but the speed of light in a medium is not the velocity of an individual photon. Consider a source that emits a single photon into a medium. That photon may be absorbed by an electron and another later emitted. The distance traveled between such events is probabilistic and depends on the physics of the material. Each event takes a finite amount of time. Eventually, a single photon will be emitted by the material. It will not necessarily be the original photon. The speed of light through that media is defined as the length of the media divided by the time between the first photon entering and the final photon leaving. It is other than in a vacuum The speed light is defined this way, not as a simplification, but because the defined property (which relates to the velocity of any wave front in a medium) is useful.

Using this method removes the color input of the original glass shader from being accessable. To add it back you can use a 'separate rgb' node to split the input color into It's rgb components. Then plug the R into the color input of the red glass shader and so fourth.

@virtual_intel

5 жыл бұрын

I just got crazy with nodes till I see what I want 🤣

I think the reason is more about this being a way to fake the effect rather than the real way to do it. At some point Cycles will probably support bi-directional path tracing and then true dispersion would be possible.

@tobiasgehring2462

6 жыл бұрын

Bi-directional path tracing wouldn't help at all with this - the issue is that Cycles represents colours as RGB, rather than a whole spectrum. You can fake a spectral rendering engine inside Cycles as is, but it will always be faster using something specialised for that. People say that you need a bi-directional path tracer for caustics, but that's not really true either. (With enough samples) the caustics that Cycles generates are just as accurate, but a bi-directional engine would get them faster.

@Kram1032

6 жыл бұрын

Dispersion doesn't hinge on bi-directional path tracing, it hinges on spectral path tracing, which Cycles also doesn't do. Bi-Directional *would* cause caustics to clear up *way* faster.

@virtual_intel

5 жыл бұрын

EEVEE fixes that slow part 😏

@Kram1032

5 жыл бұрын

Eevee isn't a cure all and dispersion in particular can be *faked* but it won't look nearly so good as the real deal which requires slow and tedious bidirectional raytracing to happen in reasonable time.

@leaphymoon9881

4 жыл бұрын

It's been a year, does anyone know if that is possible now?

I appreciate that you went into detail about the physics behind the effect. I like your style of teaching. Thanks! I learned more than I expected.

Man, you are a rockstar! Thank you for taking the time to explain this in such a thorough way. I've understand you perfectly. Other videos out there in youtube they tend to take certain things for granted and I get lost... a lot. But you make it very clear. Thank you professor ;)

I actually enjoyed that physics bit! And thanks for the shader!

So amazing to know about the logic behind the technique, great video!

AMAZING, loving the way u explain everything, thanx.

Great tutorial! Thanks! Needed the physics lesson.

I like the way you explained this. Cool!

That you for the physics part, that was extremely import and helpful! Frankly, even if there wasn't any node after that, i still would be more that satisfied with the video.

This was a great tutorial. Just subscribed ty!!

this is really powerful tutorial!!

We went to the Monterey Aquarium recently and I noticed this sort of rainbow effect you can see on the exhibits inside the tanks. The reason for this is simple- you're looking through a *glass* tank, with *water* inside of it. In fact there was this tank where you could see through another pane of glass on the other side, multiplying the dispersion more.

Reading all the comments brings a smile to my face. Will rewatch your tutorial later on today. You seem like a good teacher. I got it on mute in bed so I gotta come back to watch it in full. Cool convo though 👍

This was really great, thank you so much.

OMG Give us more physics lessons, it truly helps :)

That's actually what I want! Thank you!

Wow, nice great work. I tried it useing the principle shader and it seem quite nice. My point for trying was for fresnel and some other calculations i believe Principled Shader does, based on Blender Guru Tutorial and so I can add color to the glass and variable IOR for other materials like diamond, amber, silica glass etc.. I saw those stuff in Wikipedia. I tried to render my test but due to my system backwardness in hardware. This is the best I could make

This is great - thanks for the tutorial !

Great shader! And it works in EEVEE also!

You are GENIOUS!!, thank you so much

Nice workaround. I like it.

Thanks, this is a great idea. Not real dispersion, but something to create very interesting effects.

This is really cool mate

thank you kindly for this video

slight correction. the speed of light IS constant however in denser mediums (like glass) it gets absorbed by the atoms more often then re-emitted. this delays the photons exit from the glass slightly however the photon itself isnt going slower. its sort of like a pitstop in a race

@arandomlizard3411

5 жыл бұрын

This is an incorrect explanation. Light only moves at lightspeed through vaccuum. Everything else, it actually does go slower.

@boriswilsoncreations

5 жыл бұрын

@@arandomlizard3411 but it only goes "slower" because of this atom emission delay

@boriswilsoncreations

5 жыл бұрын

that's why I found something wrong when he was explaining

@arandomlizard3411

5 жыл бұрын

@@boriswilsoncreations If that was true, it would be re-emmited in a random direction. And it would look more like frosted glass.

@boriswilsoncreations

5 жыл бұрын

@@arandomlizard3411 yeah it does makes sense...

8:08 Have you tried using the new Application Template feature introduced in 2.79-ish? It means you can have a separate startup file preconfigured for Cycles rendering, with nodes enabled for the default material, lamp and background, for example.

Thank you for this!~

Absolutely awesome 😎

I really enjoy your whiteboard explanations!

This is good! Just one problem: how can I apply this technique to the caustics too? On my render, they're still white, even with high level of IOR

@Sillybowler

3 жыл бұрын

kzread.info/dash/bejne/Y6RrzpuGftOylNI.html this video does caustics, and more

Hide your Rode transmitter when you're standing. Beside that, very professionnal, quick and clever. Good job.

really cool thanks

Very cool. Thanks

Amazing video

Amazing!

Awesome tutorial and explanation! Many thanks. I noticed that if I used the Mix shader node instead of the add shader node to combine the RGB light nodes, I got a very different result in the render. The object was far darker and did not look like glass. I'm curious as to why this would happen? The Mix shader fac was set at .5, so as I understand it, it basically adds them equally, no?

Brilliant tutorial, thank you. Quick question though. How would I add some colour to this mix to get different colours of gemstones like ruby, sapphire etc. I've tried various nodes and combinations but can't quite seem to make it work. Would I add something within the group or would or add it outside of the group? Thanks in advance for your help.

7:09 It’s called “dispersion” because the different-wavelength components get “dispersed”.

Yeah! I made it! Thank you!

Thank you bro!!!!

I think there is an inaccuracy in the physics explanation: White light is not primarily R/G/B but rather light consisting of R, G and B wavelengths looks white simply because the human eye only has receptors for those three colors. If the input light to a prism were just the narrow bands of R/G/B you also would get discrete bands of these colors on the other side, rather than a full rainbow. Sun light contains most visible light, but actually not all (see e.g. scied.ucar.edu/image/sun-spectrum ). This effect of working with just three colors is also visible in the shader, it produces several discrete bands, rather than the continuum one would expect for light covering the entire visible spectrum.

I love how he explains the physics. I was able to figure out the shader from that alone. Nicely done! Thank you! EDIT What's the difference between the glass shader and the principled shader with transmission cranked way up? Is one better than the other?

@Ironpants57

6 жыл бұрын

The glass shader is pretty light in comparison to the principled shader. There is a performance difference. Especially if you are adding 3 principled shaders together. The principled shader is quite like a traditional ubershader. It mixes different materials into one node. Though it does it in a way that your computer doesn't suffer. At least not as much as if you were to mix nodes together yourself.

@poppipahkina

4 жыл бұрын

Kuma Suna principled has realistic fresnel by default

Brilliant video, just what I needed! Any thoughts on dispersion values for oil?

@standingpad

3 жыл бұрын

Oil doesn't have dispersion as far as I know. It's really only prisms that have dispersion (at least at the top of my head)

Best video ever made.

I would really like to see a heat-waves effect tutorial. Nothing I've tried looks close enough.

@fab9207

4 жыл бұрын

Make a plane with smooth noise that plugs into some sort of distortion node.

You could seperate RGB from main collor to get the collors of the individual glass shader

thank you!

thanks man

Why are you so good

wow. amazing shader. i didn't know i was that big of a nerd. xD

i know this guy had a loving family growing up

is there a way to make the dispersion a smooth gradient instead of 3 separated color blocks?

I think you really ought to use more wavelengths to make it look decent. Three isn't really enough to capture this. Though that also makes mixing a lot more complicated.

Brilliant !! =)

Is this something that could be used for windows, such as a bedroom window or shower glass, or is this more for glass cubes n such?

how to see the rendered screen in blender 2.8 having issues

How did you get the background sky into the scene? My cube has nothing to reflect.

Or you can use Luxcorerender, which is a spectral renderer that supports bidirectional path tracing and there will be no need to fake the effect. It will take longer to render though.

hello, please, can you tell us, how we can create a pearl sheen?I´ve tried it with this shader and adjusted it to my lamp (I´ve splitted the light right in the same way) but it doesn´t work

That's so cool. It's like we created a custom node. That's pretty much what we did. Is there a way to port in Node Groups into another save file without redoing all of the nodes every new project?

@creativical

6 жыл бұрын

Open up blender so you get your "starter file". Then create this node group and give it a 'fake user' so it won't delete when you're not using it. Then go onto "file" in the top right corner and hit "save startup file". This way the exact file with your node group you just created will load up every time blender starts.

how can we import stuff like this in game engines like unity

When light slows down it bends towards the surface normal of the boundary and when it speeds up it bends away from the surface normal of the boundary.

works pretty well in eevee , but obviously the screen space refraction makes it a lot more inaccurate.

tnx

2:07 Better explained the other way round: refraction happens when the light changes speed, and the index of refraction in a medium is simply the ratio of its speed in vacuum to that in the medium.

@lawrencedoliveiro9104

6 жыл бұрын

3:21 That should have come first.

Hello can you make addon for Blender to calculate quantity sample need for scen depend on difference of material of objects, and position of light? For example sun out of the window and liquid water, and glases inside the room. I think this addon will be helpful for all blender people. Thank you.

Nice video! would you be able to make a Pink Floyd cover remake with this in blender?

@zemax0618

2 жыл бұрын

The pyramid, probably, the rest would belong to post processing

can you please make a caustics tutorial in Cycles?

Cool, but what if u used like 7 colors from red to indigo? Is it possible to make the transition gradual?

@boriswilsoncreations

5 жыл бұрын

yes

Actually light doesn't really change its speed (although that's simpler to assume that to explain). It has to do with the distance it has to get through. In fact the more dense is the material, the more light will bounce over atoms and so the more distance it has to do before getting out of the material. Since speed is distance/time it seems light has slowed down but in fact it has just made some more turns on its road. If you drive straight a car from point A to point B it would look like you went faster than if you drove on a road that turns a lot at the same speed. Ps:excuse my mediocre english I'm French 😅 Edit: As Theresa made me notice in the comments in fact light doesn't really bounces off atoms, this is obviously a kind of schematic representation but which is very useful to imagine in a simple way the concept of interferences which are the "true responsibles" of that phenomenon 😄

@teresashinkansen9402

6 жыл бұрын

Im not sure if it works like that. I lack the knowledge to really say but something seems off, makes me wonder why Cherenkov radiation phenomena happens when a particle goes faster than the speed of light on a relatively dense medium. Edit: i used C instead of "speed of light" but i see C is the constant of speed of light on a vacuum so i was using it incorrectly.

@blop3836

6 жыл бұрын

Teresa Shinkansen I'm pretty sure that according to the relativity nothing goes(or can go) faster than c (even if there are some theories on tachyons). However I'm not omniscient but I saw it on varuous sources and I took the explanation from the "scienceclic" channel on his video on light ("lumière" in french) if you understand french it will be much clearer than my explanation (otherwise the animations can help you understand what I mean) the interesting extract is at about 4:10 ^^. I hope this helped you 😄

@blop3836

6 жыл бұрын

Teresa Shinkansen And you're right it doesn't really work like that it is more about interferences between photons and atoms but it is much more simple to visualize a kind of "ball" that bounces off the atoms than complex interferences and this is not really far away from reality ^^

@teresashinkansen9402

6 жыл бұрын

Blop I know a particle with mass cannot go over C in vacuum but that's were i have a doubt regarding your explanation about light having to cross a longer path when going thorough a dense medium thus making it behave as if it was going slower. When a particle goes thorough a dense medium (lets say water as its commonly used on TRIGA reactors and fuel cooling pools and this effect can be seen) and its going faster than the apparent speed of light on said medium it produces electromagnetic radiation on analogy of a sonic boom so i started thinking about all this. Sadly i do not speak french but still ill try to see what i can learn, thanks for the recommendation ill check it out! Have a nice day.

@blop3836

6 жыл бұрын

Teresa Shinkansen Yes! ^^ I just saw the Cherekov radiation😄. I was going to awnser you about it! In fact in this case the particle is so powerful that it is not influenced by the atoms around, it just passes through disturbing their electronic layers (which btw creates the radiations). Since the particle doesn't have to deal with atoms it doesn't have interferences with atoms and so from an external point of view this particle seems to go faster than light. The accumulation of light that you can compare (indeed) to the sonic boom is due to the fact that the light produces by the particle is immediately slowed down by atoms and so its waves are all added. Although I do understand that the explanation of light which reduces its speed is much more intuitive at the particle scale it is not very "rigorous"(but still bery useful to understand physics at our scale 😄). I don't know if I'm very clear and I'm sorry for that 😅

Does anyone know how I could bring this texture into UE4? I have made a model for my game that uses this effect.

@eclairesrhapsodos5496

3 жыл бұрын

I see that kind of effect in RTX caustics demo in beta version.

@standingpad

3 жыл бұрын

You could bake the texture, but it'll also have any reflections and shadows that it has. A better solution if to make something similar in Unreal Engine(since Blender nodes are somewhat based on UE nodes)

Instead of RGB which corresponds to colors visible to human eye, is there a way we can use gradual hue value? This combined with gradual IOR value would give the most accurate output. RGB are the reason you're getting distinctive lines between colors. Rainbow doesn't have lines between colors. it's a spray of lightwaves with changing of different wavelength. So if we could use the whole spectrum that would be awesome

@tobiasgehring2462

6 жыл бұрын

Yes in fact there is! It takes a fair amount of samples to get good, because you need to simulate a whole spectrum of shaders instead of just three, but I've found it to still be surprisingly workable. Essentially what you want is to simulate a different wavelength of light at each sample. The way to do this is to have a really tiny noise texture of some sort, and you use the value of this to set the colour and IoR. Each sample will hit a slightly different point, get a different colour and IoR, and simulate a different wavelength of the spectrum. If you use a standard Noise texture (perlin noise), you'll have to distort the values a bit or it'll overrepresent parts of the spectrum - another option is a Voronoi texture, which I think would work fine as is, or there are some other options. If you want to get physical accuracy, you can transform the noise values to a range of actual wavelengths. Blender has a Wavelength node, which transforms a wavelength to the right colour, and you could look up the equations that give you an IoR from the wavelength (one model is the Cauchy dispersion equation). Doing it this way, you can get a smooth dispersion gradient even at very high dispersion values, and using the correct equation will make it look properly realistic instead of just a linear range. You can also look up the values for real world materials (usually given as 2 or 3 numbers).

BTW, how to change the glass color?

@cupidlsu

6 жыл бұрын

楊博皓 add a mix shader with a glass shader with ior1 of the color you want.

Great tutorial. There's always someone wanting to argue obscure technical points - usually just to show off how much they "think" they know - but your explanation covered the essentials; the rest can be relegated to a physics class.

when adding multiple glass shaders, the noise gets really really noticeable

@radoman1234

4 жыл бұрын

You mean noisybile :)

Since you just covered dispersion it would make sense to cover chromatic aberration next.

so sad that it cant make smooth mixing between disered colurs. Ive made version with red yellow green cyan/azure and blue colurs, but it takes forever to render itself and still has borders

5:37 Red, green and blue are not a fact of physics, but a fact of biology: they correspond to the three primary types of colour receptors in the (typical) human eye.

@methral

6 жыл бұрын

Facts of biology are facts of physics

@lawrencedoliveiro9104

6 жыл бұрын

Sounds like you don’t understand the difference. If you compare his renders with real-world examples of colour-fringing, you will see that the latter produce a whole spectrum of colours, not simply three separate blocks of red, green and blue.

@methral

6 жыл бұрын

I understand how lights work thanks 10 years of physics in uni.. but thanks for explanation bud ;) I still think all facts of biology and chemistry are also facts of physics. those primary types of color receptors can distinguish lightwave length cuz of minor structure differences. same of what you said just in a different scale

@lawrencedoliveiro9104

6 жыл бұрын

Your claims of comprehension fall a bit short of your demonstrated reality. Hint: there is nothing special about the number three. Some individuals are dichromats, and there are even rarer people who are tetrachromats.

@methral

6 жыл бұрын

Well dear sir/madam, first I'm terribly sorry that I can't "understand" or "comprehend" some subjects. I'm clearly not on your level. I wish you a good and happy life as I'll be crying in my bed cuz for my stupidity for the rest of my life. The least I can do is accept my defeat and retreat. I'm gonna be out of your way. Again, sorry for commenting. Have a good day

thanks @sillyroundsquare for referring me to this video

What's name of Music in intro and outro ?

i think you need more logo in the background wall, microphone, also at the microphone stand and some scattered on the table top.

Is there any way to make this shader work on Eevee? ;~;

You need to teach physics in my school that will be cool

@chborger185

5 жыл бұрын

listen PINKfloyd frontalTEACHING in a 3D enviroment B=BAD S=sucidial D=destructiv F=fool ohhh on 00:05:55 i see ;)

Im a bit confused, why do we create a disperson input in the node group? Isnt IOR controlling how much light disperses anyway?

Might I ask what you actually do wit Blender? Is this a hobby for you? Do you make commercials? VFX for movies? What do you do with it?

The problem that I faced is noise of those colors. How can I solve it?

Nice shader, but can you also teach me how to reduce the noise when using this shader? It's like super noisy all over the scene when it's on.

@manojlogulic4234

6 жыл бұрын

Hu Yande In Cycle turn on denosing option and high up render samples. Also in 2.8 with Evee it should be noise free since it's not raytrace engine. Cheers.

@dixie_rekd9601

6 жыл бұрын

eevee is not noise free. it uses approximation methods for screen space refraction which CAN be hella noisy....

@manojlogulic4234

6 жыл бұрын

AwesomeVindicator Didn't know that, thanks for replying.

@dixie_rekd9601

6 жыл бұрын

Manojlo Gulic although I've since tried to remake this shader in eevee and it's really nice looking... better than cycles in fact

@martyfouts771

6 жыл бұрын

There are (at leas) 4 things you can try in cycles. The easiest is to trust the denoiser, but there are a lot of cases where that won't work, because the denoiser will blur subtle textures. The next easiest is to change clamp direct/clamp indirect values in sampling and/or disable reflective/refractive caustics, in light paths, each of which impacts the accuracy, but you can often get away with it. Having done all of that, you can increase the number of samples, with the down side of renders taking (much) longer. The 4th way is described in the blender manual here: docs.blender.org/manual/en/dev/render/cycles/optimizations/reducing_noise.html#render-cycles-reducing-noise-glass-and-transp-shadows

Wait, I learnt in my school that white light is composed of VIBGYOR. Was I wrong about it?

Of course, RGB are not the main components of white light, just what our eyes detect. But using RGB lights look weird compared to full spectrum. Because many colors won't reflect ( try shining a RGB light on a monochrome orange color and it will just look dark)

@mechadense

4 жыл бұрын

I guess you'd need to (1) interpret RGB colors into wavelengths (having a quick look I only found the reverse option - wavelength to RGB - as a builtin node), (2) filter out way more than just a meager three bands based on a sequence of wavelength interpretation thresholds, (3) proceed as described in the video with different IOR levels and finally mixing all the bands back together. This probably needs to be done with a script node …

but how to make dispersion and caustics in cycles without noise and blurriness?

No render? :-(

Science behind blender... :)

There is a wavelength node, in case you missed it

4:58 Returning to original IOR ≡ Returning to original speed ≡ Returning to original angle.

If I render this it’s looks like a ice cream 🍦 with the disco dip…but without the ice the render looks like nothing 😅

You should sit in a room with padded walls because the echo is a bit annoying. You can also use an audio filter.