Improved Coatings in Blender 4.0

in this video we're going to talk about changes to the clear coat function in blender 4.0 it's now been renamed to be simply code in order to talk about code we first need to talk about how it relates to the Shader setup within the principled bsdf bsdf stands for bi-directional scattering distribution functions which is a set of mathematical functions that describe how light is scattered by a surface the principled bsdf has two sub-categories of scattering functions one dealing with reflected light a brdf and one dealing with transmitted light a btdf brdf stands for bi-directional reflectance distribution function the principled bsdf has a four-tiered brdf reflectance model where the base coat is either a diffuse layer or it can be set as a metallic layer with varying degrees of roughness sitting above that is the next brdf layer the specular layer Which models glossy Reflections and is governed by the index of refraction third tier brdf is the coat layer which sits above both base and specular coat acts like a coating on a Surface like a clear finish with the most notable example being a car paint that paint protective varnish-like layer designed to protect the paint of the car this layer is also governed by the fresnel curve and has its own index of refraction however the coat layer can also be made to act like the specular layer by adjusting its roughness the fourth tier is Sheen and is used most often for Fabrics but when used on hard surfaces can act as a dust-like layer all four layers can be active at the same time in 4.0 some key changes have taken place to the coat brdf to improve its functionality number one in 3.6 decoding function used to reflectance model called gtr1 but it's been changed to use the more common ggx algorithm for visual consistency with the specular layer number two the coat function is now properly energy conserved which is a really big deal number three coat now has its own ior value whereas in 3.6 it was hard-coded to 1.5 using a proper index of a fraction value to control the coat function is now more physically accurate number four 3.6 had a single clear coat parameter whose purpose was to set the F 0 end of the fresnel curve the curve was hard coded to an ior of 1.5 this had the effect of setting the Coatings overall intensity and appearance but it also acted as a scalar value and Its Behavior wasn't entirely clear or obvious it was abstract and unclear with the value actually meant from a user standpoint unless you knew what a fresnel curve was in 4.0 the clear coat parameter has changed and is now called weight it's now a scalar value with 1.0 being the full expression of the fresnel curve which in turn is controlled by the code ior this is now user definable Zero Turns the code function off the takeaway from this is that the weight function allows you to either turn code off or to easily adjust the intensity of the coat from function but if you are familiar with using an ior to control the fresnel curve you can simply set weight to 1.0 and adjust the ior to increase or decrease the strength of the coat function so it's more physically correct to use the ior to control the Cove function the weight parameter will affect both the F0 and f90 and the fresnel curve muting the overall reflectiveness of the coat property whereas the index of refraction will adjust only to F0 end making it more physically accurate so the wave function is more of an artistic control while the ior is more of a physically accurate control number five a new tinting mechanism is available that uses a volumetric absorption function within the simulated thickness of the coat layer this models the way light refracts and absorbs light and is set with the temp parameter this provides a new way to apply Hue shifts to a surface but it's important to note that the reflections on the tinted coat layer are uncolored the tinting sits below the coat Reflections but it does affect everything that sits below including diffuse metallic subsurface specular and transmission layers so let's take a look at example where I've got this white silverish metal material where I then add a very slight blue purplish tint to it and you get this you can see with that color being very subtle and very light it still has a perceptible change to the Hue of that white silver metal in this next example we've got this strong red base metallic layer when I add a very similar slight purplish bluish very pastel light colored to the tint you get this sort of pinkish purplish shift in the Reds it adds just a very interesting Dimension to the red in this next example we start off with a yellow goldish color and by adding a somewhat stronger tint to it we shift it over into this beautiful amber color let's jump in and actually look at blender right now so far I've been doing a lot of lecturing now let's do some Hands-On what we want to do is transfer a file from 3.6 over to 4.0 one that contains some objects that have coating or clear coat as it's called in 3.6 and we're going to move it over to four to see what happens so that we can make sure that we understand that I'm using blender 3.6 I've set the theme to light and blender 4 will be the standard Dark theme when we look at the clear coat function for the object that I have selected we have a value of 4 and as I mentioned earlier in the video that meant that it took the fresnel curve the F0 end and it set it to four percent reflectivity well the curve itself is defined by an index of refraction that if it's 1.5 automatically has a low end F0 reflectivity of four percent but what the developers did was they made it so that you as the user could sort of configure that low end value which is what tends to define the overall look in terms of intensity for Reflections on a surface and they let you configure it so if you wanted it to be a lower value or if you wanted it to be a higher value you could just do that but it was never really apparent what was happening but in fact that's all it's doing is it's setting the low end manually and then it's just compressing or expanding the fresnel curve to fit that low end value that we're setting but the curve that was being expanded or contracted was simply the 1.5 5 curved shape if we bring this over into 4.0 we get the new user interface so we can see that it now has new tabbed interface elements so if we come down to coat and we look at this we can see that weight is 1.0 it's got the roughness and it has the index of refraction which we did not have before now it could be confusing because if we jump back over to 3.6 there in fact is an index of refraction right there sitting underneath clear coat roughness but this was only tied into transmission and it didn't even affect specular Reflections it was untied to both of those and so be very aware that when you bring it in this ior value is not the same as the ior value that you see right here and this is really important to remember so how did we go from a value of 4 in blender 3.6 to a value of 1 over here in blender 4.0 well it makes sense if you remember earlier on the weight factor of 1 just means that the index of refraction is what governs the degree of reflectivity for the coat function meaning an index of a fraction of 1.5 produces an F 0 degree of reflectivity of four percent and so when 4.0 opened this file it saw that value of 4 from our 3.6 file and said oh that means the index of refraction is totally governing the reflectivity and it put the value here at 1.0 so let's test this Theory let's jump back over to 3.6 and change this clear coat value cut it in half to a value of 2. now let's save this let's jump back over to four and what we do is we just do a revert and it will reload that file okay so let's open code back up and there it is we have the weight of 0.5 so blender four said I see an incoming value of 2 for clear coat an index of a fraction of 1.5 produces four percent at F zero therefore the user must want a weight of 50 percent of what the ior 1.5 would produce by default so that's how it works Let's test this again let's come back in come back to 3.6 and we're going to do we're going to go the opposite direction let's do eight which increases the intensity double and then let's save this and then we're going to come back over and look at that now the weight is a factor of two because it so it took the default F0 reflectivity of four percent saw that it was eight in the previous version and said oh you must want the weighting to be 2.0 so one of the other changes that I mentioned was energy conservation this is a really big deal and it's really important so here is the same file in 3.6 just this really basic testing file that I use and you can see this white slab against the dark background is both reflective at a diffuse level and at this clear coat level and it seems kind of glowy so now let's take a look at what this does in 4.0 with the energy conservation you can see that the 4.0 version got darker but it's not just that it got darker in some random way it was preventing too much energy from reflecting off the surface and 3.6 was allowing that to happen let's take a look at one more quick example of this energy conservation before we move on I actually used this in my first video on energy conservation so this is 3.6 without energy conservation I want your eyes to look at the perimeter of these shapes these have a metallic layer underneath the base layer and then a coating on top in 3.6 Coatings were not energy conserved now when we take a look at this in 4.0 we get this you can see it apparently darkened because at high glancing angles it was correctly balancing the amount of energy and so it wasn't allowing too much energy to leave the surface this is a really important thing for realism in renderings okay it's been a bit of a journey getting to this point but let's come into my material tester and let's just play with configuring this we're now officially into beta territory so the user interface has been changing a lot over the past month and it should be pretty stable by this point so I've turned off specular so we have basically a white diffuse surface and the process that we're about to go through is basically the process you would go through to set up car paint as an example so we're going to change the base color let's make it a yellow a really sort of Rich yellow I'm going to take its intensity way down so it's pretty muted but we want the undercoat not to be fully diffuse many many car paints are very metallic so a key characteristics of metals is that their Reflections are heavily tinted to the color of the metal so we need to take this into metallic mode but our roughness is quite low so we want to increase the roughness now what we want to do is add another layer on top of it we're going to come over to coat we're going to turn the weight up to 1.0 and there we go we have our Coating in place so the first thing that we want to do now is come in and consider whether the Coatings Reflections are too strong or not strong enough I'm going to bet that maybe we want them to be just a little bit more subtle so I'm going to come down to the ior and set that to 1.33 that is going to produce about a two percent reflectivity face on at the F0 position and there are very good reasons to use the index of refraction because it's a physical value there are many many described and charted values for lots of substances that have very specific indices of refraction that you can plug in and use for the sake of demonstration I'm going to set this back up to the slightly stronger 1.5 so let's consider adding a tint now that would be sort of the last thing that you look at the first thing that you want to remember is the fact that you want your tint color to be very slight and kind of ephemeral otherwise it will very quickly overwhelm whatever colors are underneath it so let's just play with the very slight sort of complementary color to this goldish yellow that we have and we're going to push it over there and what you're going to see is subtly it shifted that color from from a really rich gold into a gold that's kind of shifted towards the greenish because we've added a little bit of the blue tint to it and remember it's not the reflections on the coating layer that are being tinted it's what's underneath the reflections that are being tinted so it's going to heavily influence everything underneath it so if we come over and we let's just let's just experiment with some other colors and you can see the effect that these just very subtle colors have on the tonality of that gold now keep in mind that if you start getting into these very very rich colors to the outside of the wheel it will very quickly overwhelm the underlying base colors that you have so just sort of keep that in mind now one final thing that we're going to look at here is how Coatings can affect the look and feel of your glass types of materials so let's come down to our coat and let's give it a slight blue feel to it so I'm going to shift up just very slightly Into the Blue look at that isn't that interesting now you can come in and play with it you can see saturation is way down here so I'm going to take saturation and drop it way back so it's just like just subtle but look at what that does to that glass it really gives it some character by doing that I hope you found this to be a useful introduction into the updates that have happened to the coat slash Coatings function in blender 4.0

Channel: Christopher 3D

Views: 17,982

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Id: f0y8yOmJgd8

Length: 16min 20sec (980 seconds)

Published: Sat Sep 30 2023