WEBVTT 00:00.840 --> 00:04.080 Welcome to how light interacts with a surface. 00:04.320 --> 00:10.320 So in this video you'll gain a better understanding of how word light works in the real world and how 00:10.320 --> 00:13.830 it transfers across into the cycles rendering engine. 00:13.860 --> 00:18.070 Now we've already got a rough idea when it comes to plain surfaces. 00:18.070 --> 00:25.350 And we started building that up by mixing shaders together and we starting to change how light interacts 00:25.350 --> 00:32.120 with the surfaces depending on the angle of which is viewed from or even just with a texture applied. 00:32.120 --> 00:38.940 So we're starting to control how that light actually is being reflected and seen by the cycles rendering 00:38.940 --> 00:39.470 engine. 00:39.570 --> 00:43.520 And that's how we can start building up more and more realistic materials. 00:43.800 --> 00:48.390 Now we're going to look at six ways that light and surfaces can interact. 00:48.450 --> 00:54.390 And of course in real life they don't just act him one way they act in multiple ways. 00:54.480 --> 01:01.020 Also going to gain some understanding about the physics behind how our materials are working and don't 01:01.020 --> 01:05.060 worry we're not going to get too deep into the maths behind it. 01:05.070 --> 01:11.370 So in order to start this we're going to grab a pen and pencil or in this case a digital version of 01:11.370 --> 01:15.690 it and start having a look at how light interacts with the surface. 01:15.810 --> 01:21.800 Okay so in front of us here we have six different setups in front of us. 01:21.960 --> 01:31.440 And these are suppose are analogous to the having a just a a a rectangle there with one individual shader 01:31.440 --> 01:32.600 attached to it. 01:32.760 --> 01:38.880 So for instance reflection now when reflection happens and we've covered this right earlier on in the 01:38.880 --> 01:45.370 course when we started talking about shaders we have the angle of incidence where the light comes in. 01:45.420 --> 01:46.690 So the angle here. 01:47.750 --> 01:51.070 Is it called the angle of reflection. 01:52.020 --> 01:56.030 Of course nothing is a perfect reflector in the real world. 01:56.220 --> 02:00.340 So this is a perfect example. 02:00.360 --> 02:03.860 In reality you would end up mixing it with something else. 02:03.870 --> 02:08.160 And in fact that's what we're aiming to do here to get a little bit of a deeper understanding what's 02:08.190 --> 02:14.280 actually happening to light when it hits the surface so we can set up more realistic material so we 02:14.280 --> 02:17.060 can think more in-depth about what is happening. 02:17.430 --> 02:18.300 So scattering. 02:18.300 --> 02:19.970 So for instance here diffuse. 02:20.160 --> 02:24.690 So we have again the light ray coming in but instead was a bit of a wobbly light ray. 02:24.780 --> 02:30.870 We would have it scattering off in different directions at different magnitudes depending on the surface 02:30.870 --> 02:31.800 itself. 02:31.920 --> 02:35.850 And that is very useful when we combine the two. 02:35.850 --> 02:41.580 Of course if we did combine the two you may end up with a big reflection coming out if it was quite 02:41.580 --> 02:48.890 a glossy surface and some diffuses well and that would be a mix of these two put together. 02:49.530 --> 02:54.210 Of course then we can add other things into control how that mix happens and that's what we've been 02:54.210 --> 02:56.350 doing very recently. 02:56.400 --> 03:04.050 Now what happens with absorption well as it sounds as light hits a surface some of it will be absorbed. 03:04.140 --> 03:06.250 It's just the way the world works. 03:06.360 --> 03:09.820 So it'll go into the material and be lost forever. 03:09.960 --> 03:14.610 Now it won't be everything that gets lost because that's impossible. 03:14.610 --> 03:19.510 Mass is a black hole which case this would be an entirely black material. 03:19.530 --> 03:25.350 No we're talking earlier about not having materials that was zero on anything. 03:25.350 --> 03:31.400 So let's say green or white light hits the surface and some green is absorbed. 03:31.830 --> 03:35.240 That means we've got the blue and the yellow. 03:35.240 --> 03:37.870 So we have a little bit of the blue and the red. 03:37.920 --> 03:40.130 We have a little bits reflecting here. 03:40.290 --> 03:48.740 Red might come in and get absorbed a little bit but be reflected off much more or bounced off or whatever 03:48.750 --> 03:50.230 it happens to be. 03:50.310 --> 03:56.340 And then of course the blue light itself if that also struck the surface that may be the biggest one 03:56.340 --> 03:56.780 of all. 03:56.790 --> 03:59.610 And that would be a kind of a a pinky colour. 03:59.640 --> 04:07.500 Overall it would be somewhere around here probably would get that type of shade or this particular material 04:07.530 --> 04:11.460 would look a kind of magenta in colour. 04:11.970 --> 04:18.630 Now refracted that is an interesting one you can do this at home when you stick a pencil or a straw 04:18.660 --> 04:20.300 into a cup of water. 04:20.430 --> 04:26.570 You'll see light comes in and then it will bend towards or away from the normal. 04:26.700 --> 04:33.240 So we've got our normal running through here either burn burn turn towards it or away from it depending 04:33.240 --> 04:38.350 whether it's entering a less dense material or a denser material. 04:38.580 --> 04:44.490 So if it's more dense it will tend towards the north of it's less dense it will tend away from that 04:44.490 --> 04:45.220 normal. 04:45.450 --> 04:49.590 So if it was going from glass into air we would find that out. 04:49.620 --> 04:50.820 Well let's do that. 04:51.030 --> 04:53.820 So in from air into glass would do this. 04:53.880 --> 04:59.510 And then as it struck the other side it would carry on roughly at the same angle it was before. 04:59.760 --> 05:02.390 So it slows down and then picks up speed again. 05:02.610 --> 05:09.690 And now this here that we've just drawn is an example of transmission where light doesn't have to be 05:09.690 --> 05:10.770 refracted. 05:10.770 --> 05:17.700 The majority of the light that enters an object goes through that surface and comes out the other side. 05:17.700 --> 05:19.790 Now of course it could be transmitted. 05:19.950 --> 05:24.400 And instead of coming out in a straight line it might be scattered on the surface. 05:25.450 --> 05:31.650 Incidentally when things go inside a model you can end up with subsurface scattering. 05:31.660 --> 05:33.730 So we go back to scattering up here. 05:33.790 --> 05:39.700 If this was a subsurface scattering node we'd find that light would enter the material and then bounce 05:39.730 --> 05:43.110 around and some of that light would find its way out. 05:43.180 --> 05:47.090 And some of it would be absorbed as well. 05:47.110 --> 05:50.350 So there's a lot that joins all of these things together. 05:50.470 --> 05:55.680 Now some of the particular shader nodes that we have are to make our lives easier. 05:55.860 --> 06:00.990 Before a while not that long ago actually the subsurface scattering node didn't exist. 06:01.210 --> 06:08.920 And before we had to do a mixture of all of these things blending them together to try and get a subsurface 06:08.920 --> 06:12.020 scattering or something that at least emulates it. 06:12.130 --> 06:18.190 The final one here there's no direct shade before but it happens in real life and it's worthwhile knowing 06:18.190 --> 06:18.970 about it. 06:19.000 --> 06:25.570 So when light or energy would hit piece surface and let's say it gets absorbed and it gets absorbed 06:25.600 --> 06:30.450 almost fully with very little reflections so we get most of the energy coming in. 06:30.820 --> 06:37.030 Now this particular object would have absorbed energy so it will start emitting energy as well. 06:37.030 --> 06:40.260 Now usually that would be infra-red energy or something along those lines. 06:40.270 --> 06:43.760 But it could also be visible light if it was energetic enough. 06:44.080 --> 06:48.530 So we can't really do the radiated by a shader. 06:48.640 --> 06:53.050 But I think the closest thing to that if you were to emulate something that was hot perhaps something 06:53.050 --> 06:59.710 that was glowing because a lot of energy had been put into it it would be radiating to be emitting so 06:59.710 --> 07:03.190 an emission shader would be quite a useful one here. 07:03.230 --> 07:08.620 I'm sure you could set up a couple of maths nodes and other things to calculate a certain amount of 07:08.620 --> 07:12.920 radiation depending on light hitting the surface as well. 07:13.180 --> 07:18.950 So let's go have a closer look at some shaders now and hop on over into blender. 07:19.950 --> 07:22.520 Okay so we're on a default blender file here. 07:22.620 --> 07:28.380 And one of the things we can do to try out these different Shaila types and then turn snapping on an 07:28.420 --> 07:35.520 With lift this object up by one and move it across a couple are now going to go to the 3-d cursor where 07:35.520 --> 07:39.410 are we 3D Curson just set it plus one on the z axis. 07:39.410 --> 07:48.590 So when I add a couple of more basic objects like a cone and Suzanne let's stop at Suzanne the monkey. 07:48.600 --> 07:49.240 There we go. 07:49.380 --> 07:55.500 And we rotate Suzanne around 90 so she's facing us although that is down the camera. 07:55.500 --> 07:56.920 She was rightly added. 07:56.950 --> 08:03.570 I want to set smooth shading on this cone so smooth shading there will get some odd effects around the 08:03.570 --> 08:09.120 base here because well it's trying to smooth around a great of a 90 degree angle so that's going to 08:09.120 --> 08:15.330 look interesting and I'm going to smooth Suzanne here now with Suzanne one of the things to bear in 08:15.330 --> 08:22.260 mind is she's going to be quite jagged So I'm going to add in a couple of subsurface divisions just 08:22.260 --> 08:24.510 to make her look that much smoother. 08:24.840 --> 08:32.940 Okay let's go to the camera view and well let's move that camera around so we've got a much better view 08:33.660 --> 08:35.590 case of all three of our objects. 08:35.620 --> 08:42.690 Now finally to play with this I'm going to add in one final meche So I've got a surface to work with. 08:42.690 --> 08:46.010 Going to move that down and scale it up. 08:46.020 --> 08:52.770 So we've got a surface and I'm going to set all three of these objects to have the same material. 08:52.770 --> 08:59.140 So let's go to the materials tab new and let's change the colour so we can see what's going on. 08:59.160 --> 09:05.090 Ullman could apply that material to all these other ones as well. 09:05.310 --> 09:07.090 Okay so we've got our material set up. 09:07.170 --> 09:12.870 Lighting is not great at the moment so when I go to my lamp maybe it universal using the sunlamp and 09:12.870 --> 09:14.180 use nodes. 09:14.220 --> 09:14.850 Okay. 09:14.850 --> 09:21.330 And I'm going to make the outputs of the strength about four so it's nice and bright when I get rid 09:21.390 --> 09:26.660 of my propertys panel and my tool shelf and just zoom into the area we're looking at. 09:26.790 --> 09:32.790 Now we've got this set up we can actually play with the material and I'm going to call this test material 09:32.800 --> 09:38.160 so we know what's going on and we can actually change this to all different types so we can make it 09:38.190 --> 09:43.980 glossy You can see this reflecting Incidentally you see this really jagged stuff happening around here. 09:44.070 --> 09:49.350 That's simply because there's there's not enough polygons to interpolate between them all so you end 09:49.350 --> 09:51.200 up with a very jagged surface. 09:51.210 --> 09:56.880 If we wanted to improve that again we'd have to add some subsurface divisions but of course with that 09:56.880 --> 10:04.080 comes a few problems in itself because that cone no longer looks like a cone but kind of cool it now 10:04.080 --> 10:08.120 looks like a teardrop which I didn't know that would happen. 10:08.130 --> 10:09.120 First time I've tried that. 10:09.120 --> 10:09.810 There we go. 10:09.810 --> 10:10.900 How cool is that. 10:10.920 --> 10:14.520 If I'm going to move that across on the y axis so it's a little. 10:14.580 --> 10:20.520 I've moved the wrong thing move across on the y axis it's a little closer to our models. 10:20.700 --> 10:24.810 Okay I'll leave it like that just because I can and because I quite like it. 10:25.040 --> 10:29.260 Okay Somehow I've got these three objects that we can play with. 10:29.340 --> 10:36.000 We can play with the materials and I'll get to that in a few moments after I've just explained a couple 10:36.000 --> 10:37.340 of items here. 10:37.470 --> 10:47.400 So I want to explain that why volume absorption and volume scattering will come out black and anything 10:47.400 --> 10:48.800 else to do with volume. 10:48.810 --> 10:56.470 And the reason for that is because we're changing the volume properties and not the surface properties. 10:56.760 --> 11:03.300 So we see the word surface here and volume here so we can swap these round or essentially click on the 11:03.300 --> 11:10.240 little darton remove and then go to volume and add it in to volume absorption for instance. 11:10.530 --> 11:14.810 And if I make this density something like 15 we'll be able to see what's going on there. 11:14.820 --> 11:20.050 The thicker your object is the more light it's actually absorbs. 11:20.160 --> 11:22.640 So we give this a colour let's make it a blue. 11:22.710 --> 11:28.620 We can see that's we end up with a very dark blue or essentially black if all the light is absorbed 11:28.860 --> 11:32.070 by the time it reaches the middle of a thick object. 11:32.070 --> 11:35.910 And these is a quite thin so it lets a lot of light through. 11:36.030 --> 11:41.850 Now volume scatter is very similar but it's kind of opposite in a way. 11:41.880 --> 11:45.450 So you're telling it which colours are being absorbed. 11:45.450 --> 11:50.340 So in this case the blue you can see opposite is the yellow surface absorbing a lot of blue and the 11:50.340 --> 11:51.780 output is mainly yellow. 11:51.780 --> 11:57.690 If I tell it to absorb all the green and of course don't go all the way because otherwise you'd get 11:57.690 --> 12:01.930 a complete zero on something and which is something we don't want. 12:01.950 --> 12:09.720 If we go let's say to here we can see that the pink light is being scattered etc etc etc. says the opposite 12:09.720 --> 12:11.340 side of that colour wheel. 12:11.800 --> 12:16.150 Now when we look at the nodes set up we get something. 12:16.230 --> 12:19.050 Well it really highlights what's going on in the background here. 12:19.310 --> 12:25.670 So if we're playing with the volume scatter it needs to be plugged into the material outputs in these 12:25.670 --> 12:31.760 to be plugged into the volume inputs of that material outputs otherwise it won't work and it actually 12:31.760 --> 12:35.240 says here volume and we've got a green shader outputs. 12:35.360 --> 12:38.360 So it's looking for a shader input that's also a volume. 12:38.400 --> 12:42.950 If we plug it into a surface it doesn't work because it's not set up to do that. 12:42.950 --> 12:49.890 The other thing to show you guys is the anisotropic filter. 12:50.060 --> 12:52.780 Where is that anisotropic in this tropic. 12:52.850 --> 12:54.810 I'm being complete we go. 12:55.020 --> 13:01.490 So anisotropic basically means it changes depending on the direction at which the camera and slash lighting 13:01.790 --> 13:03.500 is hitting the object. 13:03.500 --> 13:10.060 So in this case an anisotropic is used as a control here and a stroppy amateur tropica I don't know 13:10.060 --> 13:13.820 how mispronouncing that amateur trophy up anyway. 13:13.910 --> 13:16.810 It depends on the handler which the light is. 13:16.850 --> 13:21.290 And we end up with a very good looking saucepan lid. 13:21.320 --> 13:24.080 If we get the settings quite right there. 13:24.290 --> 13:29.150 Perhaps not on a cube but we get the effect there if you look on the bottom of a metallic saucepan of 13:29.150 --> 13:30.240 what's going on. 13:30.260 --> 13:37.720 So it's very very good for metallic objects it's basically directional reflections in that case rotation. 13:37.730 --> 13:42.720 Well that kind of skews that and makes it look a bit odd in places. 13:42.740 --> 13:48.340 But it will have its its time and place depending on the model that you're working on. 13:48.860 --> 13:51.740 So that's only a couple of these shaders gone over. 13:51.770 --> 13:54.700 And of course it's time for a challenge. 13:56.130 --> 14:03.600 I would like to go and play with shaders so set up a series of basic objects just use primitives to 14:03.600 --> 14:10.200 get the hang of this and obviously watch for facets as well so if you are going to use anything that's 14:10.230 --> 14:15.520 basically smooth you want it to be as smooth as possible in the first place. 14:15.540 --> 14:23.130 So bear in mind if you're making a sphere or you're making a cone etc. just to make sure you don't have 14:23.190 --> 14:29.730 artefacts when your rendering apply the same shader to each one of these objects you can see how it 14:29.730 --> 14:33.970 affects different objects at the same time. 14:34.020 --> 14:38.790 Remember you can use a render board has to speed up rendering so you have to render the entire scene 14:38.790 --> 14:44.010 you can draw that render border around your work so you don't have to wait for your computer if you've 14:44.010 --> 14:46.920 not got a particularly quick one to render the scene. 14:47.060 --> 14:52.050 Remember you can lower your samples as well just in case you've turned them up at some point in the 14:52.050 --> 14:52.740 past. 14:52.770 --> 14:56.330 I wouldn't recommend any more than 10 wash to do in this testing. 14:57.470 --> 15:03.680 Try out all of the shaders one by one to see their effect on those primitives on those objects and you'll 15:03.680 --> 15:07.020 get an idea and a feeling about how they're going to work. 15:07.100 --> 15:14.660 When you start using them on other objects as well remember volume shaders need to be plugged in to 15:14.660 --> 15:17.860 the volume input of the material output node. 15:17.930 --> 15:23.440 They're designed to work on the volume of the shape not just its surface. 15:23.620 --> 15:26.430 So a video now and give that a go. 15:28.870 --> 15:29.540 Okay guys. 15:29.560 --> 15:30.550 Welcome back. 15:30.550 --> 15:32.490 Let's go play with some shaders. 15:33.540 --> 15:37.530 Okay so we're back over in blender and I'm going to go and open up a file. 15:37.530 --> 15:41.070 I was working on earlier just a few extra primitives in it. 15:41.190 --> 15:41.960 And here we go. 15:41.970 --> 15:47.630 We've got smooth shading applied to four of the objects here and the others are flat. 15:47.760 --> 15:51.360 So let's hop into rended mode so we can see what's going on. 15:51.360 --> 15:56.900 And I have got the man lights a peachy creamy colour at the moment. 15:57.090 --> 16:01.110 So with diffuse we know what that looks like we'll play with that. 16:01.120 --> 16:03.450 Lots hair does look very odd. 16:03.450 --> 16:08.000 Did you notice that when you played with hair he heads up faceted all over the place. 16:08.040 --> 16:13.460 Of course this shader is in fact designed for hair not thick objects. 16:13.530 --> 16:14.550 But there we go. 16:14.700 --> 16:18.050 If that's a pattern you're looking for and something. 16:18.160 --> 16:21.470 Well it's there and ready for you if you want to use it. 16:21.510 --> 16:22.930 So let's see what else we got here. 16:22.930 --> 16:24.160 Volume absorption. 16:24.180 --> 16:27.970 Of course we can't use that on the surface we need to use that on volume. 16:27.980 --> 16:30.020 That was great fun to play with glossy. 16:30.030 --> 16:32.370 I always love glossy I like shiny things. 16:32.370 --> 16:33.770 Call me a magpie. 16:33.900 --> 16:38.910 I can make things reflective and we've already played with making this roughness just a little bit more 16:38.910 --> 16:45.380 sensitive before I quite like the tune shade whereas it bit the further downtown. 16:45.530 --> 16:47.310 Now I thought this is quite cool. 16:47.310 --> 16:50.550 Give us a more cartoony appearance to your models. 16:50.740 --> 16:53.080 And there were two options here. 16:53.180 --> 17:01.650 Diffusive glossy glossy had a much harsher reflection to non reflective area I suppose that's right 17:01.680 --> 17:09.540 with it being glossy size I quite liked having that quite high up because it gave more of that comic 17:09.540 --> 17:17.290 book type feel to its core smoothing just made those those boundaries a little less harsh. 17:17.370 --> 17:23.460 Although when he wakes up a size so high it didn't really make sense raising the smoothness because 17:23.460 --> 17:29.390 it made it quite bland by quite like the the output that this gives a very cartoony very. 17:29.430 --> 17:35.950 That's basically what it is it's a toon shader it's supposed to look more cartoony velvet's now. 17:36.050 --> 17:39.860 It was an interesting one for me that kind of looked more like. 17:40.290 --> 17:42.860 Well obviously it's supposed to be velvet so why. 17:42.930 --> 17:46.680 Let's make it a luscious deep red or gorgeous. 17:46.800 --> 17:54.220 But it reminded me more of the diffuse shader with the black splodge facing the camera than about you. 17:54.240 --> 17:57.170 But that's how I felt about it when I first saw it. 17:57.330 --> 18:04.560 Now I do know that it's useful for doing surfaces that have a house slightly hairy like fine the hair 18:04.560 --> 18:06.500 on a face or something along those lines. 18:06.600 --> 18:13.890 So it can be used much more subtly than this extreme example translucent that's always fun to have. 18:13.890 --> 18:16.520 Of course these are designed to. 18:16.530 --> 18:23.160 Some of these are designed to be used with other shaders so translucent as the main sounds is just letting 18:23.160 --> 18:30.240 light through our model which is great but of course it would be better if it was mixed with something 18:30.270 --> 18:36.160 else to make it semi transparent glass is a good one to play with. 18:36.180 --> 18:43.980 Now there are shader itself has got some spec clarity to it so it's glossy and refraction down in the 18:43.980 --> 18:50.360 bottom is basically the glass shader without reform without the gloss added to it. 18:50.460 --> 18:58.350 So very similar but this is more of a I suppose a plastic sort of feel to it rather than a glass. 18:58.350 --> 19:05.880 Now the one that will get most people is hold out because you're very unlikely to use it unless you 19:05.880 --> 19:09.320 are trying to separate something out later on in the compositor. 19:09.480 --> 19:16.650 Essentially hold out adds a value of zero for any object that actually has that material applied to 19:16.650 --> 19:17.110 it. 19:17.220 --> 19:24.060 And when that happens it means that later on you can fill it in in a render in the compositor. 19:24.060 --> 19:28.430 But we're not going to use that in this particular section at all. 19:28.470 --> 19:30.540 So lots of different ones to play with. 19:30.540 --> 19:32.870 Did you have any particular favourites. 19:32.960 --> 19:38.830 Say I quite liked to know that was one of my favourites because it had that high contrast to it. 19:38.880 --> 19:42.440 Did you end up mixing or adding any of the shaders together. 19:42.440 --> 19:44.750 Did you get some effects that you really liked. 19:44.880 --> 19:50.400 I quite like mixing emission with certain shaders because it makes the objects glow as I said I like 19:50.400 --> 19:52.170 shiny things. 19:52.290 --> 19:57.190 Anyway if you've come up with some great shader combinations I'd love to see them in the discussions 19:57.510 --> 20:00.140 and I will see you guys in the next lecture.