Work with emissive shaders in Arnold - Maya Tutorial

- [George] Hi, I'm George Maystree and today we're going to take a look at emissive lighting in Arnold. Now emissive lighting is just one of two ways that an object can emit light in Arnold. You may be familiar with mesh lighting. Which is probably the more common way to do it, but you can also use the shader to emit light, and that's called emissive lighting. So here I have a simple scene here, and I've got a couple of layers here. I've got some layers for these lights, and then a layer for this neon sign. So we're going to start off with the neon sign. So I'm going to go ahead and select it, and then go into the attribute editor. Now I have an AI standard material applied to this object, and if we were to render it, well we wouldn't get much because it's, basically there's no lights in the scene. So here's the blank render. So there's really no light in this scene. So I'm going to go ahead and save this out, and let's go ahead and actually add some light using emissions. So I want to make sure that I have my object selected. Just go into that AI standard eight material, and if we scroll down, you should see an emission rollout. Now this has two things. It has color and scale. So I'm going to make the color the same color as that light. Which is kind of a cyan color. And then i' going to turn the scale up to one. This is basically a brightness control or relative brightness control on the shader. So you can have something emit a bunch of light, which would be one, or a little bit of light. So maybe .1 might be a good way to simulate ambient lighting or something like that, but we're going to go ahead and just pull this all the way up to one, and let's go ahead and just do another render. So here's the result of the emissive shader, and as you can see, we've got some light in the room. Obviously the neon light itself is lighting up, and we get a nice cast of light in the room. So as you can see, we went from completely dark, to this. So this is a good start. Now you may want to think that maybe you can use this to light an entire room, and that's not really how this is designed. Emissive lighting isn't really as accurate as mesh based lighting. So let me show you the difference between the two. So again I'm going to go ahead and save this out. And let's go back into our channel box layer editor and I'm going to turn off the neon sign, and then we have two other layers. One is called mesh light, the other's called emissive light. So I'm going to go ahead and take both of these, and just move them so that they're fairly close to each other. So I'll have light that's pretty much the same from both of them. And then I'm going to go ahead and turn off mesh light. So I have a layer here called emissive light, and in that I have this sphere here, and that should be P sphere one. And so let's go ahead and put emission onto this little guy, shader. So I should have a material called AI standard seven, and so under emission we want to go ahead and just turn up the scale, just like we did before, and let's do a quick render. And as you can see, we get some light in the scene, but this really isn't illuminating the scene. So let's go ahead and keep this selected, and let's do a little trick here. So right now my slider only goes up to one, but we can push it a lot further than that. So if wanted to we could typ in a larger number. Say 50, and watch what happens. Now we get a slider that goes from zero to 100. So I'm going to go ahead and keep this at 50, and let's do another quick render and see what happens. So as you can see, with emissive light turned way up, we're starting to get a lot of noise, and that's one of the reasons why you want to use mesh lighting for these types of situations. So let's actually take a look at how mesh lighting would work. So I'm going to go ahead and save this out. I'm going to keep this image. And then I'm going to go over into my channel box layer editor and turn off emissive light and turn on that mesh light, and then select this object here. It should be called P sphere two. Now we can turn on mesh based lighting in the attribute editor. Now there are other ways of doing it. We can do it from the Arnold tab here, but probably the easiest way to do is just go over to the shape node for your object, and scroll down till you find Arnold, and in here we should have an Arnold translator at the very top, and if we change it to mesh light, that will turn this object into a light. Now we an change the color, we can change the intensity. In this case I'm going to turn up the intensity just to save time here. So I'm going to turn it up to 8,000, or we can change the exposure as well. And then we can change the decay. You want to make sure that you turn on light visible so that way the sphere is visible, and if we want to, we can turn up the number of samples. I'm just going to make it two just to give it a little bit more quality, and now once we have all of that, we can go ahead and just do another render, and here's the render, and as you can see, it's a lot better quality. In fact, if we fill it back to the other one you can see how it's much less noisy and much higher quality. Although it does take a little bit longer to render. It takes about maybe 50% longer. This was two minutes 36 versus 1:41. Now each of these techniques has its place. Mesh based lighting is better for a more traditional type of lighting, and emissive lighting is better when you want a shader to emit a little bit of light. So it's more of an effect, emissive lighting is. So let's go ahead and just do one more little thing here. I'm going to go ahead and go back to my layers and turn on that neon sign, and let's go ahead and do a render with both of those. So I'm going to go ahead and just do a very quick render here with emissive lighting and mesh based lighting, and there we go. Now we have a combination of emissive and mesh based lighting. So again, emissive lighting is more of an effect, but it's very easy to set up, and it's fairly fast to render. If you want a more global based traditional lighting, then go ahead and use mesh based lighting.