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Lighting and Rendering with mental ray in Maya with Eric Keller shows how to master practical mental ray techniques for rendering models created in Maya. This course walks through the most efficient and innovative mental ray techniques, including direct versus indirect lighting methods, creating different types of shadows, using the new ShadowMap camera, and reusing shadow and final gathering maps. A chapter on optimizing render times and enhancing render quality is also included. Exercise files are included with the course.
Area lights have the interesting property that sets them apart from other types of lights, in that they can actually be made visible in the scene. So you can actually see the light itself. So, I'm going to create an area light to demonstrate this principle. I'm going to click on the Area Light icon, and here it is in the outliner. So, I'll pull this up and scale it up a bit. So, a few things I want to do is I want to set the Decay Rate to Linear.
I'm going to set this to 8, so it's nice, and we have a decent intensity there. I want to turn on Ray Trace Shadows. Then in the mental ray Area Light section, I'm going to do Use Light Shape. So, I'm going to rotate this around so that it's facing the painting here on the wall.
Let's see how this looks when we render it. So, here we can see some of the effect coming out of that rectangular shape of the Area Light, and it's shining this way. So, I'm actually going to increase that Intensity, maybe even double it, and do another render. Now we're getting something a little bit brighter. So, now if I actually want to see this light in the room, I can scroll down to the Use Light Shape settings, and I can turn on Visible, so now when I do a render, we'll actually see the rectangular shape of the light.
There it is, this gray area right here. As I increase the intensity, I'm going to bring this up to - double it again, and just render this region, and start to see that it becomes brighter along with the light itself. Now, where this gets actually interesting is I can actually change the shape of the light. So, in other words, I have several choices here. I can set this to a spherical shape.
Now we can see how this light looks as a sphere. I might shrink this down a little bit, and create another render. You're going to see a couple of different things. For one thing, now the light is actually being cast from within a spherical volume. So, unlike a point light, which casts a light from an infinitely small point in space, we get light cast in all directions, but from within the spherical volume. That means that the shadows are nice and soft, just like we would expect with an area light, but it's also going in all directions.
There is also a Shape Intensity here. So, if I want to make the brightness of this shape more intense but not affect the intensity of the light that it creates, I can pump this. I'll try a setting of 2. I'm just going to render this region right here. We shouldn't see any change in the light cast on the walls, but you can see how the intensity is a little bit higher. So, as an experiment, I can try setting this to Cylinder.
I'm going to make this a bit more intense, maybe set it up to 4, and scale it down, and scale the shape this way, and move this over to match the position of the light fixture, near the light fixture of the painting. So, I'll scale this down a little bit, and actually place it here.
So now, it's actually going to act as part of this light fixture. The only thing I don't want is I don't want the geometry from inside the light to actually cast shadows or affect the light, maybe just the light casing.
So what I can do is I can select this and just hide it, because we're not going to see that anyway. So, now we can just have this acting as a light bulb from within the light fixture. So, let's do a test render and see how that looks from an angle like this where we can actually see the light in there. Obviously, the light is fairly grainy, because this is an area light. So, I'm going to have to increase the samples on the light itself to get rid of some of that graininess. But as a test render, we can see how this is starting to behave.
But now we can actually see the light inside the fixture itself, without having to create any extra geometry or shaders. So, in some instances, this can be very helpful for creating realistic lighting. Another way I could use this is I could create an area light and set its shape to spherical and place it inside each one of these globes.
I'll just do one here as an example. Once you create the light and establish its settings, of course, you can just duplicate it, and move it around, so that it appears within here. So, I have this turned on here. I'm going to set the Intensity up to 16, and the Decay to Linear, and turn on Ray Trace Shadows.
Now that I have this in here, I'm going to turn on Visible. Let's hide this other area light, the one for the painting, so we can just see this one. We'll start to see how this casts light in the scene. You can see that shadows are being created by the chandelier fixture, shedding light in all directions. So you can see the shadows of the chairs, the candlesticks on the table. Once again, I can reduce the graininess just by increasing the high Sample Limit.
We'll start to see less grainy appearance there. Of course, I've got something funky going on here. I'm going to increase the Shape Intensity. Let's set this up to 8, and see if that improves the look of the light. It looks like an actual light bulb is inside the globe there.
If you were using another type of light, such as a point light, or something like that, a type of light that doesn't have this visibility feature, what you'd have to do is you'd have to find a way, using geometry or a shader applied to geometry, to sort of simulate this light bulb effect being visible within the light fixture. That's certainly fine; there are definitely reasons for doing that. But this is a nice option that gives you another alternative for creating different lighting effects.
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