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This movie is going to review some fundamental concepts when working with CG lights in mental ray. There are two main types of light. We have direct lighting and indirect lighting. What direct lighting means is it's light that comes from a light source: rays of light coming from the sun, or a flashlight, or light in a room. Direct lights cast shadows when they encounter objects in the scene. Indirect lighting is the type of lighting that is caused when a ray of light from a direct light bounces off a surface and starts to encounter other surfaces in a room.
It's a type of ambient light. So I want to talk about direct lighting in this movie, and show you how some different types of direct lighting can be simulated. So I have a room model here, and this room was created by my brother Travis Keller for his design company, Silver Hammer Design and Construction. So he actually uses this to show off designs to clients. This is a room that he created. First, I want to show - I have a direct flight here, and this light is going to simulate a light source from outside of the room, and it's going to have shadows turned on for it.
You can see that the light is in the center of the room here, but if I do a render, you'll see that the light source comes from outside the room, and it's coming through the windows, and the shadows cast in the scene are created by the window frames. So if you remember, the only thing that affects the directional light is the rotation, not the position. So even though that this light source is in the center of the room, since it has shadows coming on, it's still coming from outside the room, and it's casting these shadows, and this is the affect that we see.
So here is an example of a direct light source from outside the room, maybe this is moonlighting or something like that. So I am going to store this image and close this. I am going to hide this light, and I have two point lights in here. These are candle lights. I'll show these by selecting them in the Outliner and doing Shift+H. And if I zoom in here, you can see that they are positioned above the candles, and again, they have shadows turned on. So I'll do a quick render. Then we can see that they're coming from a particular light source above the candle.
Now these lights are currently not visible in the scene. It's just the effect of the light that you are seeing. So it's casting shadows in all directions. If I store this image and compare it with the directional light, you can see the way this shadows are cast are affected by the light type. So the directional light, we have shadows that are cast, coming in through the windows, and they are very straight, because all the light beams of the directional light are parallel, whereas with the point light, you can see that the shadows are casts from a point, and they are going in all directions, so you can see how the back of the chair, its shadow sort of distorted this way, because the light beams are coming out in all directions.
So I am going to hide this, and I am going to show spotlight. In this case the spotlight is positioned here right in front of the picture, and I will do a quick render here, and we can see this kind of looks like a flashlight. It's casting lights, and the shadows are being distorted in this direction, so this another example of direct lighting. I am going to store that; you can compare it with a point light. You see how the different shapes of the shadows that are being cast is determined by the shape of the light itself.
Directional light, point light and spotlight. I'll store this and Ctrl+H to hide this light to turn it off; Shift+H to turn on the area light. If I go out of the room here, I can see that the area light is positioned above the room. It also has shadows turned on, and so it's coming through the skylights here in the ceiling, and if I do a render, we'll get an idea of how the shape of the light and shadows look as they are being cast from outside the room. In this light, in this case coming through the skylights, it does a good job of sort of simulating lighting coming from an overcast day, and this functions as a type of direct lighting, diffused lighting coming in.
So we can see how the area light affects the lighting in the room. It's casting shadows, it has a position in 3D space, it's coming through these Windows, and so this is another example of direct lighting. Direct lighting has a light source, and it creates cast shadows. Those are the most important concepts to understand when you're dealing with direct lighting. So when you're coming up with a lighting scenario for a scene, the first thing you want to think about is what type of lighting am I creating, what is the light source, what kind of shadows does it create, and how can I simulate those shadows using the different light types?
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