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In this chapter, we are going to look at the basics of lighting in 3ds Max. Now before we get to lighting our actual flying logo scene, I want to spend a few minutes talking about how CG lighting works, and how it doesn't work. In other words, how is it different to the way lights work in the real world? So what I've got here is a very simple scene with some primitives, and I am going to drop an omni-directional light into this scene so that we can see how the basic lighting model or shading model works in 3D computer graphics.
So I'll go to the Create panel, and I'll go to the category of Lights. 3Ds Max, now by default, has Photometric lights as the default choice. We are going to be using Standard lights in this course. So I am going to choose Standard, and I am just going to make an Omni light and click in the view port. So I have just created on Omni light. And I will right-click to exit the Omni tool. Okay, so now you'll immediately see that things look kind of unusual and strange here.
I'll hit F4 to turn off the edges there. And so what you see here is I've got a light that's placed at an elevation of 0, or a Z position of 0. And it's illuminating those primitives, but it's not illuminating the ground plane. So this is the first thing where you'll notice that CG lighting is very different from real lighting. If I move this light up in the scene, ironically and paradoxically, as I move the light upward, I am illuminating the ground plane more.
So I will move it back down again. As I move it down, less light is shining on the ground plane. As I move it up, more light is shining on the ground plane. And this is exactly opposite of what you'd expect. Why is this happening? It's happening because the primary consideration is is this surface pointing towards the light or not? And when we move the light down, basically less and less of the surface is pointing towards the light. You can kind of see that in the Front Viewport, and this is where the ground plane is.
So as I move the light up, basically we're getting more of this surface is actually looking at the light, if you will. If I move this in the Top View, I will position it so that it's near this sphere. Move this around a little bit so you can see this a little bit better. Okay. So if we just look at this sphere here, that's probably a good example. What we are seeing here is that this part of the sphere here is pointing towards the light, and this part is pointing away from the light.
And this part here is pointing at right angles. And that's how the shading is calculated here. If a polygon face, or any part of a surface, is pointing towards the light, it's going to receive a lot of illumination. If it's pointing kind of partly away from the light, it will receive less illumination, period. And if it's pointing in the opposite direction, no illumination. And that's it. It's just based upon face angle. So if the surface is angled towards the light, it receives illumination.
So this is very different than lighting in the real world, because in the real world when you move a light towards something, the surfaces kind of become brighter, not dimmer. So that's the first thing that's really quite counterintuitive here. Next is the fact that there are no shadows in CG, by default. So in the real world, a shadow is the absence of light when light is blocked by an intervening surface.
Well, in CG that has to be calculated. We have to actually test to see where this object is in relation to the light and actually project a shadow onto a nearby surface. So Shadows, they don't come for free in CG, and they have to be calculated. So shadows need to be enabled if you want to see them. We will be covering all that in later movies in this chapter. But I just want you to know here now that shadows are not part of the equation by default, and they actually have to be enabled.
And you want to be judicious about this and only enable shadows where they are actually needed, and they are enabled on a per light basis. And then the last thing that's very different about CG lighting versus lighting in the real world is that, by default, light intensity does not diminish with distance in CG. So in the real world, as you shine a light somewhere, basically it's going to fall off over a distance, according to something called the Inverse Square Law for a point light source. The intensity falls off with the reciprocal of the square of the distance.
Well, basically what that means is if you have a light bulb, it's going to be much dimmer farther away and much brighter close to the light. Okay. Well, in CG that doesn't happen by default either. And I have got actually two spheres here that are lined up. So there is one here and one in the back here. And you will see they look identical. So in the real world, we would expect that this sphere would be brighter, and this sphere would be dimmer. But that is not the case in CG. If you want intensity to decay with distance, once again you have to turn that on and adjust it and tweak it.
So this is just to get you oriented around what CG lighting does and what it doesn't do, how it's different from the real world. If you have been used to using real lights in the real world, you are going to have to kind of relearn a lot of techniques in order to get good results in computer graphics.
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