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Ambient occlusion is a rendering effect that's designed to enhance realism, by creating a darker area in surfaces that are close together. And the idea here is that ambient light, or indirect illumination, doesn't reach into the cracks and crevices between things very well. And so you get what are known as contact shadows, where it's darker in those crackers. Or where two surfaces are really close together. That's what ambient occlusion is all about.
And we're going to do that in this exercise, but we're going to do it in a kind of special customized way. Because there are many ways of adding ambient occlusion. And one is directly in the arch and design material. Let's take a quick look at that. Open the Material Editor. And we want to go to our, watch body material. Bring that over, kind of separate from everything. And to double-click on it. Get it's parameters up. And if you open up Special Effects, you'll see Ambient Occlusion. If we enable this, then the final gather indirect illumination will be blocked, based upon this distances.
If two surfaces are closer together than ten centimeters in this case, then they will receive less final gather information. So, it will be darker there. And the darkness, or the amount of blocking ,is controlled by the shadow color. Normally, if you're going to use this, you would set that shadow color to black, to enhance that effect to its maximum, and set the max distance to something reasonable like a centimeter or whatever. However, in this case I want to create what's called a Dirt Map.
And I can use ambient occlusion, to block not just the indirect illumination from final gather, but also the direct illumination from lights, and also the highlights and reflections. So I'm going to disable ambient occlusion within the arch and design material, and I'm going to create the effect from scratch. In your Map section here, in the Material Map Browser, you'll see there's a Mental Ray Map section, and here we have Ambient / Reflective occlusion.
Drag that over to create it, and we want to connect it to the Diffuse Color Map. So, click and drag over to diffuse color map. We go up to the top of our material parameters, you will see there's a lower case m here, next to the diffuse color swatch. That lower case m indicates that something's connected there, but it's not currently active. We need to activate it, scroll down to the bottom, and open up General Maps. And enable Diffuse Color, and now that ambient reflecting occlusion map node is actually affecting the diffuse color.
Okay, so, now to make this a good demonstration, I'm going to change a bunch of parameters. I'm going to change the diffuse level to one, increase that up to its maximum. And just temporally set the reflectivity down to zero. So we can really see the ambient occlusion effect in action. I'll double-click on that node, and I'm going to change these colors. Normally we would just leave these at white and black. I'm going to change these to really extreme colors, so that we can see what's going on with the ambient occlusion effect. I'll set the bright color to bright red.
And I'll set the dark color to bright green. I'll also want to adjust these parameters here. The spread controls the evenness of the effect. If want it to be perfectly even across the surface, we'll set the spread to one, and then the max distance is the size of the effect. I want to set this to a value of one centimeter, here just for demonstration purposes. We'll come back in here and change that again later. All right and finally, just to speed things up a little bit, I'm going to go into Render Setup, and just turn off Final Gather. And tha'll also illustrate that the ambient occlusion effect can exist independent of final gatherer or indirect illumination.
Okay, so, final gather's turned off. I've got really extreme settings here, for the ambient occlusion color, so we can do a test render. Okay, that's a really good illustration of what final gather does. In areas where surfaces are close together, we have a different color. Cool. So now we're going to set this to colors and values that work with our particular scene. I'll re-enable Final Gather and close that Render Setup window. Set the dark color back down to black. No green, no red, no blue. The bright color we want to be, the diffuse color, which is the orange.
So, we'll give it a little bit of green, half green and no blue. So that's the orange color for the diffuse. And then the max distance, I'll set it to a value of 0.3 centimeters. Great. And then, back in the watch body material, double-click on that. Set our diffuse level back to 0.3, and our reflectivity back up to one. And now we're going to be blocking all the light that's reaching the diffuse component. But to give it and even more of an effect, we can also block the reflections and highlights.
To do that, I'll make another ambient occlusion node. Hold down Shift and drag to create a copy, and then, let's just organize our scene here a little bit. Connect this ambient occlusion node, to the reflection color map. And then double click-it. Because we don't want it to be the same color. Remember we want the reflection color to be a little bit less saturated. Go into that bright color swatch. And bring the saturation down a bit to, about 0.9 or so. Maybe a little bit less. 0.8 something.
0.88 or so. Okay, so we've made all those changes. We've connected two ambient occlusion nodes, one to the diffuse color, one to the reflection color. We've got a max distance of 0.03 centimeters, and a spread of one on both, and, we're going to do a test render. Okay. That's looking all right. We've added the ambient occlusion effect, and now we've got a little bit more defined darkness in between the surfaces of things. And that's going to enhance the realism of our final rendering.
And that wraps up our chapter on materials, or product shot.
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