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mental ray has a special Ambient Occlusion texture which can be used to add additional shadowing within a shader network. As you may know, Ambient Occlusion passes can be created with the render pass section when you're doing a render. So we go to Render > Render Settings under Passes. You can actually create an overall pass that adds Ambient Occlusion shadow into everything in this scene. But in this case I don't want to do that. What I want to do is I want to add just a little bit of extra shadow and detail to the skin shader applied to my old man character, because as you can see I have a nice skin effect going.
However, it looks a little flat, and it looks a little plastic. You can see especially in the ear, this looks kind of very flat to me. I'm losing some of the detail. I'm not getting as much of the detail here in the wrinkles that I'd like to have. So one solution is to use an Ambient Occlusion texture and connect it to the skin shader network that I have going already. I'd like to show you how to do that. So I'm going to store this image, so that we can compare it with subsequent renders and I'll minimize the Render View. Let's take a look at this skin network. This is the misss_fast_skin_maya2 shader that's been applied to the old man.
I'm going to rename this skinShader to make our lives easier. There we go. I've experimented with several ways of doing this and I've found that for the types of renders that I like to do, I like to add the Ambient Occlusion texture to the Overall Color channel of my skin shader. You can try adding it to the Ambient network, but that's going to start to brighten the overall look of the surface. So I use Overall Color. The way this shader works is you have a Diffuse Color and right now I have a texture that is creating like that freckles and that kind of stuff on the surface of the skin and that it's Diffuse Weight that determines the strength of the Diffuse Color within the network.
Then, on top of this is an Overall Color which you can use as a general volume knob. If I start to pull this down, you can see how it's lowering the coloring of the entire shader itself. Let's set this back up to white and I'll click on the texture icon to the right of the slider. This pulls up the Create Render Node window and I'm going to go to mental ray > Textures and I'll click on mib_amb_occlusions. This is the Ambient Occlusion texture. This connects it to the network, and I just need to adjust a few settings here.
For one thing the Samples setting will increase the quality and remove some of the graininess that comes with the shadowing found in the shader. So I'm going to set this to 32. Let's just create the rendering with these settings and see what we get. So here's our resulting render. Let me store this and we can compare it with the earlier one. So you can see how the Ambient Occlusion is adding shadowing in the ears here on these surfaces within the eye and the wrinkles. However, it's a little bit strong and there's a few things we can do to sort of tone this down a bit.
For one thing, the blackness of the shadowing I think is sort of at odds with the nice red color that we're getting out of the SubSurface scattering effect. They're kind of working against each other. That's easy to fix. I'll just click on the Dark color here in the Ambient Occlusion Texture node and raise this to maybe like a Dark Red, so that will help to be a little bit more in harmony with the SubSurface Scattering effect that we already have going. The other setting that I want to change is the Max Distance. By default, this is set to 0. As it calculates the shadowing effect, it's going to look at each object that has the shader applied and see what's close to it, and if this is set to 0, it's just going to keep looking almost to an infinite distance.
So I actually want to raise the Max Distance a little bit. I'll set this to 5. So it's like 5 units to see how far it needs to look. By increasing this will remove some of the problems where I like the proximity of the monocle to the skin is causing a little bit too much shadowing. So let's see how this looks when I create a render. Now, you can compare it. That's starting to look a lot better. It's a little bit more subtle and subtlety is actually what I'm going for here. So here's without Ambient Occlusion, here's with the default settings, and then this is after just a little bit of tweaking.
So that's a basic idea. If I wanted to make a few more adjustments, I can increase the softness of the shadowing by increasing the spread or the tightness of the shadowing by decreasing the Spread, and again I can play with the Max Distance to see how far mental ray has to look in this scene to see the closeness of other objects before it starts adding shadowing.
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