Connect shader nodes to process ambient occlusion.
- [Instructor] In this movie, we'll look at using the Ambient Occlusion node and shading network in combination with other nodes to provide different effects. Namely, we'll combine the occlusion and noise to give a nice pattern for the base color here. We'll also use another occlusion node to modulate the roughness so that the more recessed areas will be rougher and therefore less reflective. In the Node Editor, I want to multiply the diffuse occlusion with the simplex noise texture and of course I could do that with Amaya Node such as multiply divide, but just for fun and experience, let's create an Arnold Multiply node.
Click in the Node Editor to deselect all nodes and press the Tab key in the search box that pops up. Type in "AI Multiply" and soon as you get to AIMU or so, you'll see AI Multiply. Select it and it's created. Let's connect it's output to the base color. Click and drag from the output to the base color. Let's connect the Diffuse Occlusion to the AI Multiply.
Click on the output for Diffuse Occlusion from the pop up menu, choose Out Color, Out Color. And in AI, multiply one, click on it's input. Choose Other and then click Input One. Now that connection's been made. Do the same for Simplex Noise. Click on the output. And choose Out Color, Out Color. Click and hold on AI multiply one input and choose Other Input Two.
And we can display the connected mode for AI Multiply. Just select it and press Two. Very good. We've got those connections made and now our diffuse color is being multiplied with this existing noise map. And that's giving a very interesting effect. We can enhance this by modulating the shininess or roughness. So let's go back to our AI Surface Material. And change this back into a metal look.
Our base weight is set to one. Let's bring Metalness up to one. And then we've got the specular weight. Bring that up as well to one and the roughness, a value of 0.2 and that's what it would look like if we did not modulate the roughness. We just set it all to be the same amount of roughness. Go back to the Node Editor and select the Diffuse Occlusion Node and make a duplicate.
Control D. Now you've got a duplicate AI Ambient Occlusion Node. Select it, and in the Attribute Editor, rename it. Call it Roughness Occlusion. We want to connect that to the roughness of the AI standard surface. Click on it's output and choose Out Color. But this time we'll want to choose one of the color components rather than the RGB output. Let's choose Out Color G and the reason we're doing this is because we're setting this to the roughness parameter which is a floating point and does not have an RGB input.
So choose Out Color G, and in the AI Standard Surface input, click and choose Other and we want to connect to Specular Roughness. So just select that, with the Occlusion Node connected to the roughness, we're getting some kind of interesting effect with the specular highlights, but it's actually the opposite of what we want. We want the areas in the recesses or crevices to be less reflective which means we want them to be rougher.
But in our diffuse component here, remember that the recessed areas are black so let's go over to Roughness Occlusion and investigate. In the Ambient Occlusion Node, we see a white and black color. The black color controls the strength of roughness in the recessed areas. And the white color controls the strength of roughness in the open areas. So we want the open areas to be very shiny relative to the recessed areas.
So to make the open areas more shiny, we can reduce their roughness and bring that down. If we bring it all the way down, we get perfect mirror reflections. And then of course, if we want the recessed areas to be rougher, we'll increase the black slider and with the maximum at white, we've now reversed the effect. So the recessed areas are the most rough and the open areas are the least rough, If we wanted to increase the roughness over all, we could bring the white amount up a little bit, or if we wanted to decrease the roughness over all, to make everything more shiny, we could bring the black amount down a little bit.
I'm going to make everything a little bit rougher. So click on the white color sample and give it a value of 0.2. Finally, we can make the whole thing a little bit darker by going back to AI Standard Surface and reducing the base weight down to .5 which will reduce the Diffuse component but preserve the shiny highlights because our metalness is set to a value of one. And that's how to use Ambient Occlusion in a shading network to modulate the base color and the roughness of an AI standard surface material.
- Arnold rendering concepts
- Lighting with Maya and Arnold lights
- Controlling exposure
- Filtering light with Gobo
- Light attenuation with Decay
- Image-based lighting with Skydome
- Exterior daylight with Physical Sky
- Arnold Standard Surface material attributes
- Mapping material attributes
- Rendering refractions
- Mesh subdivision and displacement at render time
- Shading effects such as ambient occlusion and vertex color
- Camera effects such as fisheye and depth of field
- Animation image sequence rendering