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Another popular form of lighting in Blender is called ambient occlusion. Now this is very similar to ambient lighting, but it adds in additional shading that gives it a much more realistic effect. So let's take a look at this scene. I have my standard cup and saucer, but I've removed all the textures so you can see the effect more clearly. Now let's go ahead and render this scene. And as you can see, there are no lights in the scene. Now ambient occlusion does not need a light to work.
It's kind of like ambient lighting, in that it's just an overall lighting in the scene. It's not a specific light. So we can get to ambient occlusion by going into our World panel and scrolling down to Ambient Occlusion. When I click that on, you'll notice how two panels light up: Ambient Occlusion and Gather. Let's just go ahead and do a quick render of ambient occlusion. Now as you can see, we get shading in the scene. That's because we're creating an overall ambient light.
Now ambient occlusion can be controlled. So we have a factor here, which is basically how much ambient lighting are we adding into this scene? We can either add or multiply against the existing background. So if we turn this down, say to 0.24, 0.25 or so, and do a quick render, you'll see that the overall ambient lighting has been reduced, and this is great if you're going to be using this in conjunction with other lights, so that you can have another light actually doing this specular of the diffuse, but you still have an overall ambient lighting in this scene.
I'm going to go ahead and turn this up to 1.00 again. Now the color of the ambience is based on the Ambient Color in the World setting. So right now it's black, so my darkest Ambient Color is going to be black. I can change this to any color I want. Usually we can change it to something like a dark gray to give it just a little bit of a brighter effect. Or if we want, we can tint this by adding in a color. So if I wanted to, for example, make this a green color, I could, and you'll see that now my overall ambient lighting is green.
I'm going to go ahead and turn that back down to a dark gray, something like that, and then let's just do one more render. Now another way to control how this effect looks is to go down to the Gather tab. By default, it's set to Raytrace, and so it uses ray tracing to create that overall ambient effect. Now ray tracing can be expensive in terms of render time. So we have a number of samples here that can control how much ray tracing it uses.
So with the default sample of 5, you can see how in this particular image we still get a little bit of graininess. But if we want to, we can turn that up. Let's say we bring it up to 10. We can render that again, and you can see how with more samples it smoothes out the graininess. But it also adds render time. So you have to find balance between acceptable graininess and the render time. So if we want, we can also do another type of gathering, and that's called Approximate.
And what this does is it just approximates the ambient occlusion effect, and sometimes this may just be good enough. If we do a render with the default settings here, you'll find that in this particular scene we get kind of a harsh effect. You'll see that the dark areas are very dark and the light areas are very light, but we can smooth that out by using sampling. So if I bring up my Sampling passes just to 1, you'll see that this moves out very nicely. But again, the more passes you have, the more render time.
But overall Approximate Gather is actually a little bit faster than ray tracing, at the expense of accuracy. Now I'm going to go ahead back to Raytrace and turn my samples down to 5. Now we have another way of doing ambient occlusion, and that's using what's called Environment Lighting. Now if I switch off ambient occlusion and turn on Environment Lightning, if I render that, you'll see I get pretty much the same effect, because really Environment Lightning is just another form of the ambient occlusion.
Now Environment Lightning pulls its color not from the Ambient color here, but from a selection that we have. By default it's at white, but we can use the Sky Color or the Sky Texture. So if I change this to Sky Color, I can turn on my Blend Sky here and give it a Horizon color, let's say a dark blue, and a Zenith color, let's say a very pale, blue, and what we can do now is use that to create my ambient occlusion.
So when I hit Render on this, the dark areas will be my Horizon color, the light areas will be my Zenith color, so you can see I get an overall tint of the scene. Now if I wanted to change this a lot, I could for example, change my Zenith color to a yellow or something like that, and then again render and you can see how it goes from yellow to blue. Now another way to do this is with a Sky Texture. Now we did this before in a previous lesson, but if we want to, we can go over to the Texture panel and add in a new texture.
By default, it's set to Clouds, but let's go ahead and pull in an image. We're going to pull in that same sky background that we used in the previous lesson. Now in order for this to show through, we need to change our Influence. So I'm going to go ahead and turn my Blend down to 0 and turn on Horizon and Zenith, and this will go ahead and make this bitmap show up as the background. Now if I go back to my World settings and make sure this is set to Paper Sky, I can use this to create my ambient lighting.
So if I turn this Environment Lightning on to Sky Texture, it will now derive my Environment Lighting from this bitmap texture. So if I hit Render, you'll see how this works. So with that render complete, you can see how it's pulling the colors from my sky. This is a great way to get very realistic lighting. You create a Sky texture, turn on Environment Lighting, and then you can balance this using the energy in the scene against the real lighting.
So just to refresh, ambient occlusion creates an overall ambient lighting, and we have two forms: we have ambient occlusion, which is just a simple color or if we want to have more complex lighting, we can use Environment Lighting.
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