In this recipe, we'll see the properties and the settings of the World window in Cycles.
The main characteristic of the Cycles World is that it can emit light, so it practically behaves as a light source. Actually, its effect is the famous "Global Illumination" effect.
As in Blender Internal, it is considered as a virtual dome at a large distance from the camera and never touching the scene's objects. Nothing in the 3D scene can affect the World. Actually, only the World can emit light on the scene and on the objects.
start_04.blend
file and go to the World window under the Properties panel to the right of the interface. This is where we see the usual Use Nodes button under the Surface tab.R 0.179
, G 0.152
, and B 0.047
and save the file as start_05.blend
.Note that both the intensity as well as the general color graduation of the World are driven by this color. To have more light, just move the Value slider (the vertical one) towards a whiter hue. To give a general color mood to the scene, pick a color inside the wheel. This will affect all of the scene's illumination but will show mainly in the shadows, as shown in the following screenshot:
However, to have access to all the options for the World, we have to initialize it as a node system:
Also, for the World, the default material is simply made up of two nodes: a Background node connected to a World Output node. In the Background node, there are two setting options: the Color box and the Strength slider, both of which are quite self-explanatory.
Note that you can also modify the incoming direction of the light, that is, the location of the sun, by rotating the sphere icon inside the node interface.
start_06.blend
.texture
folder and load the Barce_Rooftop_C_3k.hdr
image (a free high dynamic range image licensed under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 License from the sIBL Archive http://www.hdrlabs.com/sibl/archive.html)..hdr
image assigned to the World material. Actually, you can also see the image as a background in the Rendered preview. You can also rotate the viewport and watch the background texture, "pinned" to the World coordinates, rotate accordingly in real time.start_07.blend
.But now, let's imagine a case in which we want to assign a texture to the World material and use it for the general lighting of the scene, but we don't want it to show in the background of the render. That is, for example, we are using the hdr
image to light the spheroid and the plane, but we want the two objects rendered on a uniform blue background, then how to do it? This is how we do it:
But the simplest way to render the two objects on a uniform blue background is to use a Light Path node:
R 0.023
, G 0.083
, and B 0.179
.hdr
image connected to the first Background node, but they appear on a "sky" that is colored as set in the Color box of the second Background node:start_08.blend
.To better explain this "trick", let's say we just created two different World materials: the first one with the texture and the second one with a plain light blue color (this is not literally true, actually the material is just one containing the nodes of both the "ideally" different worlds).
We mixed these two materials by using the Mix Shader node. The upper green socket is considered equal to a value of 0.000
, while the bottom green socket is considered as a value of 1.000
. As the name itself suggests, the Light Path node can set the path for the rays of light that, if you remember, are shot from the camera. Is Camera Ray means that only the rays directly shot from the camera have a value of 1.000
, that is, not the reflected ones, or the transmitted ones, or whatever, which instead have a value of 0.000
.
So, because the textured world is connected to a socket equal to the value 0.000
, we don't see it directly as a background but only see its effect on the objects lit from the reflected light or from the hdr
image. The blue sky world that is connected to the value 1.000
input socket instead shows as a background because the light rays shot from the camera directly hit the sky.
Just after the Surface tab, in the World window, there is the Ambient Occlusion (AO) tab. AO is a lighting method used to emphasize the shapes or the details of a surface, based on how much a point on that surface is occluded by the nearby surfaces. Although not exactly the same thing, AO can replace, in some cases, the Global Illumination effect. For example, to render interiors having fast and noise-free results, AO is a cheap way to get an effect that looks a bit like indirect lighting.
There is a checkbox to enable AO along with the following two sliders:
The Ambient Occlusion feature is only applied to the Diffuse BSDF component of a material. Glossy or Transmission BSDF components are not affected. Instead, the transparency of a surface is taken into account. For example, a half transparent surface will only half occlude the other surfaces.
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