Setting Up Render Layers
You now need to separate Jim from his shadow so you can control the shadows separately in the compositor. This is simple enough because the Render Layers feature allows you to separate elements in different layers and composite them later.
1. First, you need Jim and the floor to exist in different layers of the scene. If you’ve followed this chapter’s instructions to the letter, you should have Jim in one layer and his rig in the one below (layer number 11, in the bottom row). Now, select the floor, press M, and select another layer. Jim’s model could be in the first layer, while the floor could be in the second one.
Tip
While in Object Mode, you can select the visible layers in the scene on the 3D View header. Press Shift while you left click several layers to be able to see more than one layer at a time.
2. Take the sun lamp and move it to yet another layer using the same method (for example, the last layer of the first layers group).
3. Go to the Render Layers tab in the Properties Editor (see Figure 14.5).
Figure 14.5 The Render Layers tab, where you can set those elements of the scene that will be rendered separately
Note
In the Render Layers tab, you can create new Render Layers and define which layers of the scene are going to be rendered in that specific Render Layer. Also, in the Passes panel you can select the passes (channels) of that layer that will be rendered. For example, you can render Ambient Occlusion, Diffuse, Specular, etc., and these passes would become outputs in the Render Layer node so you can work with them in the compositor. For example, a Specular pass would give you the areas of the scene that are shiny, which can be very useful for creating the appearance of glare in the scene that could be mixed into the original render. As you can see, there are quite a few possibilities, but as this is just an introduction, you’ll use only the basics for now.
4. Create two Render Layers and name them Jim and Floor Shadows. For both of them, in the Layer panel, select the layers that should be rendered for each Render Layer under the Layer section. Keep in mind that if you want the light to affect the elements in both Render Layers, you need to enable the sun lamp layer in both of them and that’s why, a moment ago, you moved the sun lamp to the last layer in the first layers group (see Figure 14.6).
5. If you launch a render right now, you’ll see the sky color behind Jim and his shadow. Go to the Render tab of the Properties Editor and, in the Shading panel, set the Alpha to Transparent. Now the background of the renders will be transparent, allowing you to insert your footage there.