Using Depth Sort

When a project includes multiple layers, the layers appear in both the working area and in the rendered project based on their position in the Layers palette with layers at the top of the Layers palette appearing above any lower layers that are overlapped. This is the default behavior, but using the Translate Layer tool (1) while holding down the Alt/Opt key causes the layer to move backward along the Z-axis.

The relative position along the Z-axis of the various layers is clearly visible if you change the view to the top or side using the View, Direction, Top menu command. The layers will be a straight line when viewed from this perspective unless the camera has been tilted, but you still will be able to tell that the layers are different distances from the front camera.

If you open the Project Settings dialog box, found in the File menu, you’ll see that there is an option to Sort Layers by Depth. If this option is enabled, then the layer content is displayed based on its depth from the camera. Next to the Sort Layers by Depth is another option to Sort Layers by Distance. This option is only available if the Sort Layers by Depth option is enabled, and it determines the layer’s stacking order based on the layer’s origin from the camera. This is helpful when the layers are rotating.

To layer content by depth, follow these steps:

1.	Open the Desert scene.anme file from the Chapter 25 folder on the CD. This file includes four layers for the cactus, the rock, the sun, and the background. Notice in Figure 25.7 that the cactus is displayed in front of the rock, the sun, and the background because it is positioned at the top of the Layers palette. Figure 25.7. The top layer appears in front of the other layers. [View full size image]
2.	Select the background layer in the Layers palette and choose the Translate Layer tool (1). Then hold down the Shift key and drag in the working area to push the background layer content back into the scene. The background will get smaller as it is pushed backward.
3.	Select the cactus layer in the Layers palette, and with the Translate Layer tool (1), hold down the Shift key and drag in the working area to pull the cactus layer content forward. The background will get larger as it is pulled forward. Use the Scale Layer tool (2) to resize the cactus layer after moving it forward.
4.	Repeat step 3 for the rock layer, but move it farther forward than the cactus layer. Even though the rock layer is closer to the camera than the cactus, the cactus is still on top of the rock.
5.	Select each layer and with the Rotate Layer X tool, drag upward in the working area to tilt the layer slightly. Then choose the View, Direction, Top menu command. Notice how each layer is at a different distance from the camera, as shown in Figure 25.8. Figure 25.8. The Top view shows the distance of each layer from the camera. [View full size image]
6.	Select the File, Project Settings menu command and enable the Sort Layers by Depth option and close the Project Settings dialog box. Select the View, Direction, Camera menu command to switch back to the camera view. Notice that the depth of each layer is controlling its visibility, making the rock appear in front of the cactus now, as shown in Figure 25.9. Figure 25.9. The distance from the camera controls which layers are visible. [View full size image]