Stacking Order

The stacking order refers to the placement of the objects in a stack. Objects at the bottom of the stack are covered by objects at the top of the stack.

Each object you create occupies its own position in the operator and is represented by a name in the Timeline and the Workspace panel. As you draw, make selections or masks, or add effects, each new object is added to the active viewport in front of the other objects. You can change the stacking order of the objects in the operator at any time, changing the appearance of the objects and their effects on the underlying clip or still image.

You can change the order of objects, moving them backward or forward one level at a time, or moving them directly to the front or to the back of the image.

To change the order of overlapping objects:

1. Select the object whose stacking order you want to change.
2. From the Object menu, choose one of the following.
   
   

   Choose:	To:
   Bring to Front	Move the object in front of all the other objects in the operator. In the Timeline list, the object moves to the top of the list.
   Bring Forward	Move the object forward one level. In the Timeline list, the object moves up one position.
   Send to Back	Move the object all the way behind the other objects in the operator. In the Timeline list, the object moves to the end of the list.
   Send Backward	Move the object back one level. In the Timeline list, the object moves down one position.

   
   
   

Note: You can also change the position of objects by dragging them up or down in the Workspace panel or Timeline list. For more information, see Changing the Order of Objects or Layers.

Stacking and Selections

Selections act on objects above them in the stacking order until another selection is encountered. By default, the combination mode is Replace.

If you create a selection on top of an existing selection, the new selection becomes the active selection. Newly created effect operators only apply to the active selection.

You can still add a filter to the original selection. To do this, add the filter to the top of the stack, then drag it down to the appropriate position above the first selection.

You can combine multiple selections using the Add, Subtract, and Intersect modes. For more information, see Adding, Subtracting, and Intersecting Selections.

Stacking and Masks

Masks act on a layer's alpha channel making the area outside of the mask transparent. In this area, objects below the mask in the stacking order are transparent; objects above the mask in the stacking order may or may not be transparent depending on their own alpha information. By default, the mask mode is Replace.

For example, if you draw an ellipse without an alpha channel (only RGB), then the shape will not change the layer's transparency and therefore will not be visible outside the mask. If you draw an ellipse with RGB and alpha channels (RGBA), then the shape "overwrites" the mask's alpha information, and the ellipse is visible.

You can combine multiple masks using the Add, Subtract, and Intersect modes. For more information, see Combining Masks.