The Reveal
            tool allows you to paint the contents of one or more source front images
            directly onto the result. You can also use the Reveal tool to copy source
            matte images onto the output matte. For example, if one source has
            a tree that you would like to include on the canvas, you can select
            the source with the tree and then paint it onto the result.
         
         To paint with a copy
            of the result or output matte image, use the Clone tool. See 
                     Clone.
         
         NoteIf changes are made
               upstream of the Paint node, revealed strokes are preserved. However,
               the strokes will reflect the “old” input unless
               you force an update by clicking the Update button or by pressing U. Updates are not performed automatically because
               they affect system performance.
            
         To
            reveal a front or matte input:
         
         
            - Select Reveal from the Paint Modes box
               (or press E).
               The Reveal Offset parameters
                  appear.
                
- Set the brush attributes. See 
                        Brush Attributes and Attribute Modes.
            
- In the Sources list, select the source
               you want to reveal. 
               NoteYou can reveal sources
                     that are marked as hidden in the Sources list. You will only be
                     able to view the strokes created with a source when you disable
                     Hide Strokes.
                   
- To limit the revealed sources to the
               areas delimited by their mattes, select an option in the Matte Source
               box.
            
- To display the source as an overlay of
               the result image, enable Overlay (Tab).
               You can apply transformations to the source before you apply strokes:
               
            
- Click and drag on the canvas to apply
               strokes that reveal the transformed contents of the selected source.