You can use the Aim constraint to modify an object's orientation so that the object points to other objects. 
         
         To use the Aim constraint to orient objects:
         
         
            - Select an Aim constraint from the Asset browser’s Constraints folder and drag it into the Viewer window. 
                  - If you drag it into an empty area of the Viewer window, the Aim constraint template appears in the Constraint settings. 
 
                  - If you drag the constraint on top of an object, a context menu appears asking if you want to assign the object as one of the
                     constraint’s operators.  
                  
 
               
 
             
            - Assign the object that you want to aim to the Constrained object (child object) cell. 
 
            - Assign the objects that you want set as a target for the aimed object to the Source (parent object) cell. 
               
TipYou can have more the object divide its aim between multiple objects by Alt-dragging them to the resulting Source cells. 
                  
                 
             
            - Click Lock in the Constraint settings if you want to maintain the current offset between the source and target. 
 
            - Click Snap. 
 
            - Click Active to activate the constraint. 
 
         
         
         
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