8 Replies Latest reply on May 11, 2013 9:11 AM by Lwheels07

    Rotoscoping versus masking


      I have a scene that am working on. It's the interior of an airplane and I need to replace what is currently being seen outside the airplane window. In the scene passengers arms are in constant motion across the window. I am pretty sure I can use a mask and change the shape on frame to frame basis, but I was thinking about rotobrushing since those tools seem to be able to create an outline pretty quick with just minor fixes between the frame. However rotobrushing/rotoscoping seems to be for cutting objects out of the overall image an to be used within another. What I need it to do is to exclude the window so I can put a different background in. I am pretty new AE and rotoscoping in general so I am not sure this is correct way to use these tools. Most/all of the tutorials focus on removing the roto object from the image not excluding/removing it. So is this the correct approach? Or is there a better way. Any suggestions will be much appreciated



        • 1. Re: Rotoscoping versus masking
          Mylenium Most Valuable Participant

          The "better" approach would have been green screen and keying. Beyond that you seem mightily confused. Masking is rotoscoping, too. Rotoscoping generally refers to all manual techniques to isolate objects in a frame, whether that's masking with shape paths, conventional painting, AE's Rotobrush or a million other workflows based on tracking, effects, mattes. Which one might work best for you nobody can tell, since we haven't seen your footage. That aside it's inherent that you will need to spend some time with this and look up some tutorials. Your problem is not Rotobrush, but to be candid the problem is that you don't have the slightest clue on how to deal with transparencies/ mattes/ channel operations to mutually mask out layers by duplicating, pre-composing and so on. You are looking for a simple one step solution that usualyl doesn't exist for this kind of work.



          • 2. Re: Rotoscoping versus masking
            Rick Gerard Adobe Community Professional & MVP

            If you want to use Rotobrush to eliminate hand in front of the window it would probably be easier to select the window instead of the hand and then invert the mask. There are several ways to do this. You can use the masked layer for a track matte for the original footage. You can use levels to invert the output of the alpha channel. You can use set matte. There are a bunch of techniques that you can use.


            If you post even a single frame of your footage showing a hand in front of a window it would be very easy to have us show you a basic setup.

            • 3. Re: Rotoscoping versus masking
              Lwheels07 Level 1



              Yes you are correct I am basically an editor/director with a vague notion of compositing and effects. Unfortunately I am also a person with very little time or dollar resources working towards a deadline, so you are correct I am looking for the most direct route. I believe I can just create mask go frame by frame and remove the unwanted background, however while experimenting with the rotobrush I noticed it does real good job of identifing frame boundaries. What I was having of problem with was understanding how to invert the cutout that was created when I rotobrush the object, which is a simply option when you use masks.

              • 4. Re: Rotoscoping versus masking
                Lwheels07 Level 1



                I have atteched to images. My other problem is the camera moves whcih changes the position of the window. So I tried tracking the frame of the window, then I created a new solid layer and attched the motion track to it. With the new layer selected I created a mask, however when I inverted the mast nothing happened -- any help would be most kind.


                Airplane 1.jpgAirplane 2.jpg

                • 5. Re: Rotoscoping versus masking
                  Klaus_Brandenburg Level 2

                  If the camera is steady you can imply mask out the window. Then duplicate your video layer, invert the mask, extend it, apply and extract key (should work just fine) and maybe a matte chocker. This should give you a good enough result.

                  • 6. Re: Rotoscoping versus masking
                    Rick Gerard Adobe Community Professional & MVP

                    Use Roto Brush on the window like this:

                    Screen Shot 2013-05-11 at 8.51.55 AM.png

                    Invert the foreground and background like this:


                    Screen Shot 2013-05-11 at 8.54.41 AM.png

                    I can tell from your screenshots that the camera is moving. This is a perfect situation to use Roto Brush. You may need to apply other matte tools and work on some light wrap but that's another lesson.


                    You could also use Mocha to track the window and make a mask but, if your original footage is higher quality than your screenshots, rotobrush should do a fine job.

                    • 7. Re: Rotoscoping versus masking
                      Lwheels07 Level 1

                      Looks great i will give it a try

                      • 8. Re: Rotoscoping versus masking
                        Lwheels07 Level 1

                        Thanks for the help!