14 Replies Latest reply on Feb 7, 2015 10:10 AM by Rick Gerard

    Motion Tracker Gone Wild?

    LexBurgerSupreme

      Hey guys!

       

      I'm fairly new to after effects cc and so far, it's been great for me BESIDES the motion tracker.

      The look I'm trying to portray is the typical "Text stays stationary, as the camera moves," look.

      No matter whether I use the AE motion tracker, OR mocha, it comes out the same.

      The text shifts/slide/moves a little bit as I preview the result.

      It just doesn't make since to me. I've tried other forums, I've researched this problem and it seems like nobody has it

      nor knows what I'm talking about.

       

      SOMEONE HELP!!!!

        • 1. Re: Motion Tracker Gone Wild?
          Mylenium Most Valuable Participant

          We can't know. We know nothing about your footage or other things.Trackers work based on mathematical and technical principles and have no magical powers. If they don't get you the results you want them to produce, you shot your stuff wrong in the first place. It's really as simple as that.

           

          Mylenium

          • 2. Re: Motion Tracker Gone Wild?
            LexBurgerSupreme Level 1

            How do assume I shot it wrong if you know nothing about it? 0.0

            What do you need to know about my footage in order to give me a right answer? As i said, I'm new to after effects.

            • 3. Re: Motion Tracker Gone Wild?
              Rick Gerard Adobe Community Professional & MVP

              I'm guessing that you are trying to track something that is too small and that your track is not accurate. If you apply tracking information to a layer it will precisely follow that tracking info. You need at least 100 pixels, 400 would be better in an area of detail that remains fairly constant to pull off a good track. In many cases you'll have to adjust a few of the frames manually as things shift. This applies to Mocha as well as the motion tracker in After Effects. If you are talking about camera tracking, then not all shots will accurately track. Motion Blur, compression, and unsuitable subject matter in the frame can foul up these tracks.

               

              Here is a sample of a track area that is way too small:

              Screen Shot 2015-02-02 at 7.07.48 AM.png

              The tracker is going to have a very hard time following the catch light in the eye.

               

              This tracker is going to work much better because the entire eye and surrounding area doesn't change much in the entire shot.

              Screen Shot 2015-02-02 at 7.08.23 AM.png

              There were 4 or 5 frames that needed to be tracked by hand when the dog blinked, but other than that the resulting track was nearly perfect the first time out. To make sure you have a good motion track or stabilize motion track you must go through the track a frame at a time after you're done and make sure that the attach point (moved in the top picture so you could see the catch light) is accurately tracking the point you want to capture.

              • 4. Re: Motion Tracker Gone Wild?
                LexBurgerSupreme Level 1

                Thank you Rick Gerard, for that reply!

                This is exactly what I'm talking about! And I have gone through manually, frame by frame, to make my track perfect, but, for some reason when I apply it to the null, and attach the text to the null, it still shifts as the camera moves. It just doesn't make any sense to me! :/

                I feel like maybe I'm doing something wrong? But, i keep thinking because I've tried it on so many different clips of footage, perhaps I just shoot crappy footage?

                • 5. Re: Motion Tracker Gone Wild?
                  Rick Gerard Adobe Community Professional & MVP

                  If you reveal your keyframes (press the U key) you'll see that the numbers for the track you choose and the position of the null will precisely match. The track is jittering because the track is off a pixel or two here and there. You can use expressions to smooth things out or delete some of the bad keyframes, but that's basically what you get.

                   

                  When I'm doing things like roto or attaching something to a tracked object I usually don't track, I stabilize the shot so the part I'm trying to attach something to doesn't move. Then I'll drag out some guide lines and make sure that the stabilizing is acceptable. I then add my layers. For example, an arrow and some text pointing to a detail. When I've got that part set up the way I want to have it setup I'll add a null to the project, then attach the null's position to the stabilized layer's anchor point with a simple expression created with the pickwhip. I'll then select my stabilized footage and the artwork and parent both layers to the null. This will put back the motion, keep everything completely editable, and, most importantly, make it very easy to make any changes or fixes to the project with a minimum of fuss.

                   

                  Here's a very quick tutorial I did a while ago showing the technique. Imagine the target and the pre-comp was just a single layer in a pre-comp...

                   

                  • 6. Re: Motion Tracker Gone Wild?
                    LexBurgerSupreme Level 1

                    Thank you very much for that!

                    Okay, so I uploaded a video of what its doing but I wanna clarify something first.

                    I know the footage was shot fast and crappy but, even with other footage, that isn't so bad and moves so rapidly, it does the same thing.

                    The text shifts as the footage moves.

                    Here, see for yourself:

                    Motion Tracking Problem! - YouTube

                    • 7. Re: Motion Tracker Gone Wild?
                      Rick Gerard Adobe Community Professional & MVP

                      The biggest problem with your shot is lens distortion. I've put together an ad-libbed tutorial showing one approach to the problem. If the upload doesn't  fail It should be up shortly.

                      This gave me some ideas for an in depth tutorial on motion tracking vs 3D camera tracking.... Hope this helps.

                      • 8. Re: Motion Tracker Gone Wild?
                        LexBurgerSupreme Level 1

                        OMG! That's awesome! That's what i was trying to do all along!

                        So the problem was my lens distortion? How does that come about?

                        And can you please explain the stabilize motion thing? I don't quite understand, I was a little loss.

                        So does this mean that I can just track motion and call it a day anymore? Every single time I have to do this? 0.0

                        • 9. Re: Motion Tracker Gone Wild?
                          Rick Gerard Adobe Community Professional & MVP

                          Every lens has distortion. Spend $40,000 for a wide angle cine lens and you'll have less, but you'll always have some. The wider the lens the more the distortion. Take a look at any uncorrected shot from a GoPro or other action camera.

                           

                          You can calibrate your lenses and build lens profiles to remove the distortion. Some software, like Syntheses will do this while camera tracking so that you can more accurately insert CGI elements into a scene.  Unfortunately there is no easy way to accurately calibrate video directly in AE. You can use Lightroom or Camera Raw to load up lens profiles for many different lenses but strictly inside AE you only have access to the lens compensation plug-in.

                           

                          If your video was shot with a consumer or even prosumer camcorder with a zoom lens then you can get yourself or make yourself a grid and then shoot it with the lens set all the way to wide angle and the camera lined up perfectly square to the grid, then apply the lens compensation plug-in and try and line things up the best you can. When you have removed the distortion you would then pre-compose or render a DI and use that corrected footage for your composite.

                           

                          If you are shooting with a DSLR and Lightroom or Camera Raw has a lens profile for your lens then you could export the original video to an image sequence and then use the lens profile to correct all of the images in the sequence before you start your composite.

                           

                          Do you have to do this all the time? No... it depends entirely on your shot and the object you want to insert into the scene. Because you were trying to insert text at the very edge of the camera pan and there is significant lens distortion in this shot you need to compensate for the changing perspective as the text moves through the shot. You would have had less float if you had attached the text right to the tracker point, but the scale issues would persist. If there were four points you could track where you wanted to insert your text then you could have used corner pin tracking to add the text. You could also have used Mocha to do the tracking. If you corrected most of the lens distortion in the shot before you started you might have been able to use AE's camera tracker. Every situation is different. The trick in the compositing business is known the easiest and fastest way to achieve acceptable results.

                          • 10. Re: Motion Tracker Gone Wild?
                            LexBurgerSupreme Level 1

                            Wow. I cant even lie, but,  that's a lot to swallow. And I tried mocha through a tutorial and when I copied it to the clipboard, it came out just the same. I feel like maybe I suck? I follow all tutorials and I feel like nothing works out for me. And how do you get rid of lens distortion? I posted this on another forum and someone said the same thing about lens distortion when I tried this same project on handheld footage.

                            • 11. Re: Motion Tracker Gone Wild?
                              LexBurgerSupreme Level 1

                              Then I see people do this on non-professional cameras like this:

                               

                              www.youtube.com/watch?v=S5ODJkLSdI8

                               

                              And I'm thinking "why the hell can't I?" Now I dont even know where to begin.

                              • 12. Re: Motion Tracker Gone Wild?
                                Rick Gerard Adobe Community Professional & MVP

                                Remember that I said about it depends on the shot?  The YouTube example in your previous post uses 3-D camera tracking and the lens is close to what is called "normal" rather than wide so the small perspective mismatch is hidden because the text is floating above the stairs. This lets you get away with stuff that you wouldn't be able to get away with if you had attached the text directly to the stairs.

                                 

                                In your shot your track is especially difficult because there's not much to track in the grass, your lense is very wide and image stabilization (most likely) and lens distortion have seriously effected the perspective, and I would bet that your track point is very far from the anchor point for your text layer.

                                 

                                Most of the time with a handheld shot and a medium or normal lens After Effects Camera tracker will do a fine job. The track will always be better if you compensate for lens distortion. The success of any composite shot depends on how suitable shot is to compositing.

                                • 13. Re: Motion Tracker Gone Wild?
                                  LexBurgerSupreme Level 1

                                  Well, can you show me a tutorial how to stabilize my shot and get rid of lense distortion? Because now I don't know what shots are acapable of what things. I'm so lost.

                                  • 14. Re: Motion Tracker Gone Wild?
                                    Rick Gerard Adobe Community Professional & MVP

                                    Do you mean a different shot? I have given you one approach to stabilizing your sample shot. I also posted an example showing how I stabilized a shot with a single track point and added a target that followed a girl playing the flute. That example used footage from an iPhone.

                                     

                                    There are tutorials about using the camera tracker to insert 3-D objects inside a shot. Lots of them.

                                     

                                    You use different techniques to work on different kinds of shots. I don't have a specific link to a tutorial on removing lens distortion from a shot. Actually, most of the time if you are just adding a text layer or placing some other element in a shot it is not necessary to remove the lens distortion.

                                     

                                    Why don't you upload a short shot that you want to add some element two, describe in detail what and where you want to place that element and I will see if I can point you to a solution.