Having trouble with a simple(?) track in Mocha for AE

JWA2014
JWA2014 Website User Posts: 6

Hi all,

     I'm trying to learn how to track and key better. I'm having some trouble with one or two shots in particular but the one that is giving me the most trouble is the clip titled "painting"(top of the list) here:

http://www.hollywoodcamerawork.us/trackingplates.html

After masking out the lady's arm and cloth I got better results but still at some point the track starts to move off of the board.

Have any of you guys taken a shot at this one before? I would love some tips on it and maybe some advice on how you were able to pull the track off on that shot. 

Thanks so much!

 

Comments

  • AxelWilkinson
    AxelWilkinson Staff Administrator, Imerge Beta Tester, HitFilm Beta Tester Posts: 5,250 Staff
    edited October 2014

     Make sure you start form the middle, where you can see the entire board, including the edges, but it is as close to camera as you can get.  Then track both directions from there.  Set up your tracking spline just outside of the edges of the board, so that a tiny bit outside the board is included in the spline.  Then mask out for the arm and you should be good.

  • JWA2014
    JWA2014 Website User Posts: 6

    Hi Axel,

     

         Thanks. I actually tried tracking from the middle and doing exactly the same thing you said. But, for some odd reason the track just doesn't stay. Eventually it veers off. I don't understand what I'm doing wrong. I've even tried masking off the little blue diamond markers to see if that's causing the issue I'm getting but it didn't help much. 

  • AxelWilkinson
    AxelWilkinson Staff Administrator, Imerge Beta Tester, HitFilm Beta Tester Posts: 5,250 Staff

    No, masking off the markers will leave you nothing to track, and cause it to fail for sure.  Those markers are the only texture on the greenscreen, that's pretty much the point of that whole experiment.  Read the description, and it explains that even though you don't usually need markers for planar tracking, you HAVE TO use them for cases like this, as there is no texture in the greenscreen without them.  That's the lesson they are trying to teach with that specific shot.

    What types of tracking are you running?  What are your track settings in mocha?  Also, I've not used mocha for AE much, my experience is with mocha Hitfilm, and I'm not sure how much they differ.  I'm pretty sure the main interface is the same though, and the differences are mainly in the export options.

  • JWA2014
    JWA2014 Website User Posts: 6

    I tried doing it with both the markers and without the markers just as a test to rule stuff out. 

    What do you mean by what type of tracking am I using? I am using planar tracking comprised of x-splines. Settings: Min pixels used 20%, Smoothing level 0%, Motion Translation - Shear(tried with perspective turned on as well), Large Motion, Luminance as the input channel.

    I'm really at a loss here. It's a nice challenge but I can't seem to crack this one! I would gladly pay to stream the volume that this tracking exercise is on, but they don't tell you the volume it's on. 

  • AxelWilkinson
    AxelWilkinson Staff Administrator, Imerge Beta Tester, HitFilm Beta Tester Posts: 5,250 Staff

    I meant what type of motion were you tracking, sorry.  I would turn on translation, scale, rotation, shear and perspective.  

    I tried tracking that shot, and started by going to frame 1, creating a spline just large enough to contain all the blue markers and avoid the arm, and tracked through straight ahead, and it did pretty good.  It wasn't perfect but with that drastic of a change in perspective and distance, its not surprising that a bit of track adjustment might be needed.  It definitely held to the plane though, and got me very close to a useable result.  So you might try that.

  • JWA2014
    JWA2014 Website User Posts: 6

    Nice. Thanks Axel. I will give that a try a little later and let you know how it went.

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,810 Ambassador

    @Axel, Mocha Hitfilm, AE and Pro all have the same interface--just varied options are greyed out (Mocha Hitfilm doesn't export roto, AE doesn't do camera solves.) 

    @jwa2014: take a look at this tutorial. Mocha has the "Adjust Track" module, which is basically a corner pin to help fine-tune your track. 

  • JWA2014
    JWA2014 Website User Posts: 6

    still having trouble with it. I could keyframe the middle and end but i don't see how i'm going to get those cornerpins on the corners in the beginning

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,810 Ambassador

    Hmmmm mental note:Download clip and look at it. 

  • JWA2014
    JWA2014 Website User Posts: 6

    thanks all. i got the track finally! Just used the markers didn't even worry about the board. Turned on perspective as Axel suggested. I'm sure i'll have to tweak it a bit with some keyframes here and there but i was able to get a good solid track to work with

  • BriRedd
    BriRedd Website User Posts: 97 Just Starting Out*

    My turn!

    I'm using the same clip here. Masked out the arm - just tracked the blue markers (with a single layer) while ignoring the paintings outer edges. Have Translation, Scale, Rotation, Shear and Zoom checked - 40% pixels used.

    Started in the middle and tracked forward and backward. I have a solid track, no drifting of the Surface and Grid but I can't get Mocha to solve! I've used "Auto" and get, "Camera motion can't be computed in Auto mode. Please manually select a solver type."  PTZ doesn't fit and the manual modes need an additional layer(s).

    Do you track the blue markers individually thus giving more layers even though those layers are on the same plane? Seems like a pretty straight clip to track and yet ...

     

  • Simes
    Simes Website User Posts: 21
    edited May 2015

    If I understand this stuff right, you can't use PTZ for that shot because the camera is actually moving, so to get a solve you'll need multiple planes. If all you want to do is replace the board surface, then you don't need a solve, and exporting the shape data should (I think) give you everything you need.

  • BriRedd
    BriRedd Website User Posts: 97 Just Starting Out*

    Thanks for the reply, Simes!

    Perhaps I'm misunderstanding something, I believe I need tracking points to attach a photo of a painting to. The shape data just gives me a shape. 

    I think the imported photo gets attached under the tracked green screen which is then keyed out. There is a persons arm over the green screen so you can't just attach the photo on top.

    I did try to import the shape data which verified that the actual track is solid but I need tracking points. 

  • Simes
    Simes Website User Posts: 21
    edited May 2015

    I probably got that wrong, then. I've been bashing my head against camera solves all week so I'm pretty confident about that part, but not so much on the basic replacement bit. I'm not so sure about the arm, I'd have thought you'd need to roto it out in any case but I could be wrong. I am trying to get to grips with a lot of this stuff myself. :)

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,810 Ambassador
    edited May 2015

    @BriRedd @Simes what's throwing you guys in this thread is the differences between Mocha AE and Mocha Hitfilm, both of which are subsets of Mocha Pro. 

    Mocha AE can export corner-pin data to AE. Mocha Hitfilm exports camera solve data and shape data only. Not corner pins. Although exported camera solves do give point data for the corners and centers of your surfaces, exported camera solves are 3D data while Mocga AE corner pin exports are 2D data. 

    If the camera is moving, then you would have to solve with two planes to get accurate 3D positioning. Yes, exporting the camera solve lets you get corner and center points for the exported surfaces, but it's not the same workflow as Mocha AE corner pin data. 

    Solving multiple splines on the painting won't help--in fact, it hurts! The painting is a single plane, and tracking it in two layers is trying to tell mocha two objects exist in the same location, which means there's no parallax for depth. 

    I haven't looked at the source clip (I am on my phone), but here's a way to "trick" Mocha Hitfilm. 

    First, define a spline for something that isn't the painting: track one frame. Go into the Dope Sheet and copy that keyframe and paste it to every frame. Solve as PTZ.  This lies to Mocha, telling it you have a static camera. 

    Now track your painting. Make sure your surface is aligned with the painting corners. This lies to mocha and tells it the painting is moving. Export and you have your points. 

    To stress a point, this hack will not give you an accurate camera solve for full 3D positioning! Remember, we lied to mocha, told mocha it was a static camera, then told mocha the painting is moving. So, this should let you get corner pin data, but don't try to use this solve to add anything else! For an accurate 3D environment, you'd have to solve the camera with two planes. 

    Take a look at this tutorial. About an hour in Martin Brennan shows the Dope Sheet trick I mention above (it's the segment where he tracks a face to attach a 3D object). 

    And this tutorial where Axel covers solving a camera first, then tracking/exporting an object. 

    That said, if you need a corner pin, can't you track each corner of the painting with Hitfilm's point tracker parent points to each track and use those points for the corner pin? That's usually a better workflow in Hitfilm. 

     

  • BriRedd
    BriRedd Website User Posts: 97 Just Starting Out*

    Triem23 - I'm a little late with my thank you but your reply is greatly appreciated!

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,810 Ambassador

    You're welcome. Hope you solve your track.