Help with setting the right Tracking Splines in Mocha

Hey guys,

I'm trying to set up a 3D Text in a shot similat to how Axel did in this video ( a while ago. However my shot seems to be a bit tricky as there are few destinguisahable shapes to track, at least thats what I think, I'm not very experienced in using the plug in.
This is a picture of the shot:
It's a simple drone flight towards the house in the back. Na change in direction or altitude during the flight.
I Marked the area where i wanted to place the text and want it to appear to "stick" in the snow.
So messed around a bit trying to get a camera solve. I learned from the tutorial (and others on YT) that it's best to track a plane that is near the area where the text should be placed later on. I gave it a few tries but I didn't seem to have hit the right spots just yet, as the grid warps when playing through the track.
Is this shot simply too bad to track because it lacks Detail on the ground areas? or is there a possible workouraound i havn't thought of yet.
Would appreciate any suggestions to where i should place my areas for tracking.

Thanks for any help in advance!


  • Triem23Triem23 Moderator
    edited January 2019

    You have two issues with that shot. First, there is almost no detail in that snow: Mocha works by tracking areas of TEXTURE, which requires some contrast. There just isn't much in that snow at all. Second, Mocha is a PLANAR tracker which requires something that can be more-or-less described as a flat rectangle. From the shadows it looks like the area you've highlighted is a dip right next to a rise - a double curve and not flat at all. Now the "flat" you can often fake/cheat quite heavily, but that particular are is more or less no good.

    Suggestion: Track one of the background mountain "layers" (there are two different ridges in the shot) and track that tree just above and to the right of that highlighted area. That's the two points of reference you need to generate the 3D data, and that tree is the closest thing you have to a texture area near where you want to place your text.

    The mountains can be treated as a flat plane, if the drone was moving straight backwards and forwards, the tree should be something you can "fake" as flat. If the drone is only moving forward/backward and you have no turns or tilts of the camera then you'll only need to track position scale and rotation. You should'nt have skew or perspective to worry about.

  • edited January 2019

    Never mind, he's fixed it; and almost got the apostrophe in the right place. ;)

  • @Triem23 Thanks a lot! Your suggestion worked. As you said correctly the highlighted area was nowhere near a flat plane so i guess that's why i got bad solves all the time, as i tried to use the area to track. 
    The Solve now works as it should and the text stays lacked in place as the drone moves towards it, however i ran into a couple of different issues:
    I duplicated the clip, roughly masked out the ridge of the first snowdrift and placed the text layer in between. I animated the mask acordingly to the movement of the drone to create more depth. It looks decent however at the mask leaves some kind of grey rim that i cant explain at all:
    The two layers have the same position and anchorpoint attributes and i really have no clue where this grey line comes from. when trying to feather it, it gets worse:
    Both are 2D Layers. The line stays there even when I disable/delete all the other layers and it stays there when i render and export the clip, as well. Never run into this issue maybe you know what could cause it.

    The second thing: Is there a possibility to create a shadow that matches the natural lighting conditions of the scene? I currently have a Spotlight behind the text to illuminate it from the back. I enabled Cast shadow for the light, cast shadows for the text transformed the Clip into a 3D layer and enabled recive shadows. I assume I wont be able to get a shadow for the text that matches the shadow of the tree this way as the light comes from behind the text and there is no "canvas" for the shadow to be projected onto as the clip is located behind it as well. Is there another way to get a matching shadow with lights or do i have to "fake" one by using for example an additional text layer?  

  • edited January 2019

    Do you have the mask on both layers? If so, remove it from the rear one. Masks don't quite join up if you duplicate and invert one on a second layer on a non-straight line.

    If you made a hole shape in anything with a mask, then placed a second layer on top with the inverse of the mask to fill in the hole, it wouldn't quite match up. What you're possibly seeing is the black from the nothing behind the layers.

    You need a full layer, the text in front, then the foreground - masked - in front of that.

    If not that, then...

  • Triem23Triem23 Moderator

    For the mask, in Mask>Shape set feather to "Out." You're currently feathering the inside of the mask bringing in more transparency. 

  • Wouldn't that only be a problem if there is nothing behind it?

  • @ Palacono @Triem23 The mask was only on one layer. So i had  Full layer -> Text -> Masedked layer. Feather was at 0. I, too thought that the line originates from the black background, but i found what caused the issue:

    With this checked off it works just fine.

    So the remaining thing is how to get a matching shadow.

  •  Ooh, so another mocha bug. :( Worth telling that to , as they've had a few others to poke about at in there recently; could be connected.

  • Triem23Triem23 Moderator

    @Palacono probably not technically a bug. Since mocha generates its own masks to apply to a layer it probably, by design, generates black to premultiply. It's seems more of an interaction between two opposing masking systems on the same layer.

    But, good info to file away. 

  • @Triem23 Ah yes, mocha masks aren't same as Hitfilm's. They don't translate from one to the other at all well (reported ages ago, told nothing can be done: it's mocha messing them up in the translation). So OP must have had both the plugin mask still active, as well as one he'd exported as a comp and used on the other layer because you can't cut'n'paste them from the plugin (wish you could).

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