ShotANVIL: Tracking Options (Tutorial)

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Hi. In this tutorial I'm going to explain the settings for motion tracking,

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which are grouped into a pre tracking menu on the left and a post tracking menu

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on the right.

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These tracking settings are common across all of our moca based tracking

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products. We are reviewing them here in the Slice X editor,

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but they're the same for Paint X and others.

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Let's explain a few terms and concepts before we go over the individual

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parameters. When we're tracking,

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the movement is modeled in two different ways when we choose to track and

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translate scale rotate mode. The tracker is solving for the X and Y position,

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simple two d rotation in the Z axis and the overall scale,

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but ignores perspective distortion.

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The perspective mode adds perspective distortion to the mix and is the setting

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you will most commonly want to use.

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The benefit of tracking and perspective is that when you want to track an

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extreme rotation or movement,

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we'll better follow the motion of individual shapes and textures within the

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tracking area.

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If you were just to try and match that motion with a translate scale rotation

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mode,

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the shapes will most certainly lose their connection to the image due to the

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lack of distortion.

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Let's look at the apply track mode setting.

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Choosing position only means that the track layer will only move in X and Y and

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ignore rotation and distortion.

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This is good for call outs such as when we might want a text label to track an

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object's position,

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but stay flat in the same size on screen with no rotation or scaling setting

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apply track to perspective mode will treat the motion as if applied to a two D

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plane viewed in three D space.

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It will effectively warp the shape mask with four corner points to better map to

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three D surfaces. To reiterate,

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tracking model and apply track mode should be set to perspective in most cases

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with the exceptions being text callouts and some specific effects.

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So now let's track this sword using a detailed shape mask. As mentioned,

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we will use the perspective tracking model and set apply track as to

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prospective mode as well, and then we can track it.

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We can see after tracking that it's working quite well.

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There is a tiny bit of slipping,

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which we could fix by adding a couple of shape key frames to,

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to tweak the points in the mask over time,

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but we will save that for another tutorial.

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Let's have a look at some additional options to see other ways that we could

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have approached it. If you are tracking a very small shape,

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sometimes there simply isn't enough information to get a good track from the

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shape itself. In this case, we can change the track shape oversized property,

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which will expand the tracking area outside the shape mask.

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This ensures that the tracker will have more details to use for calculating the

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motion without affecting the way the clip is masked.

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We can also change the track shape overlay opacity to give us a clearer view of

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the underlying pixels.

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So while we tracked in perspective mode after tracking,

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we can switch the track apply setting to translation.

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We can see that it pins the shape to the center of the tracked area,

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but ignores changes in scaling rotation and perspective distortion,

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exactly what we need for tracked callouts.

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Let's make sure again that the track apply setting is in perspective mode, and

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then have a look at the track smoothing parameter.

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If the track motion has some jittery high frequency vibrations,

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we can turn on smoothing and choose how many seconds we want to smooth over.

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In this case, the results were already smooth.

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Copy track data and paste track data allow us to copy motion tracking to

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different layer groups such as two different groups of strokes and pan X or

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between instances of slice X. After choosing copy track data,

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we can immediately see that paste track data is available in the right side menu

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indicating that the track motion was copied successfully and is now available

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for pasting. The

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next settings here are for solving specific problems with bad tracking

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solutions. For example, if a track fails halfway through,

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generally you want to stop the track, move the playhead to the last good frame,

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and then use the delete track data forward function to clear the unusable

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tracked motion.

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We can then try other approaches to create the second part of the track by

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changing the shape somewhat or choosing a completely different area of the

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image. The details of this will be covered in a separate tutorial.

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We can also just delete track data at the current frame via the menu or using

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the hotkey queue.

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This is useful if we only have a couple of bad frames that we need to delete.

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Delete track data backwards, as we would expect,

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deletes the track motion before the current frame and delete all track data

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clears the entire track.

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The yellow tick mark here indicates that there is valid track data at that

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frame. If I delete the track data forward,

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you'll see that the yellow line here indicates that track data is on this part

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of the clip only,

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and that the track motion is clear where there is no line or tick mark.

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I can undo that using the menu or command Z and get the track data back again.

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So that's the basic overview of the tracking menu parameters.

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We will publish additional tutorials demonstrating in detail how to use these

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functions to solve difficult problems such as dealing with shots with a subject

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you're tracking, goes behind other objects or needs to be tracked out of frame.

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Please go to coremelt.com/downloads to get your free trials.