Motion Path

When adding keyframes to a 2D Parameter, Autograph draws a trajectory in the Viewer based on the Parameter's changes over time. This trajectory is called Motion-Path and is most often used to visualize the movement of a Layer. Although Position Parameter isn't the only one concerned, we'll start by adding keys to it to keep things simple.

With two keyframes added to the Position parameter, at different times and for different values, a Motion-Path appears in the Viewer:

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Managing space and time separately

When animating a Layer, you need to ask two questions:

• Which path takes my layer?
• How fast is the layer moving along this trajectory?

The Motion-Path's main purpose is to answer the first question, representing the spatial evolution of a 2D parameter.

For the second question regarding the velocity on this trajectory, other tools are more suitable for that:

• Timeline/Dopesheet: for handling Keyframes
• Retime Graph: for managing the Layer's position on this Motion Path over time
• Motion Path Tool: for editing several Motion Paths at once.

Each keyframe in the Position parameter of the Timeline is spatially represented by one of the Motion Path control points.

If you select a keyframe in the timeline, the corresponding control point will also be selected in the Viewer.

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These control points are displayed as squares, in yellow when selected.

Position Motion-Path

A Motion-Path is made up of several dots, each representing the Anchor Point position for each interpolated image between the two Keyframes.

If we bring the Keyframes closer together, we see that the dots density decreases as the number of frames separating them also decreases.

|||VIDEO DU L'ETAT AVEC DEUX KEYFRAMES SUR UNE SECONDE. AVEC LES CLES QUI BOUGE

The only visual indication of the Layer's speed is the distance between the dots. The further apart they are, the faster the Layer moves.

Motion-Path Tangents Handling

Creating two keyframes on Position Parameter produces a straight Motion-Path by default. However, clicking on the first point brings up a yellow tangent.

Moving this tangent will bend the trajectory:

|||VIDEO DE LA TANGENTE DUI BOUGE

Setting Tangents Size

If you click on the last point, you won't see this tangent, as its handle is at the same place as the control point.

But by pressing the Alt/Option key and clicking and dragging this point, you can draw a new tangent and bend the Path on the other side.

|||VIDEO DE LA TANGENTE DUI BOUGE

• A single click on a control point with the Alt/Option key gives tangents a null size.
• Another click in this situation assigns a new default size.
• This function is also available by right-clicking on a point and choosing Toggle Tangents.

Breaking tangents

By pressing the Ctrl/Cmd key and clicking on tangent handles, you can dissociate them to create an angle.

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Intermediate Keyframe Tangents

Move your playhead between the two keyframes to position your layer halfway along the Path and move the Layer in the Viewer to create a new Keyframe and therefore a new control point.

Again, we can adjust this new point's tangents:

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Moving the entire Motion-Path

To move the entire Motion-Path, you need to select and then move all control points. When using the 2D Transform Tool, a selection rectangle will select Layers, not control points.

These points can be quickly selected:

• By selecting all Parameter keyframes in the Dopesheet, which will select all control points.
• By clicking on the Parameter name, which will select all keyframes.

But there's a feature that lets you go even faster. Right-click on any point and choose Select All Keyframes on Path.

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Adaptive Keyframes and Motion-Path

When a keyframe is set to Adaptive Time, it's drawn on a Path in a different way.

Right-click on the intermediate control point in the Viewer or on the corresponding Keyframe in the Timeline and select Adaptive Time (or press the X key after selecting it).

The control point is now drawn as a small circle:

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Tangent and Spatial Interpolation Presets

Autograph lets you manually manage the control points' tangents with the tools mentioned above. But it also offers presets to define them automatically, based on the adjacent points' positions.

To access these options, you need to:

• Go to the DopeSheet module
• Show the Keyframe Properties Dock

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After selecting one or more control points, the Spatial Interpolation section contains an Interpolation Parameter defining the mode applied to the current selection.

Interpolation presets using three points:

• The current control point
• The previous one on the path
• The next one on the path

Linear:

• The preceding tangent always points to the previous point.
• The next tangent always points to the next point.

|||VIDEO DU DEPLACEMENT SUR 3 POINTS, AVEC LE POINT CENTRAL QUI BOUGE

Linear interpolation will therefore always create an angle at the control point.

Smooth:

• Orient tangents horizontally if the current control point is the highest or lowest of the three.
• Orient tangents vertically if the current control point is furthest to the left or right.
• Entre les deux limites, les tangentes subirront une rotation

|||VIDEO DU DEPLACEMENT DU POINT DE DROITE

Catmul-Rom

• The tangents are parallel to the line formed by the previous and next points.
• Their lengths are proportional to the distance between the two points.

The adjacent points' tangents are not taken into account when calculating the tangents of the current point.

|||VIDEO DU DEPLACEMENT DU POINT DE DROITE

Cubic:

Ensuring tangent continuity with Smooth Bezier Interpolation and C2 Continous Tangents.

• Tangents are the same size on both sides
• The adjacent points' tangents are taken into account.
• The curve's continuity will be computed automatically without the need to manage tangents.

|||VIDEO DU DEPLACEMENT DU POINT DE DROITE

Broken:

Quelque soit le mode utilisé,Whatever mode you're using, moving a point or modifying a tangent will immediately switch the point's spatial interpolation to Broken mode. This term refers to the ability to break tangents (by pressing Ctrl / Cmd) and manipulate them without constraint.

Visualize rollbacks on the Motion-Path or its extension

Elastic or Bounce** temporal interpolations move the layer along the motion path in a non-linear way.

• Bounce causes the layer to bounce off the last key and back along the motion path several times.
• Elastic, in addition to going backwards like Bounce, extends the Motion-Path beyond the last key.

Using the Retime Graph can also produce non-linear movement along the Motion-Path.

In the case of a rollback or extension, the Motion-Path is drawn much thicker.

|||IMAGE D'UN MOTION PATH AVEC LES MODE BOUNCE ET ELASTIC

Not only for layer's position parameter

Although the Layer Position parameter is the most common case of Motion-Path use, we began by pointing out that it can be generated by any 2D spatial parameter.

Let's take the example of a God Rays modifier applied to an image. After setting its Scale parameter to 6.0, its Position parameter is used to define the center of the rays.

By creating two keyframes on the Position parameter, then selecting it in the Properties section or in the Timeline, a Motion Path appears representing the trajectory of this point, whose tangents can be modified to curve it.

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