Curve Editor: Value Graph

Graph Editor Overview

The Graph Editor is one of the Timeline modules. It is accessible on the right side via a button representing a curve.

Once activated, the right part of the Timeline is replaced by a graph where you can modify the interpolation of curves created from keyframes, as well as inspect the evolution of a parameter after Generators and Modifiers have been applied.
This module has 2 different modes:

Value Graph: displays and controls the evolution of numerical parameters over time
Retime Graph: displays and controls the evolution of a layer or spatial parameter along a Motion Path

This chapter will go over Value Graph mode, and the next chapter will focus on the Retime Graph.

Displaying a Parameter in the Graph Editor

To display the evolution of a parameter in the Graph Editor, select it in the Timeline or Inspector.

Depending on whether the selected parameter type is spatial, the Graph Editor will automatically switch to the Value Graph or Retime Graph.
In the example above, the layer Rotation is animated by two keyframes that go from 180 to 0 degrees over a period of 1 second.

The vertical scale represents the value in degrees: on the left, values go up to 180
The horizontal scale represents time: on the right, the last keyframe is positioned at 1 second

Navigating the Graph Editor

The vertical scale displays values from 0 to 180 because selecting the parameter automatically fits the graph editor between the keyframe with the highest value and the one with the lowest.
The shortcuts for moving and zooming in the graph are the same as those for moving in the Dope sheet, with a slight difference for zooming.

Pan (in all directions):
- space + left-button
- middle-button
- alt/opt + left-button
Zoom:
- alt/opt + "Mouse wheel": zoom in and out horizontally until the entire composition is visible, then zoom in and out vertically
- "Mouse wheel": zoom in and out both horizontally and vertically
- ctrl/cmd + alt/opt + left-button: the direction of the mouse will determine whether the zoom is horizontal or vertical
- f key to fit the current selection

You can also use the scroll bars at the bottom.

Warning: Shortcuts in Autograph are contextual and dependent on mouse position. These shortcuts are valid when your mouse cursor is over the Graph Editor.

A button at the top-right of the panel allows you to fit the current selection, rather than pressing the f key.

Keyframe Properties Dock

On the right, the Curve Editor permanently displays the Keyframe Properties Dock already mentioned in the Keyframe section.
This dock displays information on the selected key. If several keys are selected, the one furthest to the left is displayed, even if the dock shows that two keyframes are selected.

Warning: If several keyframes are selected, any changes made in the Dock will be applied to all these keys.

Analyzing the Rotation animation in the Value Graph is easy to understand, as we've selected a single parameter made up of a single dimension for a 2D layer.

Selecting a key displays the following parameters:

Time: the time at which the key is located, defined in seconds
Value: the parameter value stored in the key
Interpolation: the interpolation type assigned to the key
Adaptive Time: switches a key to Adaptive mode whenever possible

The Slope section defines the tangent parameters displayed on either side of the point.

Left Slope: tangent slope to the left of the point
Left Amount: tangent tension defined by its length
Right Slope: tangent slope to the right of the point
Right Amount: tangent tension defined by its length

Warning: Depending on the interpolation assigned to a keyframe, the Left or Right parameters may not appear in the dock.

Changing Keyframe Interpolation

Interpolation of selected points can be changed during playback to quickly test the available modes.
Press the middle button to scroll through the list without having to click on the scroll bar:

In the video above, the Play Visible Range option has been activated to loop only what is displayed in the Graph Editor.

Manual Tangent and Point Adjustment

Keyframe values can be modified in the Keyframe Properties Dock or by manipulating graph points directly.

Moving a point horizontally changes its Time parameter
Moving a point vertically changes its Value

Moving a Keyframe Between Images

The high precision with which these values can be modified allows you to place a keyframe between two images in the composition. But just like with Layer Time Offsets, pressing the ctrl/cmd key while moving a point allows you to move a key between two frames.
In the video below, the point is first moved without the ctrl/cmd key, snapping it to the nearest frame, then this key is pressed while moving.

Adding a Point on Curve:

To add a point to a curve, press the alt/opt key and click on it.

In the video above, we also switch all keyframes to Horizontal mode to create acceleration and deceleration between each point.

Handling Several Points using the Control Box

Selecting several keyframes with a selection rectangle brings up a control box.

Handles on edges stretch points and their tangents, horizontally or vertically
The box corners evenly resize the whole box
Central point moves all points

Restrict Movement to One Dimension

By default, the center point can be manipulated in any direction. But a button at the top of the Curve Editor allows you to constrain point movement to one axis only.

This axis is automatically defined according to mouse direction.

Manually Tweaking Tangents:

Shortcuts used to manipulate tangents are the same as those used to edit points on a Motion Path.

Press the alt/opt key, then click and drag the point to draw a new tangent
Press the ctrl/cmd key, then a tangent, then click and drag a tangent point to break them

Working on Several Separated Dimensions

The Curve Editor in Value Graph mode is not really recommended when working with spatial parameters in Unified mode (which is the default for Position). This is why it automatically switches to Retime Graph mode when this type of parameter is selected.
However, if Position is switched to Separated mode, each parameter is 1D and can be manipulated independently.

Colors are used to differentiate dimensions:

X: Red
Y: Green
Z: Blue (for 3D layers and items, such as mesh layers, cameras, and lights)

Parameter names are displayed next to the corresponding curves.

Color parameters in Separated mode will be represented by Red, Green, Blue, and White curves for the Alpha channel. Below is a Circle Generator color parameter.

Inspecting Parameters using Generators and Modifiers

Selecting a parameter allows you to display its animation curve, regardless of the way you animate it:

Keyframes
Generators
Modifiers

Generators

By adding a Noise Generator on a Rotation, the Graph Editor will display its evolution over time.

Once this Generator has been added, we can click on the Rotation parameter again to see its evolution, then access the Noise parameters.

Modifiers

The same is true if this parameter is animated with keyframes, while undergoing modifications by adding a Modifier.

Once again, a Noise Modifier is added to the keyframe animation:

Note: Two curves are displayed in the Graph Editor. The solid curve represents the original movement created by the keyframes, while the dotted one represents the movement after the Modifier has been applied.