利用者:Jaredr122/Doc:2.6/Manual/Animation/Editors/Graph/FCurves

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Working with F-Curves

Once you have created keyframes for something, you can edit their corresponding curves. In Blender 2.5, IPO Curves have been replaced by F-Curves, however, editing these curves is essentially still the same.

The concept of Interpolation

When something is "animated," it changes over time. In Blender, animating an object means changing one of its properties, such as its X location, or the Red channel value of its material diffuse color, and so on, during a certain amount of time.

As mentioned, Blender's fundamental unit of time is the "frame", which usually lasts just a fraction of a second, depending on the frame rate of the scene.

As animation is composed of incremental changes spanning multiple frames, usually these properties ARE NOT manually modified frame by frame, because:

• it would take ages!
• it would be very difficult to get smooth variations of the property (unless you compute mathematical functions and type a precise value for each frame, which would be crazy).

This is why nearly all direct animation is done using interpolation.

The idea is simple: you define a few Key Frames, which are multiple frames apart. Between these keyframes, the properties' values are computed (interpolated) by Blender and filled in. Thus, the animators' workload is significantly reduced.

Example of interpolation

For example, if you have:

• a control point of value 0 at frame 0,
• another one of value 10 at frame 25,
• linear interpolation,

then, at frame 5 we get a value of 2.

The same goes for all intermediate frames: with just two points, you get a smooth growth from 0 to 10 along the 25 frames. Obviously, if you’d like the frame 15 to have a value of 9, you’d have to add another control point (or keyframe)…

Interpolation and Extrapolation settings

F-curves have three additional properties, which control the interpolation between points, extension behavior, and the type of handles.

Interpolation Mode

You have three choices (T, or Curve » Interpolation Mode):

Constant

There is no interpolation at all. The curveconstantly have the value of its last keyframe, giving a discrete (stairway) “curve”. Very seldom useful.

Constant.

Linear

This simple interpolation creates a straight segment between each neighbor keyframes, giving a broken line. It can be useful when using only two keyframes and the Extrapolation extend mode, to easily get an infinite straight line (i.e. a linear curve).

Linear.

Bezier

The more powerful and useful interpolation, and the default one. It gives nicely smoothed curves, i.e. smooth animations!

Bézier.

Remember that some Fcurves can only take discrete values, in which case they are always shown as if constant interpolated, whatever option you chose.

Extrapolation

Extrapolation defines the behavior of a curve before the first and after the last keyframes.

There are two basic extrapolation modes, (⇧ ShiftE, or Channel » Extrapolation Mode):

Constant

The default one, curves before their first keyframe and after their last one have a constant value (the one of these first and last keyframes).

Linear

Curves ends are straight lines (linear), as defined by their first two keyframes (respectively their last two keyframes).

The two extensions available for Ipo curves.

Constant.

Extrapolation.

Additional extrapolation tools are located in the F-Curve Modifiers

Handle Types

There is another curve option quite useful for Bézier-interpolated curves. You can set the type of handle to use for the curve points V

Automatic

Keyframes are automatically interpolated

Auto handles

Vector

Creates linear interpolation between keyframes. The linear segments remain if keyframe centers are moved. If handles are moved, the handle becomes Free.

Vector handles

Aligned

Handle maintain rotation when moved, and curve tangent is maintained

Aligned handles

Free

Breaks handles tangents

Free handles

Auto Clamped

Auto handles clamped to not overshoot

Auto clamped handles

Direction of time

Although F-curves are very similar to Bézier curves, there are some important differences.

For obvious reasons, a property represented by a Curve cannot have more than one value at a given time, hence:

• when you move a control point ahead of a control point that was previously ahead of the point that you are moving, the two control points switch their order in the edited curve, to avoid that the curve goes back in time
• for the above reason, it's impossible to have a closed Ipo curve

Two control points switching: the curve can't go back in time!

Before moving the second keyframe

After moving the second keyframe

Curve Selection

By default, when you add keyframes to a channel, the Graph Editor displays them in Edit Mode. Just like in the 3D View, you can toggle the editability of a channel by pressing ⇆ Tab. In the Channel Box, the lock icon also toggles between edit and "non-edit" mode.

Selection Tools

You can select curve handles clicking LMB (or ⇧ ShiftLMB for multiple. You can select an entire key by selecting the center point, or just select one the handles

You can also (de)select all visible curves with A (or Select » Select/Deselect All), and do a border-selection with B (or Select » Border Select) – simple LMB click-and-drag to add to the selection, and RMB (or CtrlAltLMB ) to remove from the selection.

Select All A

In edit mode, select/deselect all keyframes

In locked mode, select/deselect all visible channels

Invert Selection CtrlI

Inverts selected keys

Border Select B

Allows selection of keyframes within a region

Border Axis Range AltB

Axis Range...

Border (include Handles CtrlB

Include Handles, handles tested individually against the selection criteria

Columns on Selected Keys K

Select all keys on same frame as selected one(s)

Column on current Frame CtrlK

Select all keyframes on the current frame

Columns on selected Markers ⇧ ShiftK

Select all keyframes on the frame of selected marker(s)

Between Selected Markers AltK

Select all keyframes between selected markers

Before Current Frame [

Select all keys before the current frame

After Current Frame ]

Select all keys after the current frame

Select More Ctrl+ NumPad

Grow keyframe selection along Fcurve

Select Less Ctrl- NumPad

Shrink keyframe selection along Fcurve

Select Linked L

Selects all keyframes on Fcurve of selected keyframe

Editing Curves

Transformations

Transform properties

You can grab (G), rotate (R) and scale (S) the selected curves (those visible, with white control points/keyframes) – operations also available from the Curve » Transform sub-menu.

Additionally, for translation and scaling, you can lock the transformation along the X (time) or Y (value) axis, as usual by hitting X or Y during transformation.

Transform Properties

For precise control of keyframe position and value, you can enter values in the Active Keyframe section of the Properties Panel.

Snapping

You also have the classic “transform snapping” features: holding Ctrl while transforming will snap it to one-frame/one-value steps, while holding ⇧ Shift will slow down the movement, increasing its precision. Note however that using ⇧ ShiftCtrl just slows down the movement, without reducing the snapping steps.

(⇧ ShiftS or Key » Snap) You can snap keyframes in several ways:

Current Frame

This option will move all selected keyframes to the currently active frame.

Cursor Value

This option will move the selected keyframes to the current position of your 2d cursor in the graph editor.

Nearest Frame

This will horizontally (timely) move all keyframes of the selected curves to their nearest frame (e.g. a keyframe defined at frame 23.2 will be moved at frame 23).

Nearest Second

This will horizontally (timely) move all slected keyframes of the selected curves to their nearest full second (e.g. a keyframe between 00:02 and 00:03 seconds will move to either 00:02 or 00:03 depending on which is nearer).

Nearest Marker

This will horizontally (timely) move all keyframes of the selected curves to the marker nearest to them (see also Markers).

Flatten Handles

This is only useful with the default F-curves: it will rotate all control points of the selected curves to set them horizontal.

“Flatten Handles” snapping example.

Before Flatten Handles.

After Flatten Handles.

Auto-snap

Auto snap is another way of constraining keyframe position. The selection box in the header allows you to set how keyframes behave when you move them

Nearest Marker

Snap x-axis to marker positions

Nearest Frame

Snap to frames (default)

Time Step

Snap to 1.0 frame/second intervals

No auto-snap

Disable auto snapping

Copying

You can copy one or more keyframes into a buffer, and then paste them into the same curves. This is done through two header buttons:

• The “copy” CtrlC button (down arrow) copies the selected and visible curves into the buffer.
• The “paste” CtrlV button (up arrow) pastes the buffer content into the corresponding visible curves of the current channel.

Note that this tool is not working (even though available) in “keyframe” mode. And in edit mode, only the selected points are copied/pasted (not the whole curve…).

You can also Duplicate keys through the Key menu.

Deleting

To delete a keyframe, select it (in “default” mode), and hit X (or use Curve » Delete).

Mirror

You can mirror the selected curves (⇧ ShiftM or Curve » Mirror), either Over Current Frame (i.e. the green cursor), Over Vertical Axis (i.e. frame 0), or Over Horizontal Axis (i.e. value 0.0).

Cleaning

O (or Curve » Clean Keyframes menu entry) Cleaning keyframes resets keyframe tangents to theier auto-clamped shape, if they have been modified.

Fcurve before cleaning

Fcurve after cleaning

Smoothing

(AltO or Curve » Smooth Keys) There is also an option to smooth the selected curves , but beware: its algorithm seems to be to divide by two the distance between each keyframe and the average linear value of the curve, without any setting, which gives quite a strong smoothing! Note that the first and last keys seem to be never modified by this tool.

Fcurve before smoothing

Fcurve before smoothing

Sampling and Baking Keyframes

Sample Keyframes ⇧ ShiftO

Sampling a set a keyframes replaces interpolated values with a new keyframe for each frame.

Fcurve before sampling

Fcurve after sampling

Bake Curves AltC

Baking a curve replaces it with a set of sampled points, and removes the ability to edit the curve.