An Action consists of an unlimited amount of "channels", with each channel having a related Ipo (an entire collection of animation curves - eg. LocX,LocY,LocY,R,G,B,etc.). Actions use the channel names to define which objects (or bones) the animation curves should work on.
Previously, Actions were available for Armature Poses only, with channels for both Bones and Constraints. Now, however, Actions have been expanded to work in other areas of the animation system.
You enable this new funcationality in the Ipo Animation Curve editor (Ipo Window): check the "Action" icon to the left of the "Ipo Mode" selection menu. When you set this option, an Action is automatically created for you. It also automatically copies the Ipo to the Action (copying it back if you disable the option).
At the moment, this new feature works for Object and Shape Ipos only. When checking the Action Window, you can see that it creates custom channels, with the names "Object" or "Shape". Please note that Object Constraints also become part of the Action!
For Poses the use of Actions with Ipos is set by default and cannot be disabled.
In the NLA editor you see a representation of all Objects with either Actions or Ipos. On a per Object basis, you can add "Action Strips" (SHIFT+A), adding as many Actions you like, allowing you to mix different Actions and edit their timing and relationships non-destructively. Each Object can only have one active Action, which is displayed in the Action Editor. This active Action is the one which will receive any new keys you insert, and whose keys you can directly edit.
The NLA editor displays it all as follows:
1) Only when an Object has an Ipo, an Action or NLA strips is it shown in the NLA editor. The top-most horizontal bar for an individual object shows the Object's name to the left, and any "keyblocks" (the diamonds that represent keyframes) for the Object Ipo on the right.
2) Below the Object bar the active Action is shown, and the "keyblocks" for the Action Ipos.
3) Finally, the "Action Strips" are drawn. The active Action Strip is indicated with a dot icon. Clicking on a Strip itself or on the left-hand bars will set a strip to being the active Action.
4) The button to the immediate left of the Object name toggles Blender between evaluating the entire NLA and displaying the results in the 3D window, or only evaluating the active Action.
Since Action Strips in the NLA editor can be moved or scaled, the timing of Actions can be altered. Blender now displays this timing change in both the NLA and Action editors, and corrects timing for inserting key positions in the 3D window.
If you want to work on the timing of the keys within the Action itself (as opposed to just stretching and moving timing of the Action as a whole in the NLA window), click on the (lefthand in NLA window) Action name itself. It will mark that Action with a dot icon, making it the active Action.
Locked Strip length
In older versions, changes to the overall timing of the animation curves in an Action caused confusing situations, as the Action's strips in NLA just remain the same length. By setting the strips to Locked (from the N-Key properties panel in the NLA window), NLA will alway keep strip length up-to-date with your Action edits so that all keys are included. Locked mode is the new default, as it is far superior to the old behavior, but older files will have to be updated manually for this feature to work.
ALT+S Size Options
This menu has 2 options. The first (Clear Strip Size) resets the size of the Strip in NLA to match the chosen range of frames from Action; the second (Remap Start/End) resets the chosen range of Action frames to include all frame in the Action (this is only necessary if you are not using the new Locked Strip Length feature, and is useful for fixing older files or if you have "lost your place" when adding or subtracting frames from Actions). Both options are also in the Pulldown menu.
Other changes
- In Action and NLA editors: either left or right click now activates channels
- Added Theme Color for NLA strips
- Fixed selection issues in Action and NLA
- In Action and NLA editors: click-drag now 'grabs' the selection (as in other windows)
- In Action and NLA editors: using middle mouse button or scrollwheel on the left hand side of the window scrolls vertically.
Todo
- Adding Material/Lamp/Camera/Texture Ipos into the Action paradigm
- Move Shape Key sliders out of Action window, to become a more general slider option in Ipo Window.
- Thoroughly check timing in Blender again... Objects can have time offsets or time Ipos, a Scene can remap time, not to mention motion blur timing that needs to be kept track of!