From BlenderWiki
Action
- An action is a generic container containing various IPO blocks.
- IPO blocks are contained in Action Channels.
- Action Channels are named, so that users of the Action can retrieve their respective anim data from the right IPO block.
- Action Channels may have Constraint Channels attached, which affect the Constraints of Object or Pose Channels (bones)
Action Editor
- The Action Editor is where Actions are edited. It is also where the majority of keyframing editing takes place (tweaking/refining of keyframes occurs in IPO editor).
- It is equivilant to the dopesheet in many other programs.
- There can be several 'modes' like in the IPO editor, so that multiple sets of action/keyframe data can be edited. This means that when an Object is active, you are not restricted to only editing that Object's ob-action. This means that you can choose to edit keyframes from 'IPO-blocks' revelant to the chosen mode.
NLA Editor
- The NLA Editor is where Actions/ShapeKeys are combined/mixed in a non-destructive, non-linear way.
- You can only work with strips representing the Actions/Shapekeys, but not the individual keyframes.
- Each block/folder shown in the NLA editor, can get a series of tracks. Tracks are used when overlapping of strips needs to occur. Multiple strips can occur in one track as long as they don't overlap each other.
- For each strip, there are specialised curves to control the strength of blending between strips, and also of the timing.
- You can choose to: tempolarily disable a track(s) or strip(s), only play one strip/track, or stop a strip/track from being edited.
- Each datablock-type has it's own set of NLA data (i.e. Object-Level and Pose-Level NLA-mixing for an Armature are kept separate). This is because mixing actions from different blocktypes is simply not logical.
