Up to no now, adding multiple actions in NLA with walkcycles required to animate them standing still, as if walking on a conveyor belt. The stride option then makes the object itself move forward, trying to keep the foot stuck on the floor (with poor results!).

This option now allows to make walk cycles moving forward. By indicating a reference Offset Bone, the NLA system will use that bone to detect the correct offset for the Armature Pose to make it seamlessly going forward.

Best of all, this option works as for cyclic Action Strips as well as for individual Action Strips. Note that for individual strips, you have to set the strip on "Hold". (Might become automatic detected later).

Here's an example edit image for NLA:
www.blender.org/bf/nla_match-cycle.jpg

And the animation for it:
download.blender.org/demo/test/2.43/0001_0150_match.avi

Blender file:
download.blender.org/demo/test/2.43/mancandy_matching.blend

Using this kind of cycling works pretty straightforward, and is a lot easier to setup than Stride Bones.

To be further tested:
- Blending cycles
- matching rotation for the bones as well.

Typically walk cycles are constructed with certain Bones to be the handles, controlling for example the torso or feet.

An Action Modifier allows you to use a Curve Path to deform the motion of these controlling bones. This uses the existing Curve Deformation option. Modifiers can be added per Action Strip, each controlling a channel (bone) by choice, and even allows to layer multiple modifiers on top of each other (several paths deforming motion). This option is using the dependency graph, so editing the Curve will give realtime changes in the Armature.

The previous walkcycle, controlled by two curves:
download.blender.org/demo/test/2.43/0001_0150_deform.avi

Blender file:
download.blender.org/demo/test/2.43/mancandy_actiondeform.blend

Another demo avi:
download.blender.org/demo/test/2.43/0001_0120_deform.avi

Two identical paths, but one controlled with a speed curve
download.blender.org/demo/test/2.43/0001_0150_speed.avi

Action Modifiers can be added in the NLA Properties Panel. Per Modifier you have to indicate the channel and a Curve Object. You can copy modifiers from one strip to another using CTRL+C (only copies to active Object strips).
 

Setting up a correct Curve Path has to be carefully done:

• Use SHIFT+A "Curve Path" in top view, or ensure the path is not rotated.
• Make sure the center point of the Curve Object is at the center of the Armature (or above)
• Move the first point of the curve to the center point as well.
• Check if the path starts from this first point, you can change it using (in Curve EditMode) the option Wkey -> "Switch Direction"
• Make sure alignment uses the correct axis; if the Armature walks into the negative Y direction, you have to set in Object Buttons, "Anim settings" Panel, the correct Track option. (Note; option will probably move to the Modifier later).
• Paths can be used to fully rotate a bone, or only for specific axes. For example a body bone should only rotate in XY, not Z. You can set this in the NLA Properties Panel as well.
• By default Curve Paths are added with a smooth Speed Ipo Curve. Open an Ipo Curve Editor, set it to show "Speed" and change this to linear for example by removing the curve entirely.
• Speed Ipos map by default the horizontal 0-100 range to the full path length, since there's no actual time relationship here.

This is a good reason to make such paths automatic (on a command). Is on the todo list.

Also note this:

• The Curve Path extends in beginning and ending, that's (for now) the default, and allows to use multiple paths. Make sure paths begin and end horizontal.
• Moving the Curve in Object Mode will change the "mapping" (as if the landscape a character walks over moves). Moving the Curve in Edit Mode will change the actual position of the deformation.
• The Curve "Stretch" deform option doesn't work.
• Modifiers are executed *after* all actions in NLA are evaluated, there's no support yet for blending multiple strips with Modifiers.
• This doesn't work yet for time-mapping...

 
The current code is still for review by character animators... some details or
working methods might change.
This feature can also be used for other modifiers, such as noise (Perlin) or
the mythical "Oomph" (frequency control) and of course Python.

Special thanks to Bassam & Matt for research & design review.