5: Basic Walk Action - 30 Frames of Strolling

When you consider that it takes a human in the neighborhood of 12-18 months to learn to walk, the fact that we're going to teach this creature to walk in just a few short minutes is nothing short of spectacular.

Step 1: Go to the PWS (Project Workspace) and click on Actions. Now Right Click on it. A menu will popup. Select New Action. Next you'll need to select which model this action will apply to. Select HeadSeg. If all goes well, you should have a new window pop up called Action1, looking something like this:

Before we go further, let's take a look at a classic walk cycle, as illustrated by Preston Blair:

Now we're going to take a look at a modified cycle that I cribbed from these images and annotated:

This cycle is shorter (has fewer actual images) and runs from 0 to 30. These will become the frames in our walk. I've called out frames 0, 7, 14, 21 and 30 for specific reasons. 0 and 30 are copies of the same pose (for reasons we'll go in to later). 14 is the opposite (left leg back, right forward) of 0/30. 7 and 21 represent intermediate poses between the other two extremes. The unspecified frames will be filled in (interpolated or 'tweened') by A:M.

30 is a copy of 0 because this will be a 30 frame cycle and if we cycled from 0 around to 30 then back to 0, we'd see a hitch as we hit 30 then 0 (which are the same pose). If instead, we go from 0 to 29 (30 frames) then repeat, we should get a fluid, repeating walk cycle.

With all that in mind, let's make a cycle.

Step 2 (we had Step 1 earlier): Pose the HeadSeg in Action1 something like Frame 0 above. For me, this was most easily done by grabbing the top of the knee (between the upper and lower leg) and dragging the knee forward. This will leave the end of the lower leg to behind, so now grab it and position it as needed by switching between the views. Do this for both legs and you should end up with somthing like (from the top) this:

Once you are satisfied that this looks good (check all the views) hit the Keyframe button. It's a small Key shaped icon near the bottom. Since we're going to need this frame later, let's copy it by going to the Edit menu and selecting Copy Keyframe.

Step 3: Now, go to the current frame field (it should now read 00:00:00 if you use SMTP, if you are going by frames, it might read simply '0'), click in it and delete the current value and type '30'. We now want to paste our Keyframe from frame '0', so go to the Edit menu again and choose Paste KeyFrame.

Step 4: Go back to the current frame field and enter '14' to go to frame 14. Referring to our walk cycle above, in this frame we want it to be the opposite of frames 0/30. Pose this frame accordingly.

If you scrub using the frame tool between frame 0 and 30 now, you'll see the start of our cycle. It's pretty boring, though, since the feet will likely just slide along the ground, not very realistically and, worse yet, not very interestingly.

Step 5: Now go to frame '7'. This is intermediate between the extreme poses from frame 0 and 14. Note that in addition to the change in the legs, the head level has changed as well, popping up as it transitions from 0 to 14. Do the same for frame 21, as it transitions from 14 to 30.

Step 6: Again, scrub through the walk. You should see a much more interesting walk, with the body going up and down, legs going through the cycle in a much more natural way. With only 5 keyframes (one of which is a copy) we've got a workable walk cycle. If everything has gone as expected, you should see a PWS that looks something like this:

Some items to note from the screen shot:

Note that only the bones that changed (the Body, upper and lower legs) get captured in the Keyframe
Note the Keyframes at 0, 7, 14, 21 and 30.
This is the Keyframe button. It's a little key!
This is the scrub bar
This is the current frame field

Here's a cool thing to keep in mind with regards to reusing actions. Since we only keyframed bones that exist in both the HeadSeg and BodySeg, any action that we make that only uses bones shared between those two models will work in both models. So, not only did we create a walk cycle for the HeadSeg, we also created one that will work just as well for the BodySeg.

Now, if we were to use this Action in a choreography as-is, we would apply it to a model, indicate how many times we want it to repeat over what range of time and be good. Rather than do that, we're going to use Stride Length, a nifty feature of the Action, to take care of applying the correct number of cycles over the (physical) length of the path it will eventually walk.

In the Action's General Properties panel, click in the box that says "Stride Length". Once you do that, you should see a grid appear in the Action window. This is used to determine the length of the stride. In the case of my model, the stride length turned out to be 2.71. Stride length is great to keep your model from appearing to "skate" or slide across the ground as it walks. For a tutorial dedicated to Stride Length, try this: PuttyDude Walking on a Path.

Now that the Action is done, let's click on Action1, hit F2 and rename it to Walk.

Now, let's build a simple Choreography to perform in.

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