Wednesday, September 23, 2009

Neutral Walk Cycle 01 - Keyframes Explained


I finally bothered myself to log into windows and break down yesterday's walk cycle frame by frame. Like I said in the last post, the four main keyframes in a walk cycle are contact, down, passing and up positions. Now, before I begin, I'd like to mention that everything I've learned is mostly from reading. Mainly from Richard William's "Animator's Survival Kit", which is all your animation answers in one handy animation bible of godliness, and websites such as which is written by an "angry animator" man called Dermot O'Conner who not only talks you through animation basics but has lots of lovely flash animation to demonstrate what it is he's explaining. These beautiful sources have taught me that a walk cycle has, as I mentioned before, 4 main keyframes per step (gait). If it had been up to my own observations, I would have guessed it at 3. This is why I am still noob.

So here they are as I have come to learn them, starting firstly with mr. contact position:

Contact position is, as you may guess, when the "leading foot" (in this case the right foot) makes contact with the ground. It's usually a pretty good place to start with a walk. At this point feet are at their furthest apart in the cycle, with the left foot about to leave the ground and the right foot about to take the weight. The arms always work in opposition to the leg, so here because the right leg is forward the right arm is back, and vice versa. This helps to balance the character and propel them forward into the next step.

The next keyframe is down position:

Here the right foot is flat on the floor taking the weight as the left foot is just about to leave the ground and make it's way forward. This is where the body reaches it's lowest point as the front leg is bent "catching" all the weight of the step. Also, since the arms are always a beat behind the legs, it is at this position, and not the contact position, that the arms are at their furthest apart.

After that we have the passing position where the legs and arms pass each other and the body. Here the leading leg (right) becomes the trailing leg and vice versa. Same goes for the arms. Here, because the right leg is straight and directly beneath the body, holding it's weight, the body is lifted up, so in this position the body is more raised than in contact position. Finally, the left foot, although you can't see it very well in this drawing, will pass only centimeters over the ground because, since we're such sensible beings, we naturally want to conserve energy we only lift the foot as high off the ground as we need to. This is why we stumble and trip so often.

The final keyframe is the up position:

The trailing foot (right) pushes off the floor propelling the character forward and stretching the body to it's tallest point in the cycle. The body leans into the next step, and the leading (left) foot is thrown forward to "catch" the body as it "falls" into it's next step.

Now, these are only the keyframes for one step. The second step would obviously be the same keyframes but the legs and the arms are the other way round. After that it loops and hey presto you have a basic keyframed walk cycle! Huzzah!

So having done all my keyframes and all my inbetweens (I resorted to only one inbetween, instead of two making the cycle 16 frames in total and not 24) here is the final .avi:


The main adjustments I was thinking of making were sorting out the expanding/shrinking feet and shoulder problem, stopping the hip "pop" and fixing the arms when they're at their furthest apart (they seem to hover a bit). I also want to add in more of a shoulder movement, so that when the arm is forward the shoulder is forward, that kinda thing. As of right this very minute I'm redrawing the keyframes for walk cycle 2 (walk harder) inbetween typing this up. I've fixed the feet and hip problem and I'm about to move onto the shoulders, then arms last. I'm aiming to have it inbetweened and line tested tomorrow, hopefully in time for a mini group crit.

After that we move from the skeleton (or android as Craig calls it) to a more fuller-figured maquette.

Till then.

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