Week 4: Big Dog Animation

 i)        If engineered or programmed badly, BigDog would fall over. Watch the full video again, and describe how BigDog’s legs move while walking– ie. what is the sequence of leg movements for one complete step? Use the terms BL, BR, FL, and FR for the back-left, back-right, front-left and front-right legs.

     The Big Dog starts by moving its FL foot and BR foot simultaneously at the direction it was being pushed. This was done to maintain balance and to prevent the whole body from tipping over. After one step, the opposite legs (FR and BL) will move and this sequence will repeat until it regained its balance. As it raised its leg, the body raised slightly and dropped when the leg touches the ground. Needless to say that body is tilted due to gravity pulling it down as it lost its balance.

ii)       Explain how this sequence of movements manages to balance BigDog’s body weight.

      The moving leg acts as a form of a support for the body as the angle and the impact upon the ground stops the body from tipping over immediately. Hence, the lack of balance reduces with each step, eventually coming to a halt when balance is retained.

iii)     Look at BigDog_kick_slow_motion.mov. Draw a storyboard of BigDog stabilising itself after being kicked.

You should draw the key poses. You don’t need to draw well – but you must show the leg positions and the body rotations around the X, Y and Z axes for each key pose.

Starting from the left, the first keypose is when the Big Dog is standing still. The second keypose is when the one frontal leg and the opposite back leg is raising. The body rotated  and raised slightly and, though mechanical, the legs move in the arc. The rest of the legs remain still. On the third keypose, the moving legs touches the ground and the body lowered slightly. The second and third keyposes repeat with the body rotation gradually reducing. Eventually, the final frame would be the first keypose to show that it has regained balance.

The following are a pair of videos displaying a Big Dog model animated to resemble the original video:

Making the animation is deceptively hard as I made a total of 7 retries. The difficulty mostly comes from showing the weight in the movement of Big Dog and to show the lack of balance. This was achieved through rotation and up-and-down movement of the body. I am ultimately proud of my work as I worked very hard for it.