Quadruped Animation

Animating in 3D now. I studied the differences in quadruped walks and runs, and watched a tutorial by animator Felix Sputnik on Vimeo talking about animating quadrupeds.

When the rear legs touch the ground, the animal is at tits shortest, with the curved body acting as a spring of stored energy. The legs can only push, so the moment the rear legs touch the ground (contact is made), the leg push the body forward. The animal makes most use of this by extending the body against the push of the legs. Gaining forward momentum. The front legs keep the momentum going, allowing the animal to be at its longest. When the front legs leave he ground, the animal is un-propelled. No FORWARD force can happen. They are in “flight” essentially. It uses this time effectively, by reloading its spring and bending its spine again, to prepare for the next push. The force flows from the rear to the front. If you could see it on a page, the curvature of the spine would be skin to the at of a Sine curve, moving through the animal from rear to the front. This is the propagation of force. It moves through the animal faster than the actual animal moves. The feet are stationary when on the ground, but the wave travelling through the animal needs to be faster, so that the legs can overtake the body to get in front of it; and so get ready for the next push. Canine feet patterns have the front leg pattern hit the ground in a left-right fashion. The rear legs hit the ground in a right-left fashion.

I went into Maya and began animating with the cycle in mind. Because I knew that we would see the jungle cat from the side view, I arranged the camera this way, and animated according to the camera. This was also a favorable situation for me to be in, because it meant that everything on the jungle cat’s right hand side, would not be seen by the camera. I just had to make sure that I was able to animate it in such a way that made it look like a big cat in the real world. The reference footage, and the research I had done up until this point had been for this purpose.

 

After putting together the main keyframes, I put the keys to auto splines in the graph editor, in order to be able to see how the motion looked when animated, rather than in stepped splines.

 

At this current stage after my animation, I was able to receive some feedback from my tutors regarding the posing and what I can do in order to improve the motion of the run cycle.

 

In order to improve the animation, it was pointed out to me that:

• The arcs of the feet as they run not obvious enough. It looks as though the leopard is kicking its feet out to glide, rather than rising its feet to spring out after the rear legs have made contact with the ground.
• The trajectory of the head and shoulders is quite linear throughout the animation. It looks as though the body is moving on quite a robotic fashion, so fix this by raising the head, or lowering the rest of the body so that there is a clear and defining arc running along the back of the spine of the animal.
• The feet land together upon contact with the ground. You have already made the steps to offset the front legs, so make the offset larger in the rear legs also. Look back at the reference footage and make comparisons using angle sighting to the angles and trajectories of the different parts of the body compared to others. This will help to ensure that you have made it so the offset is defined enough, and that the body does not become off balance when the rear legs move in to make contact. As it stands now, the next motion could show the leopard falling onto its face.

 

 

With these changes in mind, I made some more tweaking to the run cycle within Maya, making sure to utilise the motion trail options box to attach motion trails to different controls on the rig and make it so I can have greater control over how the arcs are formed for these parts of the body. I went back to the keyframes I made also, and matched them up with the footage, so that I may see how I could improve the posing of the character more.

 

• The offsetting of the feet look better, but there seems to be this knick before it begins the next cycle. More tweaking adjustments should be made in order to make that motion a lot smoother.

 

The motion itself looks much smoother now, as you can see from above clip. Matching up the keyframes with stronger keyposes from the reference footage allowed me to break the rig in certain instances as well to really exaggerate the stretch outwards the cheetah takes in the reference footage. I lucked out slightly in that respect, as I only need the silhouette for my final piece. I was able to translate the IK rig handles (which normally you shouldn’t do) in order to achieve this pose. One thing I also did was bake the animation after turning on post infinity in the graph editor. This was more useful to me than copying and pasting the keyframes, as sometimes, it would cause a control on the rig to continuously translate in one of the directional axes instead of continuing on with the same animation.