Importing animations

The Dead Keys game features character animations for the zombies, namely walk, fight, and idle. These are included as FBX files. They can be imported into the Animations folder. The animations themselves are not intended for or targeted toward the zombies, but Mecanim's Humanoid Retargeting lets us reuse almost any character animations on any humanoid model. Let's now configure the animations. Select each animation and switch to the Rig tab. Choose Humanoid for the Animation Type, and leave the Avatar Definition at Create From This Model:

Now, move to the Animations tab. Enable the Loop Time checkbox to enable animation looping for the clip. Then, click on Apply. We'll have good cause to return to the animation settings in the later chapters, for further refinement, as we'll see:

Now, let's explore a common problem with loopable walk animations that have root motion encoded. Root motion refers to the highest-level of transformation applied to an animated model. Most bone-based animation applies to lower-level bones in the bone hierarchy (such as arms, legs, and head), and this animation is always measured as relative to the topmost parent.

However, when the root bone is animated, it affects a character's position and orientation in world space. This is known as root motion. One problem that sometimes occurs with imported, loopable walk animations is a small deviation or offset from the neutral starting point in its root motion. This causes a mesh to drift away from its starting orientation over time, especially when the animation is played on a loop. To see this issue in action, select the walk animation for the zombie character, and from the object Inspector, preview the animation carefully. As you do this, align your camera view in the preview window in front of the humanoid character and see how, gradually, the character's walk deviates slowly from the center line on which he begins. This shows that, over time, the character continually drifts. This problem will not just manifest in the preview window, but in-game too:

This problem occurs as a result of walk-cycle inaccuracies in root motion. By previewing the Average Velocity field in the object Inspector, you'll see that the X motion field is a non-zero value, meaning that offset occurs to the mesh in X. This explains the cumulative deviation in the walk, as the animation is repeated:

To fix this problem, enable the Bake Into Pose checkbox for the Root Transform Rotation section. This lets you override the Average Velocity field. Then, adjust the Offset field to compensate for the value of Average Velocity. The idea is to adjust Offset until the value of Average Velocity is reset to 0, indicating no offsetting. Then, click on Apply: