Mix Clips 1D Node

The Mix Clips 1D animation controller node is used to linearly interpolate between a fixed set of animations.

Every animation clip has a position value in 1D space. The lerp input pin value determines how to interpolate those clips. The output pose will be either exactly one of those clips, or a mix between two clips, but never more than that.

So if one clip is placed at position 0 and another at position 1, you can fade from the first clip to the second by passing in a lerp value between 0 and 1.

The length of each clip may be different, however, the lookup positions across all clips are synchronized. That means if two clips are being mixed, and the first clip is sampled right at its middle, then the second clip will also be sampled at its middle, even if this is a completely different time offset (say 1 second versus 1.5 seconds). At which speed to move the sample position forwards, is determined by the length of the two animation clips that the lerp value is closest to.

This node is useful if you have an action that can be done at different speeds and you want to cover all possible speeds with just a few different animation clips. The most intuitive example is a walk/run motion. You only need two animation clips, one for slow walking and one for fast running, and this node allows you to generate any speed in between through interpolation.

For this to work, all animation clips have to follow the rule that they do the same motion at the same relative time offset. So in the case of a walk/run motion, both clips have to start with the same foot forwards, then move the other foot and finally move the first foot again, such that the animation is looped. The clips can have different lengths, though, so the run clip might be shorter than the walk clip (and therefore faster).

In the video above you can see such a transition in action. The lerp input value is varyied to demonstrate how the resulting interpolated animation looks. Here the node also has an idle and a walk backward clip, so it can interpolate between even more states.