Mirrored Animations

[lubomirkurcak]

Humanoid characters usually have mirrored bones like lowerarm.l and lowerarm.r.

It would be useful to be able to play mirrored animations where animation targets for these bones are swapped.

Here's how I imagine the process could go:

1. During asset loading, animations can be specified to be loaded as mirrored
   • The mirror axis needs to be specified: X, Y, Z
2. If the animation was specified to be mirrored:
   • Animation targets for matching bones .*\.[rl] are swapped
   • All animation curves are mirrored along the specified axis

Some considerations:

• Bone names are only present during asset loading
  • we can transform animations during loading and treat them as separate assets
• Curves need to be mirrored along a specific axis based on which way the character is facing
  • not hard to figure out correct axis by trial and error
• Animation curves need to be able to be mirrored

How the API could work:

Labeling

pub enum GltfAnimationMirrorAxis {
    X,
    Y,
    Z,
}

pub enum GltfAssetLabel {
    // ...
    Animation(usize),
    MirroredAnimation(usize, GltfAnimationMirrorAxis),
    // ...
}

Usage

asset_server.load(GltfAssetLabel::Animation(0).from_asset(asset_name)),
asset_server.load(GltfAssetLabel::MirroredAnimation(0, GltfAnimationMirrorAxis::X).from_asset(asset_name)),
asset_server.load("asset.glb#Animation0");
asset_server.load("asset.glb#MirroredAnimationX0");