Hello, everyone.  We are a small indie game studio called Drunken Monday.

We’ve recently made a game in Unity3d where you run around an arena, rotate around yourself with the huge axe and try to hit other players. Good smash - good kill.

We used ragdoll animation based on physics to make the deaths look more realistic. And everything was good in the beginning...

However, when the number of the characters and calculations started growing, the game began working slowly and lagging on older phones. Disabling all physics calculation gave us 50-60 fps and absolute smoothness, but we didn't want to give up the cool ragdoll deaths of the characters.
 
One of the solutions was to force the animators to build a pack of death animations. But we had a great idea to record a few ragdoll deaths directly in Unity and then just show the desired animation? Deaths will turn out to be diverse, there will no need to occupy animators, and the most important - everything will be fast, beautiful and realistic.

What we get:

Implementation

The animation clip in the Unity is presented by the AnimationClip class, which contains an array of AnimationCurve. AnimationCurve defines the curve for the changes of one particular property of a particular object, for example, the localPosition.x. Values change in the timeline are described by a number of Keyframe structures.

The idea is simple: for the each property of the each character object we create an AnimationCurve and store the values of this property on the curve for the each frame. The generated AnimationClip is exported through  AssetDatabase.CreateAsset at the end.

Let's create the class AnimationRecorderItem to track the each character object. All properties of the monitored object will be described through the dictionary, where the keys are the name of the properties and the values are the animation curves.

Properties = new Dictionary<string, AnimationCurve> ();
 
Properties.Add ( "localPosition.x", new AnimationCurve () );
Properties.Add ( "localPosition.y", new AnimationCurve () );
Properties.Add ( "localPosition.z", new AnimationCurve () );
 
Properties.Add ( "localRotation.x", new AnimationCurve () );
Properties.Add ( "localRotation.y", new AnimationCurve () );
Properties.Add ( "localRotation.z", new AnimationCurve () );
Properties.Add ( "localRotation.w", new AnimationCurve () );
 
Properties.Add ( "localScale.x", new AnimationCurve () );
Properties.Add ( "localScale.y", new AnimationCurve () );
Properties.Add ( "localScale.z", new AnimationCurve () );

For all of the object properties in each frame will be set their current values:

Properties["localPosition.x"].AddKey (new Keyframe (time, _animObj.localPosition.x, 0.0f, 0.0f));
Properties["localPosition.y"].AddKey (new Keyframe (time, _animObj.localPosition.y, 0.0f, 0.0f));
Properties["localPosition.z"].AddKey (new Keyframe (time, _animObj.localPosition.z, 0.0f, 0.0f));
 
Properties["localRotation.x"].AddKey (new Keyframe (time, _animObj.localRotation.x, 0.0f, 0.0f));
Properties["localRotation.y"].AddKey (new Keyframe (time, _animObj.localRotation.y, 0.0f, 0.0f));
Properties["localRotation.z"].AddKey (new Keyframe (time, _animObj.localRotation.z, 0.0f, 0.0f));
Properties["localRotation.w"].AddKey (new Keyframe (time, _animObj.localRotation.w, 0.0f, 0.0f));
 
Properties["localScale.x"].AddKey (new Keyframe (time, _animObj.localScale.x, 0.0f, 0.0f));
Properties["localScale.y"].AddKey (new Keyframe (time, _animObj.localScale.y, 0.0f, 0.0f));
Properties["localScale.z"].AddKey (new Keyframe (time, _animObj.localScale.z, 0.0f, 0.0f));

But if you record all values for the each frame for the each property of the each object, the output file of the animation will turn out to be too large. Let's introduce the conditions for limiting the minimum changes in comparison with the previous frame. If the object has moved, increased and turned just a little bit, we will not record these changes.

Completed class: AnimationRecorderItem.cs

Also, we have to create a manager class AnimationRecorder.

This script should be executed through the all children of the animated object and create an instance of AnimationRecorder for each of them.
And also immediately generate and remember relativePath under which it will be saved in AnimationClip.

According to the documentation,  relativePath is generated as follows:

Quote

Path to the game object this curve applies to. The relativePath is formatted similar to a pathname, e.g. "root/spine/leftArm". If relativePath is empty it refers to the game object the animation clip is attached to.

The code will look like:

private List<AnimationRecorderItem> _recorders;
 
void Start ()
{
    Configurate ();
}
 
void Configurate ()
{
    _recorders = new List<AnimationRecorderItem> ();
 
    var allTransforms = gameObject.GetComponentsInChildren< Transform > ();
    for ( int i = 0; i < allTransforms.Length; ++i )
    {
        string path = CreateRelativePathForObject ( transform, allTransforms [ i ] );
        _recorders.Add( new AnimationRecorderItem ( path, allTransforms [ i ] ) );
    }
}
 
private string CreateRelativePathForObject ( Transform root, Transform target )
{
    if ( target == root )
    {
        return string.Empty;
    }
 
    string name = target.name;
    Transform bufferTransform = target;
 
    while ( bufferTransform.parent != root )
    {
        name = string.Format ( "{0}/{1}", bufferTransform.parent.name, name );
        bufferTransform = bufferTransform.parent;
    }
    return name;
}

To calculate current animation time and record the properties values for the each frame:

private float _recordingTimer;
private bool _recording = false;
 
void Update ()
{
 
    if ( _recording )
    {
        for ( int i = 0; i < _recorders.Count; ++i )
        {
            _recorders [ i ].AddFrame ( _recordingTimer );
        }
        _recordingTimer += Time.deltaTime;
    }
}

But the  Update function is called quite often and recording the animation every frame is pretty redundant, so we limit the record. 30 fps should be enough for everyone. 
We will start recording by tapping on Spacebar.

private const float CAPTURING_INTERVAL = 1.0f / 30.0f;
 
private float _lastCapturedTime;
private float _recordingTimer;
private bool _recording = false;
 
void Update ()
{
    if ( Input.GetKeyDown ( KeyCode.Space ) && !_recording )
    {
        StartRecording ();
        return;
    }
 
    if ( _recording )
    {
        if (_recordingTimer==0.0f||_recordingTimer-_lastCapturedTime>=CAPTURING_INTERVAL)
        {
            for ( int i = 0; i < _recorders.Count; ++i )
            {
                _recorders [ i ].AddFrame ( _recordingTimer );
            }
            _lastCapturedTime = _recordingTimer;
        }
        _recordingTimer += Time.deltaTime;
    }
}
 
public void StartRecording ()
{
    Debug.Log ( "AnimationRecorder recording started" );
    _recording = true;
}

Let’s implement an animation export. We will create the AnimationClip instance and fill it with the collected values.

private void ExportAnimationClip ()
{
    AnimationClip clip = new AnimationClip ();
    for ( int i = 0; i < _recorders.Count; ++i )
    {
        Dictionary<string,AnimationCurve> propertiles = _recorders [ i ].Properties;
        for ( int j = 0; j < propertiles.Count; ++j )
        {
            string name = _recorders [ i ].PropertyName;
            string propery = propertiles.ElementAt ( j ).Key;
            var curve = propertiles.ElementAt ( j ).Value;
            clip.SetCurve ( name, typeof(Transform), propery, curve );
        }
    }
    clip.EnsureQuaternionContinuity ();
 
    string path = "Assets/" + gameObject.name + ".anim";
    AssetDatabase.CreateAsset ( clip, path );
    Debug.Log ( "AnimationRecorder saved to = " + path );
}

Completed class AnimationRecorder.cs

Finally, we will create the  AnimationRecorderRagdollHelper helper class, which function will stop the Animator on the animated object, turn on all collisions, give the object acceleration and start recording our animation. The end of the animation recording will be completed by ourselves. 
To avoid some artefacts due to scene loading and the initialization of various objects, the script will start working with the specified delay.
 

Completed class AnimationRecorderRagdollHelper.cs
  
That's all, we add AnimationRecorderRagdollHelper on our character, set the impact force, then start the scene - and watch how the character cheerfully flies around the scene.

When the cold corpse freezes on the ground - press Spacebar. 

The script will export our animation to the root of the project.

https://gfycat.com/RecklessFickleBarracuda

We recorded 4-5 animations for each character in this way and choose between them randomly when the character dies.
 
P. S. Or not quite randomly.
Our game is multiplayer, physics is calculated on the server and the vector of impact comes to us. So we select the necessary animation based on the vector which comes to us from the server, simply looking for the closest vector which the animation was recorded.
 
Links:
Project on GitHub

Slash Arena: Online ( Facebook )

Slash Arena: Online ( Steam )