The Evaluate function on an animation curve gets a value at a time.

https://docs.unity3d.com/ScriptReference/AnimationCurve.Evaluate.html

But it's not clear (to me) what time base or units are used.

For ParticleSystem.MinMaxCurve, this is explicitly described as being evaluated as a normalised 0 to 1 range of values of the curve's duration:

https://docs.unity3d.com/ScriptReference/ParticleSystem.MinMaxCurve.Evaluate.html

Normalized time (in the range 0 - 1, where 1 represents 100%) at which to evaluate the curve. This is valid when ParticleSystem.MinMaxCurve.mode is set to ParticleSystemCurveMode.Curve or ParticleSystemCurveMode.TwoCurves.

CodePudding user response：

It uses 0 to 1 in the most cases but depends completely how you configure and use yours ... you can easily extend an AnimationCurve with keyframes before 0 and beyond 1.

You can however get the duration of your AnimationCurve so basically you can normalize down any animation curve to a "time" value between 0 and 1 using

public static class AniamtionCurveUtils
{
    public static float EvaluateNormalizedTime(this AnimationCurve curve, float normalizedTime)
    {
        if(curve.length <= 0)
        {
            Debug.LogError("Given curve has 0 keyframes!");
            return float.NaN;
        }

         // get the time of the first keyframe in the curve
        var start = curve[0].time;

        if(curve.length == 1) 
        {
            Debug.LogWarning("Given curve has only 1 single keyframe!");
            return start;
        }

        // get the time of the last keyframe in the curve
        var end = curve[curve.length - 1].time;
       
        // get the duration fo the curve
        var duration = end - start;
        
        // get the de-normalized time mapping the input 0 to 1 onto the actual time range 
        // between start and end
        var actualTime = start   Mathf.Clamp(normalizedTime, 0, 1) * duration;

        // finally use that calculated time to actually evaluate the curve
        return curve.Evaluate(actualTime);
    }
}

and then e.g.

var someValue = someCurve.EvaluateNormalizedTime(someNormalizedTime);