Add TimeTimingModel.

Assets/Cryville/Crtr/Chart.cs

@@ -16,6 +16,11 @@ namespace Cryville.Crtr {
 			n = _n;
 			d = _d;
 		}
+		public BeatTime(int _n, int _d) {
+			b = _n / _d;
+			n = _n % _d;
+			d = _d;
+		}
 
 		[JsonIgnore]
 		public int b;

Assets/Cryville/Crtr/Extensions/TimingModel.cs

@@ -39,4 +39,16 @@ namespace Cryville.Crtr.Extensions {
 			return new BeatTime(i, n, d);
 		}
 	}
+	public class TimeTimingModel : TimingModel {
+		public TimeTimingModel(double offset = 0) : base(offset) { }
+		public void ForwardTo(double t) {
+			if (t == Time) return;
+			if (BPM == 0) throw new InvalidOperationException("BPM not determined");
+			BeatTime += (t - Time) * BPM / 60;
+			int n, d;
+			FractionUtils.ToFraction(BeatTime, 1f / 48 / BPM * 60, out n, out d);
+			FractionalBeatTime = new BeatTime(n, d);
+			Time = t;
+		}
+	}
 }