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Track.cs
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Track.cs
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using System;
using System.Collections.Generic;
using System.IO;
namespace RocketNet
{
/// <summary>
/// GNU Rocket track object. You can query values with it.
/// </summary>
public class Track
{
/// <summary>
/// Retrieve track value for a certain point in time
/// </summary>
/// <param name="row">Current row (floating point because time is continuous and in flux and shit)</param>
/// <param name="sinceRows">Difference of current row and the row of the preceding keyframe</param>
/// <returns>Track value for given row</returns>
public float GetValue(float row, out float sinceRows)
{
// If we have no keys at all, return a constant 0
if (keys.Count == 0)
{
sinceRows = row;
return 0.0f;
}
// find key at/before the current row
var irow = (int)Math.Floor(row);
var idx = FindKey(irow);
if (idx < 0)
idx = -idx - 2;
// at the edges, return the first/last value
if (idx < 0)
{
sinceRows = row - keys[0].row;
return keys[0].value;
}
if (idx > keys.Count - 2)
{
sinceRows = row - keys[keys.Count - 1].row;
return keys[keys.Count - 1].value;
}
// interpolate according to key-type
float t = (row - keys[idx].row) / (keys[idx + 1].row - keys[idx].row);
switch (keys[idx].type)
{
case Key.Type.Step:
t = 0;
break;
case Key.Type.Smooth:
t = t * t * (3 - 2 * t);
break;
case Key.Type.Ramp:
t = (float)Math.Pow(t, 2.0);
break;
}
sinceRows = row - keys[idx].row;
return keys[idx].value + (keys[idx + 1].value - keys[idx].value) * t;
}
/// <summary>
/// Retrieve track value for a certain point in time
/// </summary>
/// <param name="row">Current row (floating point because time is continuous and in flux and shit)</param>
/// <returns>Track value for given row</returns>
public float GetValue(float row)
{
float dummy;
return GetValue(row, out dummy);
}
// find key at or after the given row
int FindKey(int row)
{
int lo = 0;
int hi = keys.Count;
// binary search, t->keys is sorted by row
while (lo < hi)
{
int mi = (lo + hi) / 2;
if (keys[mi].row < row)
lo = mi + 1;
else if (keys[mi].row > row)
hi = mi;
else
return mi; // exact hit
}
// return first key after row, negated and biased (to allow -0)
return -lo - 1;
}
// create/set a key
internal void SetKey(Key key)
{
int idx = FindKey(key.row);
if (idx < 0)
{
// no exact hit, we need to allocate a new key
idx = -idx - 1;
keys.Insert(idx, key);
}
else
keys[idx] = key;
}
// delete a key
internal void DeleteKey(int row)
{
int idx = FindKey(row);
if (idx < 0) throw new InvalidOperationException("key not found");
keys.RemoveAt(idx);
}
// load track from a stream
internal void Load(Stream s)
{
using (var br = new BinaryReader(s))
{
int nKeys = br.ReadInt32();
keys.Clear();
keys.Capacity = nKeys;
for (int i = 0; i < nKeys; i++)
{
int row = br.ReadInt32();
float value = br.ReadSingle();
int type = br.ReadByte();
keys.Add(new Key
{
row = row,
value = value,
type = (Key.Type)type,
});
}
}
}
// save track to a stream
internal void Save(Stream s)
{
using (var bw = new BinaryWriter(s))
{
bw.Write((Int32)keys.Count);
foreach (var key in keys)
{
bw.Write((Int32)key.row);
bw.Write((Single)key.value);
bw.Write((byte)key.type);
}
}
}
internal struct Key
{
public enum Type
{
Step = 0, // stay constant
Linear = 1, // lerp to the next value
Smooth = 2, // smooth curve to the next value
Ramp = 3, // quadratic curve to the next value (ease-in)
}
public int row;
public float value;
public Type type;
}
internal string name;
private List<Key> keys = new List<Key>();
}
}