/// <summary>
/// Computes keyframe times to ensure a constant speed along the given spline.
/// </summary>
/// <remarks>
/// If the speed is 0 or omitted, it will be auto-computed so the animation completes in 1s.
/// </remarks>
public static float[] ComputeSplineTimes(Vector3[] positions, float speed = 0f)
{
bool isUnitLength = (speed == 0f);
if (isUnitLength)
speed = 1f;
int frameCount = positions.Length;
float[] times = new float[frameCount];
times[0] = 0f;
if (frameCount < 4)
{
for (int i = 1; i < frameCount; ++i)
times[i] = times[i - 1] + (positions[i] - positions[i - 1]).magnitude / speed;
}
else
{
times[1] = (positions[1] - positions[0]).magnitude / speed;
int samplesPerSegment = 16;
Vector3 oldPosition = positions[1];
for (int j = 2; j < frameCount - 1; ++j)
{
SplineSegment segment = new SplineSegment(positions[j-2], positions[j-1], positions[j], positions[j+1]);
float segmentLength = 0f;
for (int i = 0; i < samplesPerSegment; ++i)
{
float t = (float)i / (float)(samplesPerSegment - 1);
Vector3 position = segment.GetPosition(t);
segmentLength += (position - oldPosition).magnitude;
oldPosition = position;
}
times[j] = times[j-1] + segmentLength / speed;
}
float endDistance = (positions[frameCount - 1] - positions[frameCount - 2]).magnitude;
times[frameCount - 1] = times[frameCount - 2] + endDistance / speed;
}
if (isUnitLength)
{
float totalTime = 0f;
foreach (float time in times)
totalTime += time;
for (int i = 0; i < times.Length; ++i)
times[i] /= totalTime;
}
return times;
}
