} // End of Slerp()
//-------------------------------------------------------------------------------
// @ ApproxSlerp()
//-------------------------------------------------------------------------------
// Approximate spherical linear interpolation of two quaternions
// Based on "Hacking Quaternions", Jonathan Blow, Game Developer, March 2002.
// See Game Developer, February 2004 for an alternate method.
//-------------------------------------------------------------------------------
public IvQuat ApproxSlerp(ref IvQuat start, ref IvQuat end, float t)
{
float cosTheta = start.Dot(end);
// correct time by using cosine of angle between quaternions
float factor = 1.0f - 0.7878088f * cosTheta;
float k = 0.5069269f;
factor *= factor;
k *= factor;
float b = 2 * k;
float c = -3 * k;
float d = 1 + k;
t = t * (b * t + c) + d;
// initialize result
IvQuat result = t * end;
// if "angle" between quaternions is less than 90 degrees
if (cosTheta >= ML.Util.kEpsilon)
{
// use standard interpolation
result += (1.0f - t) * start;
}
else
{
// otherwise, take the shorter path
result += (t - 1.0f) * start;
}
return(result);
} // End of ApproxSlerp()
} // End of Lerp()
//-------------------------------------------------------------------------------
// @ Slerp()
//-------------------------------------------------------------------------------
// Spherical linearly interpolate two quaternions
// This will always take the shorter path between them
//-------------------------------------------------------------------------------
public IvQuat Slerp(ref IvQuat start, ref IvQuat end, float t)
{
// get cosine of "angle" between quaternions
float cosTheta = start.Dot(end);
float startInterp, endInterp;
// if "angle" between quaternions is less than 90 degrees
if (cosTheta >= ML.Util.kEpsilon)
{
// if angle is greater than zero
if ((1.0f - cosTheta) > ML.Util.kEpsilon)
{
// use standard slerp
float theta = Mathf.Acos(cosTheta);
float recipSinTheta = 1.0f / Mathf.Sin(theta);
startInterp = Mathf.Sin((1.0f - t) * theta) * recipSinTheta;
endInterp = Mathf.Sin(t * theta) * recipSinTheta;
}
// angle is close to zero
else
{
// use linear interpolation
startInterp = 1.0f - t;
endInterp = t;
}
}
// otherwise, take the shorter route
else
{
// if angle is less than 180 degrees
if ((1.0f + cosTheta) > ML.Util.kEpsilon)
{
// use slerp w/negation of start quaternion
float theta = Mathf.Acos(-cosTheta);
float recipSinTheta = 1.0f / Mathf.Sin(theta);
startInterp = Mathf.Sin((t - 1.0f) * theta) * recipSinTheta;
endInterp = Mathf.Sin(t * theta) * recipSinTheta;
}
// angle is close to 180 degrees
else
{
// use lerp w/negation of start quaternion
startInterp = t - 1.0f;
endInterp = t;
}
}
return(startInterp * start + endInterp * end);
} // End of Slerp()
} // End of IvQuat::Rotate()
//-------------------------------------------------------------------------------
// @ Lerp()
//-------------------------------------------------------------------------------
// Linearly interpolate two quaternions
// This will always take the shorter path between them
//-------------------------------------------------------------------------------
public IvQuat Lerp(ref IvQuat start, ref IvQuat end, float t)
{
// get cos of "angle" between quaternions
float cosTheta = start.Dot(end);
// initialize result
IvQuat result = t * end;
// if "angle" between quaternions is less than 90 degrees
if (cosTheta >= ML.Util.kEpsilon)
{
// use standard interpolation
result += (1.0f - t) * start;
}
else
{
// otherwise, take the shorter path
result += (t - 1.0f) * start;
}
return(result);
} // End of Lerp()
