// Given a matrix, decompose that matrix into a Keyframe.
// This works for matrices that don't contain shear or off-axis scale.
public static Keyframe CreateFromMatrix(ref Matrix mat)
{
Keyframe k = new Keyframe();
return(CreateFromMatrix(ref mat, k));
}
/// <summary>
/// Given a base keyframe, and a "delta" keyframe, construct a keyframe that
/// represents the first transformation followed by a weighted amount of the
/// second keyframe.
/// </summary>
/// <param name="first">The base keyframe. Cannot be the same object as "result."</param>
/// <param name="second">The delta keyframe. Can be the same object as "result."</param>
/// <param name="weight">How much of the delta keyframe to apply (typically 0 .. 1)</param>
/// <param name="result">The composed keyframe data will be stored here.</param>
/// <returns>result (for convenience)</returns>
public static Keyframe Compose(Keyframe first, Keyframe second, float weight, Keyframe result)
{
#if DEBUG
// "first" and "result" can't be the same objects, although
// "second" and "result" can be.
System.Diagnostics.Debug.Assert(first != result);
if (first == null)
{
throw new ArgumentNullException("left");
}
if (second == null)
{
throw new ArgumentNullException("right");
}
if (result == null)
{
throw new ArgumentNullException("result");
}
#endif
#if !MATRIXFRAMES
Interpolate(Identity, second, weight, result);
Vector3 pos;
Vector3.Transform(ref result.pos_, ref first.ori_, out pos);
result.pos_ = first.pos_ + pos;
result.scale_ = first.scale_ * second.scale_;
// Yes, XNA does quaternions in a different order from matrices. Blech.
result.ori_ = second.ori_ * first.ori_;
#else
result.transform_ = first.transform_ * (Matrix.Identity * (1 - weight) + second.transform_ * weight);
#endif
return(result);
}