public static void ConstructTransformFromMatrixWithDesiredScale(FMatrix aMatrix, FMatrix bMatrix, FVector desiredScale, ref FTransform outTransform)
{
// the goal of using M is to get the correct orientation
// but for translation, we still need scale
var m = aMatrix * bMatrix;
m.RemoveScaling();
// apply negative scale back to axes
var signedScale = desiredScale.GetSignVector();
m.SetAxis(0, signedScale.X * m.GetScaledAxis(EAxis.X));
m.SetAxis(1, signedScale.Y * m.GetScaledAxis(EAxis.Y));
m.SetAxis(2, signedScale.Z * m.GetScaledAxis(EAxis.Z));
// @note: if you have negative with 0 scale, this will return rotation that is identity
// since matrix loses that axes
var rotation = new FQuat(m);
rotation.Normalize();
// set values back to output
outTransform.Scale3D = desiredScale;
outTransform.Rotation = rotation;
// technically I could calculate this using FTransform but then it does more quat multiplication
// instead of using Scale in matrix multiplication
// it's a question of between RemoveScaling vs using FTransform to move translation
outTransform.Translation = m.GetOrigin();
}
public void RemoveScaling(float tolerance = UnrealMath.SmallNumber)
{
Scale3D = new FVector(1.0f, 1.0f, 1.0f);
Rotation.Normalize();
}