public static void TwoBoneIk(
Transform bone1Transform, float bone1Length, Transform bone2Transform, float bone2Length,
Vector3 targetPosition, Vector3 elbowTargetPosition, bool getPositiveAngleSolution
)
{
// Get thetas.
var targetOffsetFromBone1 = targetPosition - bone1Transform.position;
var targetDistanceFromBone1 = targetOffsetFromBone1.magnitude;
float theta1InRadians, theta2InRadians;
MathfExtensions.GetTwoBoneIkAngles(
bone1Length, bone2Length, targetDistanceFromBone1, getPositiveAngleSolution,
out theta1InRadians, out theta2InRadians
);
// Rotate bone1 to point to the target, and point the up vector towards the elbow target.
var elbowTargetOffsetFromBone1 = elbowTargetPosition - bone1Transform.position;
var lookAtUpDirection = Vector3Extensions.Reject(elbowTargetOffsetFromBone1, targetOffsetFromBone1);
bone1Transform.LookAt(targetPosition, lookAtUpDirection);
// Apply thetas.
bone1Transform.Rotate(-Vector3.right, Mathf.Rad2Deg * theta1InRadians, Space.Self);
bone2Transform.localRotation = Quaternion.AngleAxis(Mathf.Rad2Deg * theta2InRadians, -Vector3.right);
}