Conversion 4x4 matrix to quaternion cginc

MatrixToQuaternion.cginc

#ifndef _MATRIX_TO_QUATERNION_
#define _MATRIX_TO_QUATERNION_

// http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/
float4 matrix_to_quaternion(float4x4 m) {

	float tr = m[0][0] + m[1][1] + m[2][2];
	float4 q = float4(0, 0, 0, 0);

	if (tr > 0) {
		float s = sqrt(tr + 1.0) * 2; // S=4*qw 
		q.w = 0.25 * s;
		q.x = (m[2][1] - m[1][2]) / s;
		q.y = (m[0][2] - m[2][0]) / s;
		q.z = (m[1][0] - m[0][1]) / s;
	} else if ((m[0][0] > m[1][1]) && (m[0][0] > m[2][2])) {
		float s = sqrt(1.0 + m[0][0] - m[1][1] - m[2][2]) * 2; // S=4*qx 
		q.w = (m[2][1] - m[1][2]) / s;
		q.x = 0.25 * s;
		q.y = (m[0][1] + m[1][0]) / s;
		q.z = (m[0][2] + m[2][0]) / s;
	} else if (m[1][1] > m[2][2]) {
		float s = sqrt(1.0 + m[1][1] - m[0][0] - m[2][2]) * 2; // S=4*qy
		q.w = (m[0][2] - m[2][0]) / s;
		q.x = (m[0][1] + m[1][0]) / s;
		q.y = 0.25 * s;
		q.z = (m[1][2] + m[2][1]) / s;
	} else {
		float s = sqrt(1.0 + m[2][2] - m[0][0] - m[1][1]) * 2; // S=4*qz
		q.w = (m[1][0] - m[0][1]) / s;
		q.x = (m[0][2] + m[2][0]) / s;
		q.y = (m[1][2] + m[2][1]) / s;
		q.z = 0.25 * s;
	}

	return q;
}

#endif