根据矩阵计算角度

gvr_vec3f rotationMatrixToEulerAngles(gvr_mat4f &R)
{

    float sy = (float) sqrt(R.m[0][0] * R.m[0][0] + R.m[1][0] * R.m[1][0] );

    bool singular = sy < 1e-6; // If

    float x, y, z;
    if (!singular)
    {
        x = (float) atan2(R.m[2][1] , R.m[2][2]);
        y = (float) atan2(-R.m[2][0], sy);
        z = (float) atan2(R.m[1][0], R.m[0][0]);
    }
    else
    {
        x = (float) atan2(-R.m[1][2], R.m[1][1]);
        y = (float) atan2(-R.m[2][0], sy);
        z = 0;
    }
    gvr_vec3f i;
    i.x = (float) (x * (180.0f / M_PI));
    i.y = (float) (y * (180.0f / M_PI));
    i.z = (float) (z * (180.0f / M_PI));
    return i;
}