How to estimate new quaternion when x axis becomes -x ?
In short, I need to estimate the new quaternion when rotation around y becomes 180-y.
if angle around y is 30 degrees, around x=20 degrees, and around z is z = 70 degrees then around y should become 180-30 degrees because x becomes -x
In Quaternions: The new y in -x should be (180-30)*pi/180 and its quaternions are found as follows (original in https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles but for different coordinate system)
a = 180-30; //180-30;
ax = 20 * Math.PI/180;
ay = a * Math.PI/180;
az = 70 * Math.PI/180;
t0 = Math.cos(ay * 0.5); // yaw
t1 = Math.sin(ay * 0.5);
t2 = Math.cos(az * 0.5); // roll
t3 = Math.sin(az * 0.5);
t4 = Math.cos(ax * 0.5); // pitch
t5 = Math.sin(ax * 0.5);
t024 = t0 * t2 * t4;
t025 = t0 * t2 * t5;
t034 = t0 * t3 * t4;
t035 = t0 * t3 * t5;
t124 = t1 * t2 * t4;
t125 = t1 * t2 * t5;
t134 = t1 * t3 * t4;
t135 = t1 * t3 * t5;
x = t025 + t134;
y =-t035 + t124;
z = t034 + t125;
w = t024 - t135;