Detect where the enemy is facing using Vector3.Agnle or Dot only "Y" axis rotation?

I make AI system and I wanna know where enemy is facing depending on me. And I use Vector3.Angle. It works well, but I wanna check this value only with "Y" axis rotation. But this line of code works with "X" and "Z" axis rotations too. How can I disable "X" and "Z" axis rotation? Just I wanna get "Y" axis rotation value.

Code (CSharp):

1. float angle = Vector3.Angle(enemy.transform.forward, transform.forward);

 

I'm not 100% positive this is what you want, but one way is to "flatten" the vectors before you use them.

Code (csharp):

1. // copy original vectors out
2. Vector3 enemyForward = enemy.transform.forward;
3. Vector3 myForward = transform.forward;
4.  
5. // flatten in Y since we want angle around Y:
6. enemyForward.y = 0;
7. myForward.y = 0;
8.  
9. // now do your angle computation above:
10. float angle = Vector3.Angle( enemyForward, myForward);

Is that what you are trying to do? It makes the two vectors exist only in the flat plane X/Z.

 

Still, it is not like how I want. I posted a video to show a problem. Y rotates well, but X axis still change the value of the angle. I want to disable X and Z axes calculation. Z is disabled, but X axis still change the value of the angle. This code is good for flat plane, but for terrain or other surface it is not good, because of the X axis calculation. Is there any way to solve this problem? Also I used Dot, but still no hope.

Code (CSharp):

1. // It did not work. Stil X axis change the value of angle
2. enemyForward.y = 0;
3. myForward.y = 0;
4.  

Video starts at 0:14

 

If anyone knows how to solve this issue, please help me.