Question about quaterions rotation

Hi, I`m having a problem with understanding how quaternion rotation works. I have turret and projectile, that i want to shoot from it. The turret can rotate in any direction.

Projectile:


Turret:


I have my FixedRateSpawnerSystem for creating projectiles:

Code (CSharp):

1. Entities
2.         .ForEach((in ProjectileSpawnerComponent spawner, in LocalToWorld localToWorld, in Rotation localRotation) =>
3.         {
4.             var projectileEntity = ecb.Instantiate(spawner.Prefab);
5.  
6.             var spawnPos = localToWorld.Position;
7.             var rotation = localToWorld.Rotation;
8.  
9.             var halfPi =  Unity.Mathematics.math.PI / 2;
10.             var rotationQuaterion = quaternion.RotateZ(halfPi);
11.             var normalizedRotation = math.normalize(rotation);
12.             var newRotation = math.mul(normalizedRotation, rotationQuaterion);
13.  
14.             // var lookRotationSafe = quaternion.LookRotationSafe(localToWorld.Forward, localToWorld.Right);
15.  
16.             ecb.SetComponent(projectileEntity, new Translation { Value = spawnPos });
17.             ecb.SetComponent(projectileEntity, new Rotation { Value = newRotation });
18.             ecb.SetComponent(projectileEntity, new ProjectileComponent
19.             {
20.                 SpawnTime = spawnTime,
21.                 SpawnPos = spawnPos,
22.             });
23.         })

But this rotation, creates weird bugs, on 90 and -90 degrees:


I can fix that just by using quaternion.LookRotationSafe:

Code (CSharp):

1. Entities
2.         .ForEach((in ProjectileSpawnerComponent spawner, in LocalToWorld localToWorld, in Rotation localRotation) =>
3.         {
4.             var projectileEntity = ecb.Instantiate(spawner.Prefab);
5.  
6.             var spawnPos = localToWorld.Position;
7.             var rotation = localToWorld.Rotation;
8.  
9.             //var halfPi =  Unity.Mathematics.math.PI / 2;
10.             //var rotationQuaterion = quaternion.RotateZ(halfPi);
11.             //var normalizedRotation = math.normalize(rotation);
12.             //var newRotation = math.mul(normalizedRotation, rotationQuaterion);
13.  
14.              var lookRotationSafe = quaternion.LookRotationSafe(localToWorld.Forward, localToWorld.Right);
15.  
16.             ecb.SetComponent(projectileEntity, new Translation { Value = spawnPos });
17.             ecb.SetComponent(projectileEntity, new Rotation { Value = lookRotationSafe });
18.             ecb.SetComponent(projectileEntity, new ProjectileComponent
19.             {
20.                 SpawnTime = spawnTime,
21.                 SpawnPos = spawnPos,
22.             });
23.         })

That's, produces, result I wanted:


My question is what I`m missing or do not understand, about the first method?

 

It's hard to tell but I think you should not normalize old rotation.