Quaternion.LookRotation with just euler angles

Hello community,

am converting a swarming\flocking algorithm to highly optimized burst-code. Optimization is important here since it's performed on thousands of particles.

What I'm struggling with is, optimizing this code where pr is a particle struct (not using jobs right away before I haven't converted the code to use the Mathematics library since this makes debugging easier):

Code (CSharp):

1. Quaternion rotationCur = Quaternion.LookRotation(towardsVec);
2. pr.rotation3D = rotationCur.eulerAngles;

It seems highly inefficient to use Quaternions here only to convert back to eulers.

Especially since when using "quaternion" from Mathematics (which is highly recommended when using the burst compiler, right?), I am forced to compute the euler angles in code, since there is no implementation in the library (there's a whole thread where the devs argue that's not something needed q_q).

Does someone know how to compute what LookRotation(vec, up) does, directly into euler angles?

Also on a sidenote,
why is this despite Quat->quat conversion:

Code (CSharp):

1. quaternion rotationCur = Quaternion.LookRotation(towardsVec);

WAY faster than this quat-only solution (at least without burst compilation about 3 times faster)?

Code (CSharp):

1. quaternion rotationCur = quaternion.LookRotation(towardsVec, math.up());

Huge thanks in advance!

 

There was a DOTS flocking demo some years back, I remember seeing it in a GDC video.

See if you can perhaps find the code for that and see what they did to get the boids pointed properly.