Funky and backward diagrams in TeX Live 2019/2020.

[diaza]

Apologies if this is not the right area for this issue.

I'm using TikZ-Feynman for a document I'm writing on Overleaf, and when I would copy example code for some diagrams they would end up looking funky. For example, the following code
\feynmandiagram [large, vertical=e to f] { a -- [fermion] b -- [photon, momentum=\(k\)] c -- [fermion] d, b -- [fermion, momentum'=\(p_{1}\)] e -- [fermion, momentum'=\(p_{2}\)] c, e -- [gluon] f, h -- [fermion] f -- [fermion] i; };
should produce this:

but my document was outputting the following

.

In addition to the funkiness in the middle, the arrows are pointing in opposite directions, which I was noticing in all the Feynman diagrams I was drawing.

I found that this issue was resolved when I changed the TeX Live version from 2020/2019 to 2018.

I don't know if this is a bug with TikZ-Feynman, with the TeX Live distributions, or with Overleaf.

[diaza]

Another, simpler example:
When I draw
\feynmandiagram [vertical=a to b] { i1 [particle=\(\nu_{\beta}\)] -- [fermion] a -- [fermion] f1 [particle=\(\beta\)], a -- [boson] b, };

I get the following with TeX Live 2019 & 2020:

And the following with TeX Live 2018:

The TeX Live 2018 drawing is my expectation.

[Scientificaa]

Hi, has it been solved now? I'm also facing this problem, and it seems that I cant find any solution

[JP-Ellis]

Unfortunately, I do not know the exact reason behind this. I suspect it is due to a different source of randomness and you might have to set the random seed manually to get it to work.

[turner-julian]

I also have run into the same issue trying to run the code used in the documentation of tikz-feynman:

Has there been any progress made with this specific issue?

[JP-Ellis]

I will be releasing a new version of TikZ-Feynman in the next few weeks, and hope to used a fixed seed to help ensure reproducibility across the different runtime environments; however, the underlying algorithm is stochastic and I don't know in enough details whether the underlying pseudo-random number generator in Lua is deterministic across different environments.

In any case, if you do get the 'wrong' layout, you can tweak the momentum to momentum' to switch the lines; or fermion to anti fermion for arrows. You can also specify a specific seed if need be.