possible issue in "spActiveZebrafishVicsek()"

[YUXUANCHENG]

cells/src/active2D.cpp

Line 2237 in deeef56

psi.at(ci) += dt*((1.0/vtau)*asin(cos(psi.at(ci))*cell(ci).cvel(1) - sin(psi.at(ci))*cell(ci).cvel(0)) + 4.0*Dr*PI*(r1 - 0.5));

file location: /src/active2D.cpp
function: spActiveZebrafishVicsek
possible issue: "asin(cos(psi.at(ci))*cell(ci).cvel(1) - sin(psi.at(ci))*cell(ci).cvel(0))" where cvel needs to be normalized. Because: | a x b | = |a| . |b| . sin(theta) then sin(theta) = | a x b | / (|a| . |b|).

But be careful that (|a| . |b|) could be zero, thus should divide by (|a| . |b| + e) where e is a small number.

[jacktreado]

Good point! I'll add this to my next commit!

Also I'm very excited, this is the first comment I've ever gotten on my github haha