How to assign the direction and material properties of of each fiber with Gibbon?

[gibboncode]

How to assign the direction and material properties of of each fiber with Gibbon?

[danielcpnkimo]

Yes, I've tried and it works. Sorry for my delayed reply.

[Kevin-Mattheus-Moerman]

The following new demos (those with _febio are new and _FEBio are old demos) map fiber directions:
DEMO_febio_0015_cube_fibers_transiso
DEMO_febio_0024_active_contraction_tongue

The former is a cube where all fibers have the same direction (but it still uses an array of fiber directions which could be spatially varying in direction) and the latter is a tongue model where each element has its own fiber direction. As you can see from these demos you create an ElementData entry in the MeshData section where you define the mat_axis for each element. I find this to be the most convenient way to specify the fiber directions

%MeshData section
% -> ElementData
febio_spec.MeshData.ElementData{1}.ATTR.elem_set=febio_spec.Geometry.ElementSet{1}.ATTR.name;
febio_spec.MeshData.ElementData{1}.ATTR.var='mat_axis';

for q=1:1:size(E,1)
    febio_spec.MeshData.ElementData{1}.elem{q}.ATTR.lid=q;
    febio_spec.MeshData.ElementData{1}.elem{q}.a=a(q,:);
    febio_spec.MeshData.ElementData{1}.elem{q}.d=d(q,:);
end

I generally define the fiber direction to be the 3rd direction so in this case it would be along cross(a,d).

Does this make sense/answer your question?