Visualization of first documentation example about topopt.jl

[yijiangh]

Good catch! By default, we need the user to pass in the deformation vector u and then the deformation exaggeration slider is actually doing something. I think we will try to keep this assumption to make the API simple, but you are right that an ineffective slider is misleading and we should hide this slider if no u is passed in.

And until recently, Makie did not assume GLMakie as its default and required the users to specify the backend explicitly. We should update the documentation and the @require stuff in the visualization module.

I will push a PR on the visualizer soon.

For now, if you want to visualize the optimized design's deformation under load, you can do the following:

solver.vars = result.minimizer
solver()

visualize(problem, solver.u, topology=result.minimizer)