% Restore a big raytrace (e.g. from raytrace_longrun) and plot the density. Resave the file with
% this new density information.
function density_longrun(filename)

t0 = cputime;

load(filename);
t1 = cputime;
cpu_time_to_load_file = t1 - t0

ray_density = density(xs,ys,L,0.01);

t2 = cputime;
cpu_time_to_calculate_density = t2 - t1

clear t0  %Don't want this saved!
save("-binary",filename);

t3 = cputime;
cpu_time_to_save = t3 - t2