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September 7, 2017 00:18
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% vector field | |
dxdt = @(x) [x(2);-x(1)]; | |
% mesh | |
[GX,GY] = meshgrid(linspace(-2*pi,2*pi,100),linspace(-10,10,100)); | |
% stream | |
DX = arrayfun(@(x,y) [1,0]*dxdt([x;y]),GX,GY); | |
DY = arrayfun(@(x,y) [0,1]*dxdt([x;y]),GX,GY); | |
[verts,averts] = streamslice(GX,GY,DX,DY,400); | |
iverts = interpstreamspeed(GX,GY,DX,DY,verts,1/60/3); | |
% visualize | |
v = VideoWriter('stream.m4v','MPEG-4'); | |
v.FrameRate=60; | |
open(v) | |
nframe = 60*10-1; | |
seglen = 60; | |
offset =randi(seglen,numel(iverts),1)-1; | |
frames = cell(seglen,1); | |
for frame=1:seglen | |
fig = figure(6); | |
clf | |
fig.Position = [fig.Position(1:2),1024,768]; | |
axes('Units', 'normalized', 'Position', [0 0 1 1]) | |
set(fig,'Color',[0,0,0.2]) | |
colormap([linspace(0,0,100);linspace(0,1,100);linspace(0.2,1,100)]') | |
hold on | |
for k=1:length(iverts) | |
xy = iverts{k}; | |
C = mod((0:(size(xy,1)-1))-frame+offset(k),seglen)/(seglen-1); | |
C = exp(-(1-C)*1); | |
xy(end+1,:)=[0,NaN]; | |
patch(xy(:,1)',xy(:,2)',[C,0],'EdgeColor','interp','LineWidth',0.5) | |
end | |
xlim([min(GX(:)),max(GX(:))]) | |
ylim([min(GY(:)),max(GY(:))]) | |
set(gca,'Color',[0,0,0.2]) | |
drawnow | |
frames{frame}=getframe(gcf); | |
end | |
for frame=1:nframe | |
writeVideo(v,frames{mod(frame,seglen)+1}) | |
end | |
close(v) |
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