Film computations
Pkg.add("Reel")You will need ffmpeg and imagemagick installed to use Reel. This package supersedes ComposeVideo.jl
Reel exports the all-important function roll which you can use to roll the camera on various arguments:
using Reel
using Gadfly
function render(t, dt)
# t is the time into the sequence
# dt is the time to advance for the next frame
# any expression that results in an object which can be
# rendered as png or jpg
plot([x -> sin(x+t*π), x -> cos(x+t*π)], 0, 6)
end
film = roll(render, fps=30, duration=2)
write("output.gif", film) # Write to a gif file
# Or
write("file.webm", film) # Write to a webm video
# Or
write("file.mp4", film) # An mp4 formatted video
The same thing can be concisely written with Julia's do syntax:
film = roll(fps=30, duration=2) do t, dt
plot([x -> sin(x+t*π), x -> cos(x+t*π)], 0, 6)
end
write("output.gif", film)Note that the fps you specify to roll will be enforced no matter how long the computation actually takes: you set the speed at which you want to watch it.
Reel can also render an abstract array of objects:
using Compose
Compose.set_default_graphic_size(3inch, 3inch) # Square
# draw a regular n-gon
ngon(n) = compose(context(units=UnitBox(-1, -1, 2, 2)), fill("lightblue"),
polygon([(cos(x), sin(x)) for x in π/2:2π/n:3.5π]))
roll(map(ngon, vcat([3:10], [9:-1:3])), fps=5)
Reel exports Frames, a type for a collection of frames.
Frames constructor takes a MIME type of the frames, and the fps at which the animation should be rendered. e.g.
You can push a new frames to a Frames object using push!.
# A Glider gun from Conway's game of Life
using Reel
frames = Frames(MIME("image/png"), fps=2)
g = glider_gun # initial board state
for i=1:31
push!(frames, draw(g))
g = decidefate(g)
end
frames
You can render a Frames object as usual:
write("output.webm", frames)A call to roll returns a Frames object. A method writemime(::IO, ::MIME{symbol("text/html"),::Frames) orchestrates the rendering of a Frames object in IJulia. Any cell which results in a Frames results in the animation being rendered. By default, a webm video is generated. You can change this behavior:
Reel.set_output_type("gif") # or "mp4"# particles in a box.
using Color, Compose
box(x) = let i = floor(x)
i%2==0 ? x-i : 1+i-x
end
colors = distinguishable_colors(10, lchoices=[82.])
dots(points) = [(context(p[1], p[2], .03, .03), fill(colors[i%10+1]), circle())
for (i, p) in enumerate(points)]
velocities = [(rand(), rand()) for i in 1:40]
roll(fps=30, duration=10.0) do t, dt
compose(context(),
dots([map(v -> box(v*t + 0.5), (vx, vy)) for (vx, vy) in velocities])...)
end
# Solution of Helmholtz equation with Dirichlet BC using ApproxFun
using ApproxFun
B=dirichlet(d)
Δ=lap(d)
plots = [ApproxFun.contour(pdesolve([B,Δ+k*I],ones(4),150))
for k=vcat([1:1.0:100], [99:-1.0:1])]
roll(plots, fps=24)
# Warning: this gif is 8 mb!
Fin.
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