Animations
With Makie it is easy to create animated plots. Animations work by making changes to data or plot attribute Observables and recording the changing figure frame by frame. You can find out more about the Observables workflow on the Observables & Interaction page.
A simple example
To create an animation you need to use the
record
function.
First you create a
Figure
. Next, you pass a function that modifies this figure frame-by-frame to
record
. Any changes you make to the figure or its plots will appear in the final animation. You also need to pass an iterable which has as many elements as you want frames in your animation. The function that you pass as the first argument is called with each element from this iterator over the course of the animation.
As a start, here is how you can change the color of a line plot:
using GLMakie
using Makie.Colors
fig, ax, lineplot = lines(0..10, sin; linewidth=10)
# animation settings
nframes = 30
framerate = 30
hue_iterator = range(0, 360, length=nframes)
record(fig, "color_animation.mp4", hue_iterator;
framerate = framerate) do hue
lineplot.color = HSV(hue, 1, 0.75)
end
Passing a function as the first argument is usually done with Julia's
do
-notation, which you might not be familiar with. Instead of the above, we could also have written:
function change_function(hue)
lineplot.color = HSV(hue, 1, 0.75)
end
record(change_function, fig, "color_animation.mp4", hue_iterator; framerate = framerate)
File formats
Video files are created with
FFMPEG.jl
. You can choose from the following file formats:
-
.mkv
(the default, doesn't need to convert) -
.mp4
(good for web, widely supported) -
.webm
(smallest file size) -
.gif
(lowest quality with largest file size)
Animations using
Observables
Often, you want to animate a complex plot over time, and all the data that is displayed should be determined by the current time stamp. Such a dependency is really easy to express with
Observables
or
Nodes
.
We can save a lot of work if we create our data depending on a single time
Node
, so we don't have to change every plot's data manually as the animation progresses.
Here is an example that plots two different functions. The y-values of each depend on time and therefore we only have to change the time for both plots to change. We use the convenient
@lift
macro which denotes that the
lift
ed expression depends on each Observable marked with a
$
sign.
time = Node(0.0)
xs = range(0, 7, length=40)
ys_1 = @lift(sin.(xs .- $time))
ys_2 = @lift(cos.(xs .- $time) .+ 3)
fig = lines(xs, ys_1, color = :blue, linewidth = 4,
axis = (title = @lift("t = $(round($time, digits = 1))"),))
scatter!(xs, ys_2, color = :red, markersize = 15)
framerate = 30
timestamps = range(0, 2, step=1/framerate)
record(fig, "time_animation.mp4", timestamps;
framerate = framerate) do t
time[] = t
end
You can set most plot attributes equal to
Observable
s, so that you need only update a single variable (like time) during your animation loop.
For example, to make a line with color dependent on time, you could write:
time = Node(0.0)
color_observable = @lift(RGBf($time, 0, 0))
fig = lines(0..10, sin, color = color_observable)
record(fig, "color_animation_2.mp4", timestamps; framerate = framerate) do t
time[] = t
end
Appending data with Observables
You can also append data to a plot during an animation. Instead of passing
x
and
y
(or
z
) values separately, it is better to make a
Node
with a vector of
Point
s, so that the number of
x
and
y
values can not go out of sync.
points = Node(Point2f[(0, 0)])
fig, ax = scatter(points)
limits!(ax, 0, 30, 0, 30)
frames = 1:30
record(fig, "append_animation.mp4", frames;
framerate = 30) do frame
new_point = Point2f(frame, frame)
points[] = push!(points[], new_point)
end
Animating a plot "live"
You can animate a live plot easily using a loop. Update all
Observables
that you need and then add a short sleep interval so that the display can refresh:
points = Node(Point2f[randn(2)])
fig, ax = scatter(points)
limits!(ax, -4, 4, -4, 4)
fps = 60
nframes = 120
for i = 1:nframes
new_point = Point2f(randn(2))
points[] = push!(points[], new_point)
sleep(1/fps) # refreshes the display!
end
These docs were autogenerated using Makie: v0.15.3, GLMakie: v0.4.7, CairoMakie: v0.6.6, WGLMakie: v0.4.7