This document describes how to embed
rgl scenes in HTML
HTML document. For more general information about
We assume that the HTML document is produced from R markdown source
rmarkdown. This format mixes
text with Markdown markup with chunks of R code. There is a limited
amount of discussion of other methods.
There are two ways to embed an
rgl scene in the
document. The newest one is recommended: call
setupKnitr with argument
autoprint = TRUE early in the document. This will set
things up to be quite similar to the way standard 2D graphics are
knitr, i.e. it will detect the fact that you’ve
drawn something, and just include it automatically.
autoprint = FALSE is used or no call is made to
setupKnitr(), an explicit call to
rglwidget will produce a “widget”
which can be embedded into your document by printing it. This document
uses that method.
Older methods (e.g.
writeWebGL or various hooks) that
were used before
rgl version 0.102.0 are no longer
Most browsers now support WebGL, but in some browsers it may be disabled by default. See https://get.webgl.org for help on a number of different browsers.
We start with a simple plot of the iris data. We insert a code chunk
and call the
with optional argument
elementId. This allows later
the plot, so that they can be manipulated later. (The first example in
Controls uses tags instead of saving the
Next we insert a button to toggle the display of the data.
sceneId is the same as the
ids are the object
ids of the objects that we’d like to toggle, and the
is the label shown on the button. To find the names in the
plotids variable, apply
##  "data" "axes" "xlab" "ylab" "zlab"
## data axes xlab ylab zlab ## 13 14 15 16 17
magrittror base pipes
It can be error-prone to set the
elementId in the
rglwidget() to match the
sceneId in the
below). In the usual case where both are intended to appear together,
pipes can be used quite flexibly: the first argument of the control
widget accepts the result of
rglwidget() (or other control
widgets), and the
controllers argument of
rglwidget() accepts control widgets. In R 4.1.0, the new
base pipe operator
|> should be usable in the same
If you have R 4.1.0 or greater, this should do the same:
You can swap the order of button and scene; use the
magrittr dot (or the
=> syntax in base
pipes) to pass the
Control before widget example.
or using R 4.1.0 or later,
We have seen how to change the contents of the plot using
We can do more elaborate displays. For example, we can redo the previous
plot, but with the three species as separate “spheres” objects and
buttons to toggle them:
clear3d() # Remove the earlier display with(subset(iris, Species == "setosa"), spheres3d(Sepal.Length, Sepal.Width, Petal.Length, col=as.numeric(Species), radius = 0.211, tag = "setosa")) with(subset(iris, Species == "versicolor"), spheres3d(Sepal.Length, Sepal.Width, Petal.Length, col=as.numeric(Species), radius = 0.211, tag = "versicolor")) with(subset(iris, Species == "virginica"), spheres3d(Sepal.Length, Sepal.Width, Petal.Length, col=as.numeric(Species), radius = 0.211, tag = "virginica")) aspect3d(1,1,1) decorate3d(tag = "axes") rglwidget() %>% toggleWidget(tags = "setosa") %>% toggleWidget(tags = "versicolor") %>% toggleWidget(tags = "virginica") %>% toggleWidget(tags = "axes") %>% asRow(last = 4)
Toggle subsets example.
Since we skipped the
label argument, the buttons are
labelled with the values of the tags. The
asRow function is
toggleWidget() is actually a convenient wrapper for two
playwidget() adds the button to the web page (and can also
add sliders, do animations, etc.), while
chooses a subset of objects to display.
For a more general example, we could use a slider to select several subsets of the data in the iris display. For example,
There are several other “control” functions.
For example, the following code (similar to the
play3d example) rotates the scene in
a complex way.
increments, so that motion appears smooth. However, storing 300
userMatrix values would take up a lot of space, so we use
only do linear interpolation, not the more complex spline-based SO(3)
interpolation done by
par3dinterp. Because of this, we
need to output 15 steps from
that the distortions of linear interpolation are not visible.
is a more general function to set the value of properties of the scene.
Currently most properties are supported, but use does require knowledge
of the internal implementation.
allows the user to control the location of a clipping plane by moving a
Less general than
This function sets attributes of individual vertices in a scene. For
example, to set the x-coordinate of the closest point in the setosa
group, and modify its colour from black to white,
setosavals <- subset(iris, Species == "setosa") which <- which.min(setosavals$Sepal.Width) init <- setosavals$Sepal.Length[which] rglwidget() %>% playwidget( vertexControl(values = matrix(c(init, 0, 0, 0, 8, 1, 1, 1), nrow = 2, byrow = TRUE), attributes = c("x", "red", "green", "blue"), vertices = which, tag = "setosa"), step = 0.01)
A related function is
though it uses a very different specification of the attributes. It is
used when the slider controls the “age” of the scene, and attributes of
vertices change with their age.
To illustrate we will show a point moving along a curve. We give two
ageControl calls in a list; the first one controls the
colour of the trail, the second controls the position of the point:
time <- 0:500 xyz <- cbind(cos(time/20), sin(time/10), time) lineid <- plot3d(xyz, type="l", col = "black")["data"] sphereid <- spheres3d(xyz[1, , drop=FALSE], radius = 8, col = "red") rglwidget() %>% playwidget(list( ageControl(births = time, ages = c(0, 0, 50), colors = c("gray", "red", "gray"), objids = lineid), ageControl(births = 0, ages = time, vertices = xyz, objids = sphereid)), start = 0, stop = max(time) + 20, rate = 50, components = c("Reverse", "Play", "Slower", "Faster", "Reset", "Slider", "Label"), loop = TRUE)
While not exactly a control in the sense of the other functions in
this section, the
function is used to add an HTML control to a display to allow the user
to select the mouse mode.
For example, the display below initially allows selection of particular points, but the mouse mode may be changed to let the user rotate the display for a another view of the scene.
rglShared() call used here is described
rgl displays will contain several elements: one or
rgl scenes and controls. Internally
combineWidgets function from the
rgl package provides 3 convenience functions for
arranging displays. We have already met the first: the
%>%. When the display is
constructed as a single object using pipes, the objects in the pipeline
will be arranged in a single column.
The second convenience function is
This takes as input a list of objects or a
object (perhaps the result of a pipe), and rearranges (some of) them
into a horizontal row. As in the toggleWidget
last argument can be used to limit the
asRow to the specified number of components. (If
last = 0, all objects are stacked: this can be useful if
some of them are not from the
rgl package, so piping
doesn’t work for them.)
can be used to extract the HTML element ID from an HTML widget. This is
useful when combining widgets that are not all elements of the same
pipe, as in the
crosstalk example below.
If these convenience functions are not sufficient, you can call
or other functions from
manipulateWidget for more
flexibility in the display arrangements.
package allows widgets to communicate with each other. Currently it
supports selection and filtering of observations.
rgl can send, receive and display these messages. An
rgl display may have several subscenes, each displaying
different datasets. Each object in the scene is potentially a shared
dataset in the
The linking depends on the
rgl id value for an object in the current scene,
creates a shared data object containing the coordinates of the vertices
rgl object. This object is passed to
rglwidget in the
shared argument. It can also be passed to other widgets
that accept shared data, linking the two displays.
If a shared data object has been created in some other way, it can be
linked to a particular
id value by copying
group properties as shown in the
# This example requires the crosstalk package. # We skip it if crosstalk is not available. library(crosstalk) sd <- SharedData$new(mtcars) ids <- plot3d(sd$origData(), col = mtcars$cyl, type = "s") # Copy the key and group from existing shared data rglsd <- rglShared(ids["data"], key = sd$key(), group = sd$groupName()) rglwidget(shared = rglsd) %>% asRow("Mouse mode: ", rglMouse(getWidgetId(.)), "Subset: ", filter_checkbox("cylinderselector", "Cylinders", sd, ~ cyl, inline = TRUE), last = 4, colsize = c(1,2,1,2), height = 60)
If multiple objects in the
rgl scene need to be
considered as shared data, you can pass the results of several
rglShared() calls in a list,
rglwidget(shared = <list>). The key values will
be assumed to be shared across datasets; if this is not wanted, use a
prefix or some other means to make sure they differ between objects.
If the same
rgl id is used in more than one
rglShared() object, it will respond to messages from all of
them. This may lead to undesirable behaviour as one message cancels the
We repeat the initial plot from this document:
We might like a button on the web page to cause a change to the display, e.g. a rotation of the plot. First we add buttons, with the “onclick” event set to a function described below:
<button type="button" onclick="rotate(10)">Forward</button> <button type="button" onclick="rotate(-10)">Backward</button>
which produces these buttons:
We stored the subscene number that is currently active in
subid in the code chunk above, and use it as
in the script below.
knitr substitutes the value when it processes the
document.getElementById to retrieve the
<div> component of the web page containing the scene.
It will have a component named
rglinstance which contains
information about the scene that we can modify:
If we had used
webGL=TRUE in the chunk header, the
knitr WebGL support would create a global object with a
name of the form
<chunkname>rgl. For example, if the
code chunk was named
plot3d2, the object would be called
plot3d2rgl, and this code would work: