This document describes how to embed
rgl, see rgl Overview.
We assume that the HTML document is produced from R markdown source using
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 recommended one is to call
rglwidget to produce a “widget” which can be embedded into your document by printing it.
The older method is described in the Legacy WebGL Methods document. It is likely to be supported for some time, but is not recommended for new projects, as the widget method is easier for me to maintain.
I have conducted experiments on a third method. This is intended to be similar to the way standard 2D graphics are included by
knitr, i.e. it will detect the fact that you’ve drawn something, and just include it automatically. At present it is not recommended, but that may change in the future.
Most browsers now support WebGL, but in some browsers it may be disabled by default. See http://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
rglwidget function with optional argument
Next we insert a button to toggle the display of the data.
sceneId is the same as the
elementId we used in
ids are the object ids of the objects that we’d like to toggle, and the
label 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 ## 7 8 9 10 11
It can be error-prone to set the
elementId in the
rglwidget() to match the
sceneId in the
playwidget(), described below). In the usual case where both are intended to appear together,
magrittr-style 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. For example,
You can swap the order of button and scene; use the
magrittr dot to pass the
rglwidget in the
We have seen how to change the contents of the plot using
toggleWidget. 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 setosa <- with(subset(iris, Species == "setosa"), spheres3d(Sepal.Length, Sepal.Width, Petal.Length, col=as.numeric(Species), radius = 0.211)) versicolor <- with(subset(iris, Species == "versicolor"), spheres3d(Sepal.Length, Sepal.Width, Petal.Length, col=as.numeric(Species), radius = 0.211)) virginica <- with(subset(iris, Species == "virginica"), spheres3d(Sepal.Length, Sepal.Width, Petal.Length, col=as.numeric(Species), radius = 0.211)) aspect3d(1,1,1) axesid <- decorate3d() rglwidget() %>% toggleWidget(ids = setosa) %>% toggleWidget(ids = versicolor) %>% toggleWidget(ids = virginica) %>% toggleWidget(ids = axesid) %>% asRow(last = 4)
Since we skipped the
label argument, the buttons are labelled with the name of the variable passed as
asRow function is discussed below.
toggleWidget() is actually a convenient wrapper for two functions:
playwidget() adds the button to the web page (and can also add sliders, do animations, etc.), while
subsetControl() 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.
par3dinterp. Because of this, we need to output 15 steps from
par3dinterpControl so that the distortions of linear interpolation are not visible.
propertyControl 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.
clipplaneControl allows the user to control the location of a clipping plane by moving a slider.
Less general than
vertexControl. 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, objid = setosa), step = 0.01)
A related function is
ageControl, 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
rglMouse 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.