# rgl Overview

source("setup.R") knitr::opts_chunk$set(rgl.newwindow = TRUE) set.seed(123) ## Introduction The rgl package is used to produce interactive 3-D plots. It contains high-level graphics commands modelled loosely after classic R graphics, but working in three dimensions. It also contains low level structure inspired by (but incompatible with) the grid package. This document gives an overview. See the help pages for details. ### About this document This document was written in R Markdown, using the knitr package for production. It corresponds to rgl version r packageVersion("rgl"). Most of the highlighted function names are HTML links. The internal links should work in any browser; the links to help topics should work if you view the vignette from within the R help system. The document includes WebGL figures. To view these, you must have Javascript and WebGL enabled in your browser. Some older browsers may not support this -- see http://get.webgl.org for tests and links to a discussion. ## Basics and High Level Functions The r indexfns("plot3d") function plots points within an rgl window. It is similar to the classic r linkfn("plot", pkg="graphics") function, but works in 3 dimensions. For example with(iris, plot3d(Sepal.Length, Sepal.Width, Petal.Length, type="s", col=as.numeric(Species))) rglwidget() can be used to plot three columns of the iris data. Allowed plot types include "p", "l", "h", "s", meaning points, lines, segments from z=0, and spheres. There's a lot of flexibility in specifying the coordinates; the r linkfn("xyz.coords", pkg = "grDevices") function from the grDevices package is used for this. You can use your mouse to manipulate the plot. The default is that if you click and hold with the left mouse button, you can rotate the plot by dragging it. The right mouse button is used to resize it, and the middle button changes the perspective in the point of view. If you call r linkfn("plot3d") again, it will overwrite the current plot. To open a new graphics window, use r linkfn("open3d"). The other high level function is r indexfns("persp3d") to draw surfaces. It is similar to the classic r linkfn("persp", pkg = "graphics") function, but with greater flexibility. First, any of x, y or z can be specified using matrices, not just z. This allows parametric surfaces to be plotted. An even simpler specification is possible: x may be a function, in which case persp3d will work out the grid itself. See r linkfn("persp3d.function", text="?persp3d.function", pkg="rgl") for details. For example, the MASS package estimates Gamma parameters using maximum likelihood in a r linkfn("fitdistr", text="?MASS::fitdistr", pkg="MASS") example. Here we show the log likelihood surface. library(MASS) # from the fitdistr example set.seed(123) x <- rgamma(100, shape = 5, rate = 0.1) fit <- fitdistr(x, dgamma, list(shape = 1, rate = 0.1), lower = 0.001) loglik <- function(shape, rate) sum(dgamma(x, shape=shape, rate=rate, log=TRUE)) loglik <- Vectorize(loglik) xlim <- fit$estimate[1]+4*fit$sd[1]*c(-1,1) ylim <- fit$estimate[2]+4*fit$sd[2]*c(-1,1) mfrow3d(1, 2, sharedMouse = TRUE) persp3d(loglik, xlim = xlim, ylim = ylim, n = 30) zlim <- fit$loglik + c(-qchisq(0.99, 2)/2, 0) next3d() persp3d(loglik, xlim = xlim, ylim = ylim, zlim = zlim, n = 30)

On the left, the whole surface over a range of the parameters; on the right, only the parts of the surface with log likelihood values near the maximum.

Note: this example used the knitr hook functions (see r linkfn("setupKnitr")) to insert the scene into this vignette; the previous example used the rglwidget function. We generally recommend the newer r linkfn("rglwidget") approach.

Note that both plot3d and persp3d are generic functions, with the following methods defined:

methods(plot3d) methods(persp3d)

### Primitive shapes

Just as we have r linkfn("points", pkg="graphics") and r linkfn("lines", pkg="graphics") in classic graphics, there are a number of low level functions in rgl to add graphical elements to the currently active plot. The "primitive" shapes are those that are native to OpenGL:

Function Description
r indexfns("points3d"): adds points
r indexfns("lines3d"): adds lines
r indexfns("segments3d"): adds line segments
r indexfns("triangles3d"): adds triangles
r indexfns("quads3d"): adds quadrilaterals

Each of the above functions takes arguments x, y and z, again using r linkfn("xyz.coords", pkg="grDevices") for flexibility. They group successive entries as necessary. For example, the r linkfn("triangles3d") function takes each successive triple of points as the vertices of a triangle.

You can use these functions to annotate the current graph, or to construct a figure from scratch.

### Constructed shapes

rgl also has a number of objects which it constructs from the primitives.

Function Description
r indexfns(c("text3d", "texts3d")): adds text
r indexfns("abclines3d"): adds straight lines to plot (like abline)
r indexfns("arc3d"): adds spherical arcs or spirals to plot
r indexfns("planes3d"): adds planes to plot
r indexfns("clipplanes3d"): add clipping planes to plot
r indexfns(c("sprites3d", "particles3d")): add sprites (fixed shapes or images) to plot
r indexfns("spheres3d"): adds spheres
r indexfns(c("surface3d", "terrain3d")): a surface (as used in r linkfn("persp3d"))
r indexfns("arrow3d"): add an arrow to a scene
r indexfns("pch3d"): draw base-style plotting symbols
r indexfns("plotmath3d"): used by r linkfn("text3d") for math text

### Axes and other "decorations"

The following low-level functions control the look of the graph:

Function Description
r indexfns(c("axes3d", "axis3d")): add axes to plot
r indexfns(c("box3d", "bbox3d")): add box around plot
r indexfns("title3d"): add title to plot
r indexfns("mtext3d"): add marginal text to plot
r indexfns("decorate3d"): add multiple "decorations" (scales, etc.) to plot
r indexfns("aspect3d"): set the aspect ratios for the plot
r indexfns(c("bg3d", "bgplot3d")): set the background of the scene
r indexfns("show2d"): show a 2D plot or image in a 3D scene
r indexfns("legend3d"): set a legend for the scene
r indexfns("grid3d"): add a reference grid to a graph
r indexfns("thigmophobe3d"): choose label positions to avoid overlap

For example, to plot three random triangles, one could use

triangles3d(cbind(x=rnorm(9), y=rnorm(9), z=rnorm(9)), col = "green") decorate3d() bg3d("lightgray") aspect3d(1,1,1)

Besides the *3d functions mentioned above, there are even lower-level functions r indexfns(c("rgl.primitive", "rgl.points", "rgl.linestrips", "rgl.lines", "rgl.triangles", "rgl.quads", "rgl.texts", "rgl.abclines", "rgl.planes", "rgl.bg", "rgl.clipplanes", "rgl.bbox", "rgl.spheres", "rgl.sprites", "rgl.surface")).
You should avoid using these functions, which do not work well with the higher level *3d functions. See the r linkfn("r3d", text="?r3d", pkg="rgl") help topic for details.

## Controlling the Look of the Scene

### Lighting

In most scenes, objects are "lit", meaning that their appearance depends on their position and orientation relative to lights in the scene. The lights themselves don't normally show up, but their effect on the objects does.

Use the r indexfns("light3d") function to specify the position and characteristics of a light. Lights may be infinitely distant, or may be embedded within the scene. Their characteristics include ambient, diffuse, and specular components, all defaulting to white. The ambient component appears the same from any direction. The diffuse component depends on the angle between the surface and the light, while the specular component also takes the viewer's position into account.

The r indexfns("rgl.light") function is a lower-level function with different defaults; users should normally use r linkfn("light3d").

### Materials

The mental model used in rgl is that the objects being shown in scenes are physical objects in space, with material properties that affect how light reflects from them (or is emitted by them). These are mainly controlled by the r indexfns("material3d") function, or by arguments to other functions that are passed to it.

The material properties that can be set by calls to material3d are described in detail in the r linkfn("material3d", text="?material3d", pkg="rgl") help page. Here we give an overview.

Property Default Meaning
color white vector of surface colors to apply to successive vertices for diffuse light
alpha 1 transparency: 0 is invisible, 1 is opaque
lit TRUE whether lighting calculations should be done
ambient black color in ambient light
specular white color in specular light
emission black color emitted by the surface
shininess 50 controls the specular lighting: high values look shiny
smooth TRUE whether shading should be interpolated between vertices
texture NULL optional path to a "texture" bitmap to be displayed on the surface
front, back fill should polygons be filled, or outlined?
size 3 size of points in pixels
lwd 1 width of lines in pixels

Other properties include "texmipmap", "texmagfilter", "texminfilter", "texenvmap", "fog", "point_antialias", "line_antialias", "depth_mask", "depth_test" and "polygon_offset"; see r linkfn("material3d", "the help page", pkg = "rgl") for details.

There is also an r indexfns("rgl.material") function that works at a lower level; users should normally avoid it.

### Textures

As described in the previous section, one of the material properties is texture, the name of a bitmap file (in .png format) containing an image to be displayed on the surface. This section gives more details about textures.

In OpenGL, each vertex in a polygon may be associated with a particular location in the bitmap. The interior of the polygon interpolates within the bitmap. There are two conventions in rgl functions for specifying these coordinates.

Functions which specify primitives (r linkfn("triangles3d"), etc.) accept an optional matrix argument texcoords which gives s (horizontal) and t (vertical) locations within the bitmap in columns with one row per vertex. The coordinates are (0,0) for the lower left, and (1,1) for the upper right. If values outside this range are given, the image repeats, i.e. (1.1, 1.1) would specify the same point in the image as (0.1, 0.1).

Other functions such as r linkfn("surface3d") that take matrices for each vertex coordinate accept texture coordinates as matrices as well, in arguments texture_s and texture_t.

For example, the following code displays four copies of a 2D plot on a quad, because the texture coordinates run from 0 to 2 in both s and t:

filename <- tempfile(fileext = ".png") png(filename = filename) plot(rnorm(1000), rnorm(1000)) dev.off() open3d() xyz <- cbind(c(0,1,1,0), 0, c(0,0,1,1)) quads3d(xyz, texture = filename, texcoords = xyz[,c(1, 3)]*2, col = "white", specular = "black") rglwidget()

Some other notes:

• The color in the figure above was specified to be white. By default, the colors in the bitmap will modify the colour of the quad. If col is black (a common default), you won't see anything.
• On the other hand, you usually don't want specular reflections (which show up as glare). Setting specular to black prevents those.
• How the bitmap is handled is controlled by the material property "textype". The default is "rgb", which takes the red-green-blue colours from the bitmap and uses them to modify the corresponding colours in the polygon. Other possibilities for "textype" are described in r linkfn("material3d", "the material3d help page", pkg = "rgl").
• The other "tex*" material properties control how the interpolation within the image is done.
• Modern OpenGL supports 1- and 3-dimensional textures; these are not supported in rgl.

### par3d: Miscellaneous graphical parameters

The r indexfns("par3d") function, modelled after the classic graphics r linkfn("par", pkg="graphics") function, sets or reads a variety of different rgl internal parameters. Some parameters are completely read-only; others are fixed at the time the window is opened, and others may be changed at any time.

Name Changeable? Description
antialias fixed Amount of hardware antialiasing
cex Default size for text
family Device-independent font family name; see r linkfn("text3d", text="?text3d", pkg="rgl")
font Integer font number
useFreeType Should FreeType fonts be used if available?
fontname read-only System-dependent font name set by r indexfns("rglFonts")
FOV Field of view, in degrees. Zero means isometric perspective
ignoreExtent Should rgl ignore the size of new objects when computing the bounding box?
skipRedraw Should rgl suppress updates to the display?
maxClipPlanes read-only How many clip planes can be defined?
modelMatrix read-only The OpenGL ModelView matrix; partly set by r indexfns("view3d") or the obsolete r indexfns("rgl.viewpoint")
projMatrix read-only The OpenGL Projection matrix
bbox read-only Current bounding-box of the scene
viewport Dimensions in pixels of the scene within the window
windowRect Dimensions in pixels of the window on the whole screen
listeners Which subscenes respond to mouse actions in the current one
mouseMode What the mouse buttons do. See r linkfn("mouseMode", '<code>"mouseMode"</code>')
observer read-only The position of the observer; set by r indexfns("observer3d")
scale Rescaling for each coordinate; see r linkfn("aspect3d")
zoom Magnification of the scene

### Default settings

The r indexfns("r3dDefaults") list and the r indexfns("getr3dDefaults") function control defaults in new windows opened by r linkfn("open3d").
The function looks for the variable in the user's global environment, and if not found there, finds the one in the rgl namespace. This allows the user to override the default settings for new windows.

Once found, the r3dDefaults list provides initial values for r linkfn("par3d") parameters, as well as defaults for r linkfn("material3d") and r linkfn("bg3d") in components "material" and "bg" respectively.

## Meshes: Constructing Shapes

rgl includes a number of functions to construct and display various solid shapes. These generate objects of class "shape3d", "mesh3d" or "shapelist3d". The details of the classes are described below. We start with functions to generate them.

### Specific solids

These functions generate specific shapes. Optional arguments allow attributes such as colour or transformations to be specified.

Function Description
r indexfns(c("tetrahedron3d", "cube3d", "octahedron3d", "dodecahedron3d", "icosahedron3d")): Platonic solids
r indexfns(c("cuboctahedron3d", "oh3d")): other solids
open3d() cols <- rainbow(7) layout3d(matrix(1:16, 4,4), heights=c(1,3,1,3)) text3d(0,0,0,"tetrahedron3d"); next3d() shade3d(tetrahedron3d(col=cols[1])); next3d() text3d(0,0,0,"cube3d"); next3d() shade3d(cube3d(col=cols[2])); next3d() text3d(0,0,0,"octahedron3d"); next3d() shade3d(octahedron3d(col=cols[3])); next3d() text3d(0,0,0,"dodecahedron3d"); next3d() shade3d(dodecahedron3d(col=cols[4])); next3d() text3d(0,0,0,"icosahedron3d"); next3d() shade3d(icosahedron3d(col=cols[5])); next3d() text3d(0,0,0,"cuboctahedron3d"); next3d() shade3d(cuboctahedron3d(col=cols[6])); next3d() text3d(0,0,0,"oh3d"); next3d() shade3d(oh3d(col=cols[7]))

A very large collection of polyhedra is contained in the r linkfn("Rpolyhedra-package", text = "Rpolyhedra", pkg = "Rpolyhedra") package.

### Generating new shapes

These functions generate new shapes:

Function Description
r indexfns("cylinder3d"): generate a tube or cylinder
r indexfns("polygon3d"): generate a flat polygon by triangulation
r indexfns("extrude3d"): generate an "extrusion" of a polygon
r indexfns("turn3d"): generate a solid of rotation
r indexfns("ellipse3d"): generate an ellipsoid in various ways
r indexfns(c("tmesh3d", "qmesh3d")): generate a shape from vertices and faces
r indexfns("shapelist3d"): generate a shape by combining other shapes
as.mesh3d: a generic function; see below

A related function is r indexfns("triangulate"), which takes a two dimensional polygon and divides it up into triangles using the "ear-clipping" algorithm.

The generic function r indexfns("as.mesh3d") is provided to allow data structures produced by other code to be converted to mesh structures. Currently the following classes are supported:

Class Package Description
r indexfns("deldir", pkg = "deldir") deldir Delaunay triangulations of irregular point clouds
r indexfns("triSht", pkg = "interp") interp Also Delaunay triangulations
r indexfns("tri", pkg = "tripack") tripack Generalized Delaunay triangulations
r indexfns("ashape3d", pkg = "alphashape3d") alphashape3d Alpha-shapes
r indexfns("rglId") rgl rgl object identifiers

The default r indexfns("as.mesh3d.default") method is a simple way to construct a mesh from a matrix of vertices; it can use r indexfns("mergeVertices") (which can also be used on its own) to merge repeated vertices within the matrix, allowing r linkfn("addNormals") to be used to give a smooth appearance.

### The underlying class structure for shapes

"shape3d" is the basic abstract type. Objects of this class can be displayed by r indexfns("shade3d") (which shades faces), r indexfns("wire3d") (which draws edges), or r indexfns("dot3d") (which draws points at each vertex.)

"mesh3d" is a descendant type. Objects of this type contain the following fields:

Field Meaning
vb A 4 by n matrix of vertices in homogeneous coordinates. Each column is a point.
it (optional) A 3 by t matrix of vertex indices. Each column is a triangle.
ib (optional) A 4 by q matrix of vertex indices. Each column is a quadrilateral.
material (optional) A list of material properties.
normals (optional) A matrix of the same shape as vb, containing normal vectors at each vertex.
texcoords (optional) A 2 by n matrix of texture coordinates corresponding to each vertex.

### Manipulating shapes

The final set of functions manipulate and modify mesh objects:

Function Description
r indexfns("addNormals"): add normal vectors to make a shape look smooth
r indexfns("subdivision3d"): add extra vertices to make it look even smoother
r indexfns("clipMesh3d"): clip mesh object using curved boundary

The individual steps in r linkfn("subdivision3d") are also available: r indexfns(c("deform.mesh3d", "divide.mesh3d", "normalize.mesh3d")). These are mainly intended for internal use.

## Multi-figure Layouts

rgl has several functions to support displaying multiple different "subscenes" in the same window. The high level functions are

Function Description
r indexfns("mfrow3d"): Multiple figures (like r linkfn("par", text = 'par("mfrow")', pkg="graphics")
r indexfns("layout3d"): Multiple figures (like r linkfn("layout", pkg="graphics"))
r indexfns("next3d"): Move to the next figure (like r linkfn("plot.new", pkg="graphics") or r linkfn("frame", pkg="graphics"))
r indexfns("subsceneList"): List all the subscenes in the current layout
r indexfns("clearSubsceneList"): Clear the current list and revert to the previous one

There are also lower level functions.

Function Description
r indexfns("newSubscene3d"): Create a new subscene, with fine control over what is inherited from the parent
r indexfns("currentSubscene3d"): Report on the active subscene
r indexfns("subsceneInfo"): Get information on current subscene
r indexfns("useSubscene3d"): Make a different subscene active
r indexfns(c("addToSubscene3d", "delFromSubscene3d")): Add objects to a subscene, or delete them
r indexfns("gc3d"): Do "garbage collection": delete objects that are not displayed in any subscene

## Utility Functions

### User interaction

By default, rgl detects and handles mouse clicks within your scene, and uses these to control its appearance. You can find out the current handlers using the following code:

par3d("mouseMode")

The labels c("left", "right", "middle") refer to the buttons on a three button mouse, or simulations of them on other mice. "wheel" refers to the mouse wheel.

The button actions generally correspond to click and drag operations. Possible values for r indexfns("mouseMode", '<code>"mouseMode"</code>') for buttons or the wheel are as follows:

Mode Description
"none" No action
"trackball" The mouse acts as a virtual trackball. Clicking and dragging rotates the scene
"xAxis", "yAxis", "zAxis" Like "trackball", but restricted to rotation about one axis
"polar" The mouse affects rotations by controlling polar coordinates directly
"selecting" The mouse is being used by the r linkfn("select3d") function
"zoom" The mouse zooms the display
"fov" The mouse affects perspective by changing the field of view
"pull" Rotating the mouse wheel towards the user "pulls the scene closer"
"push" The same rotation "pushes the scene away"
"user" A user action set by r indexfns(c("rgl.setMouseCallbacks", "rgl.setWheelCallback")). Use r indexfns("rgl.getMouseCallbacks") and r indexfns("rgl.getWheelCallback") to retrieve

The following functions make use of the mouse for selection within a scene.

Function Description
r indexfns("identify3d"): like the classic graphics r linkfn("identify", pkg="graphics") function
r indexfns("select3d"): returns a function that tests whether a coordinate was selected
r indexfns("selectpoints3d"): selects from specific objects

The r indexfns("rgl.select3d") function is an obsolete version of select3d, and r indexfns("rgl.select") is a low-level support function.

### Animations

rgl has several functions that can be used to construct animations. These are based on functions that update the scene according to the current real-world time, and repeated calls to those. The functions are:

Function Description
r indexfns("play3d"): Repeatedly call the update function
r indexfns("spin3d"): Update the display by rotating at a constant rate
r indexfns("par3dinterp"): Compute new values of some r linkfn("par3d") parameters by interpolation over time

See the r linkfn("movie3d") function for a way to output an animation to a file on disk.
Animations are not currently supported in the HTML written by r linkfn("rglwidget"), though the playwidget function provides equivalent functionality.

### Integration with TCL/TK

There are three functions in rgl that support control of an rgl scene using the TCL/TK framework.

Function Description
r indexfns("tkspin3d"): Set up buttons in a window to control a scene
r indexfns("tkspinControl"): Embed the control buttons in a separate TCL/TK frame
r indexfns("tkpar3dsave"): Create a dialog to interactively save mouse actions

These functions were formerly contained (without the tk prefixes on their names) in the tkrgl package. That package is now deprecated.

### Exporting and importing scenes

rgl contains several functions to write scenes to disk for use by other software, or to read them in.

In order from highest fidelity to lowest, the functions are:

Function Description
r indexfns("scene3d"): Save a scene to an R variable, which can be saved and reloaded
r indexfns("rglwidget"): Prints as HTML and Javascript to display a scene in a web browser. (See also User Interaction in WebGL.)
r indexfns("writeWebGL"): Deprecated.
r indexfns("writeASY"): Write files for Asymptote
r indexfns("writePLY"): Write PLY files (commonly used in 3D printing)
r indexfns(c("readOBJ", "writeOBJ")): Read or write OBJ files (commonly used in 3D graphics)
r indexfns(c("readSTL", "writeSTL")): Read or write STL files (also common in 3D printing)

There are also functions to save snapshots or other recordings of a scene, without any 3D information being saved:

Function Description
r indexfns("snapshot3d"): Save a PNG file bitmap of the scene
r indexfns("rgl.postscript"): Save a Postscript, LaTeX, PDF, SVG or PGF vector rendering of the scene
r indexfns("movie3d"): Save a series of bitmaps to be assembled into a movie
r indexfns("rgl.pixels"): Obtain pixel-level information about the scene in an R variable
r indexfns("rgl.Sweave"): Driver function for inserting a snapshot into a Sweave document.
r indexfns(c("hook_rgl", "hook_webgl")): knitr hook functions for inserting images into a document.
r indexfns("setupKnitr"): Function to set up knitr hooks

The r indexfns("rgl.snapshot") function is identical to snapshot3d. The functions r indexfns(c("rgl.Sweave.off", "Sweave.snapshot")) are involved in Sweave processing and not normally called by users.

### Default display

There are two ways in which rgl scenes are normally displayed within R. The older one is in a dedicated window. In Unix-alikes this is an X11 window; it is a native window in Microsoft Windows. On MacOS, the XQuartz system (see http://xquartz.org) needs to be installed to support this.

To suppress this display, set options(rgl.useNULL = TRUE) before opening a new rgl window. See the help page for the r indexfns("rgl.useNULL") function for how to set this before starting R.

The newer way to display a scene is by using WebGL in a browser window or in the Viewer pane in RStudio. To select this, set options(rgl.printRglwidget = TRUE). Each operation that would change the scene will return a value which triggers a new WebGL display when printed.

### Working with WebGL scenes

There are currently two schemes for exporting a scene to a web page.

The recommended approach works with the htmlwidgets framework (see http://www.htmlwidgets.org/). In an R Markdown document in knitr, use the r indexfns("rglwidget") function. (You can also use chunk option webgl=TRUE; we recommend the explicit use of rglwidget.) This approach also allows display of rgl scenes in RStudio. Besides rgl scenes, various controls for them can be displayed, and there are a few utility functions that can be useful:

Function Description
r indexfns("propertyControl"): set individual properties
r indexfns("clipplaneControl"): control a clippling plane
r indexfns("subsetControl"): control which objects are displayed
r indexfns("ageControl"): "age" vertices of an object
r indexfns("vertexControl"): control properties of vertices
r indexfns("par3dinterpControl"): WebGL control like r linkfn("par3dinterp")
r indexfns("playwidget"): display and automate controls
r indexfns("toggleWidget"): display a button to toggle some items
r indexfns("sceneChange"): used in Shiny for large scene changes
r indexfns(c("shinyGetPar3d", "shinySetPar3d")): get or set r linkfn("par3d") values from Shiny
r documentedfns <- c(documentedfns, "%>%");indexfns("pipe", text="%>%"): magrittr pipe
r indexfns(c("figHeight", "figWidth")): Dimensions of figures in R Markdown document
r indexfns("rglShared"): share data using crosstalk package
r indexfns("rglMouse"): change mouse mode in rgl scene
r indexfns("asRow"): arrange multiple objects in an HTML display
r indexfns("getWidgetId"): get the elementId from a widget

Some functions are mainly for internal use: r indexfns(c("elementId2Prefix", "playwidgetOutput", "renderPlaywidget", "rglwidgetOutput", "renderRglwidget", "registerSceneChange")). More details are given in the vignette User Interaction in WebGL. The functions r indexfns(c("lowlevel", "highlevel", "rglId")) are also for internal use, marking function results for automatic printing. Finally, the experimental function r indexfns("setUserShaders") allows you to use hand-written shaders in WebGL.

The older approach uses the writeWebGL function to export a scene to HTML and Javascript code.
The functions below write HTML and Javascript for working with the exported scene.

Function Description
r indexfns("propertySlider"): insert a slider to make changes to a scene
r indexfns("clipplaneSlider"): insert a slider to control a clipping plane
r indexfns("subsetSlider"): insert a slider to control which objects are displayed
r indexfns("toggleButton"): insert a button to toggle some items
r indexfns("propertySetter"): function to modify properties
r indexfns("subsetSetter"): function to choose subsets
r indexfns("ageSetter"): function to "age" vertices
r indexfns("par3dinterpSetter"): function like r linkfn("par3dinterp")
r indexfns("vertexSetter"): function to modify individual vertices
r indexfns("matrixSetter"): function to modify matrices

### Working with the scene

rgl maintains internal structures for all the scenes it displays. The following functions allow users to find information about them and manipulate them.

Function Description
r indexfns("open3d"): open a new window
r indexfns("rgl.close"): close the current window
r indexfns("rgl.bringtotop"): bring the current window to the top
r indexfns("rgl.cur"): id of the active device
r indexfns("rgl.dev.list"): ids of all active devices
r indexfns("rgl.set"): set a particular device to be active
r indexfns("rgl.ids"): ids and types of all current objects
r indexfns(c("rgl.attrib", "rgl.attrib.info", "rgl.attrib.count")): attributes of objects in the scene
r indexfns(c("pop3d", "rgl.pop")): delete an object from the scene
r indexfns(c("clear3d", "rgl.clear")): delete all objects of certain classes
r indexfns("rgl.projection"): return information about the current projection
r indexfns(c("rgl.user2window", "rgl.window2user")): convert between coordinates in the current projection

The r indexfns("as.triangles3d") generic function is intended to extract coordinates in a form suitable for passing to r linkfn("triangles3d"). Currently a method is provided for r linkfn("rglId") objects.

In addition to these, there are some other related functions which should rarely be called by users: r indexfns(c("rgl.init", "rgl.open", "rgl.quit")).

### Working with 3-D vectors

Most rgl functions work internally with "homogeneous" coordinates. In this system, 3-D points are represented with 4 coordinates, generally called (x, y, z, w). The corresponding Euclidean point is (x/w, y/w, z/w), if w is nonzero; zero values of w correspond to "points at infinity". The advantage of this system is that affine transformations including translations and perspective shifts become linear transformations, with multiplication by a 4 by 4 matrix.

rgl has the following functions to work with homogeneous coordinates:

Function Description
r indexfns(c("asEuclidean", "asHomogeneous")): convert between homogeneous and Euclidean coordinates
r indexfns(c("rotate3d", "scale3d", "translate3d")): apply a transformation
r indexfns("transform3d"): apply a general transformation
r indexfns(c("rotationMatrix", "scaleMatrix", "translationMatrix")): compute the transformation matrix
r indexfns("identityMatrix"): return a 4 x 4 identity matrix

There is also a function r indexfns("GramSchmidt"), mainly for internal use: it does a Gram-Schmidt orthogonalization of a 3x3 matrix, with some specializations for its use in r linkfn("cylinder3d").

### Working with other packages

Sometimes it may be convenient to interactively rotate a scene to a particular view, then display it in lattice or base graphics. The r indexfns("rglToLattice") and r indexfns("rglToBase") functions support this.

For example, we first display the volcano data in rgl:

rgl.close() persp3d(volcano, col = "green") rglwidget()

This display is interactive, but we can reproduce the initial view using the lattice r linkfn("wireframe", pkg = "lattice") or base graphics r linkfn("persp", pkg = "graphics") functions:

lattice::wireframe(volcano, col = "green", screen = rglToLattice()) angles <- rglToBase() persp(volcano, col = "green", shade = TRUE, theta = angles$theta, phi = angles$phi)

Note that the orientlib package must be available for these functions to work.

## Warning: Work in Progress!

This vignette is always a work in progress. Some aspects of the rgl package are not described, or do not have examples. There may even be functions that are missed completely, if the following list is not empty:

setdiff(ls("package:rgl"), documentedfns)

## Index of Functions

The following functions and constants are described in this document:

writeIndex(cols = 5)