writeWebGL: Write scene to HTML.

In trestletech/rgl: 3D visualization device system (OpenGL)

Description

Writes the current scene to a collection of files that contain WebGL code to reproduce it in a browser.

Usage

writeWebGL(dir = "webGL", filename = file.path(dir, "index.html"), 
           template = system.file(file.path("WebGL", "template.html"), package = "rgl"),
           prefix = "",
           snapshot = TRUE, commonParts = TRUE, reuse = NULL, 
           font = "Arial", width, height)

Arguments

dir	Where to write the files.
filename	The filename to use for the main file.
template	The template web page to which to write the Javascript for the scene. See Details below.
prefix	An optional prefix to use on global identifiers in the scene; use different prefixes for different scenes displayed on the same web page. If not blank, it should be a legal identifier in Javascript and HTML.
snapshot	Whether to include a snapshot of the scene, to be displayed in browsers that don't support WebGL.
commonParts	Whether to include parts that would be common to several figures on the same page. Currently this includes a reference to and copy of the ‘CanvasMatrix.js’ file in the output.
reuse	When writing several figures on the same page, set this to a dataframe containing values to reuse. See the Value section below.
font	The font to use for text.
width, height	The (optional) width and height in pixels of the image to display. If omitted, the par3d("windowRect") dimensions will be used.

Details

This function writes out a web page containing Javascript that reconstructs the scene in WebGL.

Use the template argument to give the filename of a web page that is to contain the code for the new scene. It should contain a single line containing paste0("%", prefix, "WebGL%"), e.g. %WebGL% with the default empty prefix. That line will be replaced by the Javascript and other code necessary to reproduce the current scene. The template may also contain the string "%rglVersion%" which will be replaced with the current rgl version number. If template is NULL, the output will simply be written directly to the main file.

To put more than one scene into a web page, use different values of prefix for each. The prefix will be used in identifiers in both Javascript and HTML, so it is safest to start with a letter and only use alphanumeric characters.

WebGL is a fairly new technology for displaying 3D scenes in browsers. Most current browsers support it to some extent, though it may not be enabled by default; see http://get.webgl.org for details. A major exception currently is Microsoft's Internet Explorer, though plugins are available.

Currently writeWebGL has a number of known limitations, some of which will be gradually eliminated as development progresses:

• The bounding box decorations are fixed; labels do not move as they do within R.

• User-defined mouse controls are not supported.

• No automatic movement (e.g. rotation via spin3d) is supported.

• Missing values are not handled properly.

• Polygons will only be rendered as filled; there is no support in WebGL for wireframe or point rendering.

• WebGL browsers generally do not support more than 65535 vertices per object. writeWebGL will print a warning if this limit is exceeded, but it is up to the user to break his scene into smaller objects. (And 65535 vertices may not be small enough!)

There is some experimental support for modification of the scene by other Javascript code on the same web page. Currently this is limited to the following. There will be a global variable created with name <prefix>rgl, where <prefix> will be replaced by the prefix argument to writeWebGL. Currently this variable will contain properties corresponding to some of the components returned by par3d, namely FOV, zoom, userMatrix and listeners. Each of these components should be indexed by a subscene number to obtain the value for that subscene; for example, use <prefix>rgl.userMatrix[3] to obtain the user matrix for subscene 3 as a CanvasMatrix4 object (defined in the ‘CanvasMatrix.js’ library). After modifying any of these values, user code should insert a call <prefix>rgl.drawScene(); to update the display.

Value

The filename is returned. If reuse is not NULL, it will have an attribute called "reuse" which contains a dataframe with columns "id" and "prefix" identifying the prefix used for objects drawn in this scene. This dataframe can be used as the reuse argument in subsequent calls to writeWebGL.

Note

If commonParts is TRUE, the output includes a binary copy of the CanvasMatrix Javascript library. This file is necessary for the Javascript code written by writeWebGL to function properly, but only one copy is needed if the output page contains multiple writeWebGL figures.

Its source (including the copyright notice and license for free use) is included in the file named by system.file("WebGL/CanvasMatrix.src.js", package = "rgl").

Author(s)

Duncan Murdoch.

References

http://www.webgl.org

See Also

scene3d saves a copy of a scene to an R variable; writePLY, writeOBJ and writeSTL write the scene to a file in various other formats.

Examples

plot3d(rnorm(100), rnorm(100), rnorm(100), type = "s", col = "red")
# This writes a copy into temporary directory 'webGL', and then displays it
filename <- writeWebGL(dir = file.path(tempdir(), "webGL"), 
                       width = 500, reuse = TRUE)
# Display the "reuse" attribute
attr(filename, "reuse")

# Display the scene in a browser
if (interactive())
  browseURL(paste0("file://", filename))

trestletech/rgl documentation built on May 31, 2019, 7:49 p.m.