This is a low-level function for plotting text. Users should normally use the high-level function text3d instead.

rgl.texts(x, y = NULL, z = NULL, text,
adj = 0.5, pos = NULL, offset = 0.5,
family = par3d("family"), font = par3d("font"),
cex = par3d("cex"), useFreeType = par3d("useFreeType"), ...)
rglFonts(...)

## Arguments

x, y, z

point coordinates. Any reasonable way of defining the coordinates is acceptable. See the function xyz.coords for details.

text

text character vector to draw

one value specifying the horizontal adjustment, or two, specifying horizontal and vertical adjustment respectively, or three, specifying adjustment in all three directions.

pos

a position specifier for the text. If specified, this overrides any adj value given. Values of 0, 1, 2, 3, 4, 5 and 6 respectively indicate positions on, below, to the left of, above, to the right of, in front of and behind the specified coordinates.

offset

when pos is specified, this value gives the offset of the label from the specified coordinate in fractions of a character width.

family

A device-independent font family name, or ""

font

A numeric font number from 1 to 4

cex

A numeric character expansion value

useFreeType

logical. Should FreeType be used to draw text? (See details below.)

...

In rgl.texts, material properties; see rgl.material for details. In rglFonts, device dependent font definitions for use with FreeType.

## Details

The adj parameter determines the position of the text relative to the specified coordinate. Use adj = c(0, 0) to place the left bottom corner at (x, y, z), adj = c(0.5, 0.5) to center the text there, and adj = c(1, 1) to put the right top corner there. All coordinates default to 0.5. Placement is done using the "advance" of the string and the "ascent" of the font relative to the baseline, when these metrics are known.

## Fonts

Fonts are specified using the family, font, cex, and useFreeType arguments. Defaults for the currently active device may be set using par3d, or for future devices using r3dDefaults.

The family specification is the same as for standard graphics, i.e. families
c("serif", "sans", "mono", "symbol")
are normally available, but users may add additional families. font numbers are restricted to the range 1 to 4 for standard, bold, italic and bold italic respectively. Font 5 is recoded as family "symbol" font 1, but that is not supported unless specifically installed, so should be avoided.

Using an unrecognized value for "family" will result in the system standard font as used in RGL up to version 0.76. That font is not resizable and font values are ignored.

If useFreeType is TRUE, then RGL will use the FreeType anti-aliased fonts for drawing. This is generally desirable, and it is the default on non-Windows systems if RGL was built to support FreeType.

FreeType fonts are specified using the rglFonts function. This function takes a vector of four filenames of TrueType font files which will be used for the four styles regular, bold, italic and bold italic. The vector is passed with a name to be used as the family name, e.g. rglFonts(sans = c("/path/to/FreeSans.ttf", ...)). In order to limit the file size, the rgl package ships with just 3 font files, for regular versions of the serif, sans and mono families. Additional free font files were available in the past from the Amaya project, though currently the rglExtrafonts function provides an easier way to register new fonts.

On Windows the system fonts are acceptable and are used when useFreeType = FALSE (the current default in r3dDefaults). Mappings to family names are controlled by the grDevices::windowsFonts() function.

Full pathnames should normally be used to specify font files. If relative paths are used, they are interpreted differently by platform. Currently Windows fonts are looked for in the Windows fonts folder, while other platforms use the current working directory.

If FreeType fonts are not used, then bitmapped fonts will be used instead. On Windows these will be based on the fonts specified using the windowsFonts function, and are resizable. Other platforms will use the default bitmapped font which is not resizable.

Bitmapped fonts have a limited number of characters supported; if any unsupported characters are used, an error will be thrown.

## Value

rgl.texts returns the object ID of the text object (or sprites, in case of usePlotmath = TRUE) invisibly. rglFonts returns the current set of font definitions.

## Examples

if (FALSE) {
# These FreeType fonts are available from the Amaya project, and are not shipped
# with rgl.  You would normally install them to the rgl/fonts directory
# and use fully qualified pathnames, e.g.
# system.file("fonts/FreeSerif.ttf", package = "rgl")

rglFonts(serif = c("FreeSerif.ttf", "FreeSerifBold.ttf", "FreeSerifItalic.ttf",
"FreeSerifBoldItalic.ttf"),
sans  = c("FreeSans.ttf", "FreeSansBold.ttf", "FreeSansOblique.ttf",
"FreeSansBoldOblique.ttf"),
mono  = c("FreeMono.ttf", "FreeMonoBold.ttf", "FreeMonoOblique.ttf",
"FreeMonoBoldOblique.ttf"),
symbol= c("ESSTIX10.TTF", "ESSTIX12.TTF", "ESSTIX9_.TTF",
"ESSTIX11.TTF"))
}