vwline (version 0.2-2)

grid.offsetBezier: Draw a Bezier Offset Curve.

Description

Draw a Bezier offset curve; the main curve is described by x/y control points and offset Bezier curves are calculated to the left and right of the main curve at the specified widths.

Usage

offsetBezierGrob(x, y, w, default.units="npc", 
                 stepFn=nSteps(100), open=TRUE,
                 lineend="butt", linejoin="round", mitrelimit=4,
                 render=if (open) vwPolygon else vwPath(),
                 gp=gpar(fill="black"), name=NULL, debug=FALSE)
grid.offsetBezier(...)

Value

grid.offsetBezier is used for its side-effect of drawing a variable-width line; offsetBezierGrob returns a "offsetBezierGrob" object.

Arguments

x

A numeric vector or unit describing x-locations.

y

A numeric vector or unit describing y-locations.

w

A numeric vector or unit describing widths at each location, or a width specification generated by widthSpline or a width specification generated by BezierWidth.

default.units

The units used if x or y are numeric vectors.

stepFn

Function called to generate steps in t when rendering. See Details.

open

A boolean indicating whether to connect the last location back to the first location to produce a closed line.

lineend

The line ending style; one of "round", "mitre", "butt", "square", or "extend".

linejoin

The line join style; one of "round", "mitre", "bevel", or "extend".

mitrelimit

A numeric that controls when a mitre join is converted to a bevel join or a mitre ending is converted to a square ending.

render

A function that is used to render the outline of the path that is generated for the variable-width line.

gp

A set of graphical parameters; see gpar.

name

A name for the grob generated for the variable-width line.

debug

A logical indicating whether to produce graphical debugging output.

...

Arguments passed to offsetBezierGrob.

Author

Paul Murrell

Details

Rendering relies on flattening the spline to a series of straight line segments. This depends on generating a set of t values (and then x and y are calculated from t). The stepFn is called to generate t and given the control points, x and y as arguments, plus a range, which indicates what range of t to generate values for.

The "extend" line ending and line join style is only available if the width is specified by BezierWidth.

See Also

grid.xspline, grid.vwline, grid.vwcurve, grid.brushXspline, grid.vwXspline, grid.offsetXspline

Examples

grid.newpage()
x <- c(.2, .4, .6, .8)
y <- c(-.05, .05, -.05, .05)
w <- unit(c(2, 4, 6, 8), "mm")
grid.offsetBezier(x, y + .8, w)
grid.offsetBezier(x, y + .5, w,
                  lineend="round")
grid.offsetBezier(x, y + .2, w,
                  gp=gpar(col="black"), debug=TRUE)