Display an apparent cylinder

Display rectangles shaded to appear like cylinders.

Usage

cylindrect(xleft,ybottom,xright,ytop,col,border=NA,gradient="x",nslices=50)

Arguments

xleft: The position of the left side of the rectangle(s).
ybottom: The position of the bottom of the rectangle(s).
xright: The position of the right side of the rectangle(s).
ytop: The position of the top side of the rectangle(s).
col: The base color(s) of the rectangles.
border: Whether to draw a border and what color.
gradient: Whether to vary the shading horizontally ("x" - the default) or vertically (anything but "x").
nslices: The number of "slices" of color for shading.

Value

The base color(s) of the rectangle(s).

Details

cylindrect displays a rectangle filled with "slices" of color that simulate the appearance of a cylinder. The slices are calculated so that the base color appears at the right or bottom edge of the rectangle, becomes progressively lighter to a "highlight" at two thirds of the width or height and then darkens toward the base color again.

The appearance is of a cylinder lit from above and to the left of the viewer. The position of the apparent light source is hard coded into the function.

Author

Jim Lemon

Examples

 plot(0,xlim=c(0,5),ylim=c(0,5),main="Examples of pseudocylindrical rectangles",
  xlab="",ylab="",axes=FALSE,type="n")
 cylindrect(0,0,1,5,"red")
 cylindrect(rep(1,3),c(0,2,4),rep(4,3),c(1,3,5),"green",gradient="y")
 cylindrect(4,0,5,5,"#8844aa")