persp3d: Surface plots

Description

This function draws plots of surfaces over the x-y plane. persp3d is a generic function.

Usage

persp3d(x, ...)
## S3 method for class 'default':
persp3d(x = seq(0, 1, len = nrow(z)), y = seq(0, 1, len = ncol(z)), z,
    xlim = range(x, na.rm = TRUE), 
    ylim = range(y, na.rm = TRUE), 
    zlim = range(z, na.rm = TRUE),
    xlab = NULL, ylab = NULL, zlab = NULL, add = FALSE, aspect = !add, ...)

Arguments

x, y

locations of grid lines at which the values in z are measured. These may be given as vectors or matrices. If vectors, they must be in ascending order. Either one or both may be matrices. If x is a list

a matrix containing the values to be plotted. Note that x can be used instead of z for convenience.

xlim, ylim, zlim

x-, y- and z-limits. The plot is produced so that the rectangular volume defined by these limits is visible.

xlab, ylab, zlab

titles for the axes. N.B. These must be character strings; expressions are not accepted. Numbers will be coerced to character strings.

add

whether to add the points to an existing plot.

aspect

either a logical indicating whether to adjust the aspect ratio, or a new ratio

...

additional material parameters to be passed to surface3d and decorate3d.

Value

This function is called for the side effect of drawing the plot. A vector of shape IDs is returned.

Details

This is similar to persp with user interaction. See plot3d for more general details. One difference from persp is that colors are specified on each vertex, rather than on each facet of the surface. To emulate the persp color handling, you need to do the following. First, convert the color vector to an (nx-1) by (ny-1) matrix; then add an extra row before row 1, and an extra column after the last column, to convert it to nx by ny. (These extra colors will not be used). For example, col <- rbind(1, cbind(matrix(col, nx-1, ny-1), 1)). Finally, call persp3d with material property smooth = FALSE. If the x or y argument is a matrix, then it must be of the same dimension as z, and the values in the matrix will be used for the corresponding coordinates. This is used to plot shapes such as spheres or cylinders where z is not a function of x and y. See the fourth and fifth examples below.

Examples

Run this code

# (1) The Obligatory Mathematical surface.
#     Rotated sinc function.

x <- seq(-10, 10, length= 30)
y <- x
f <- function(x,y) { r <- sqrt(x^2+y^2); 10 * sin(r)/r }
z <- outer(x, y, f)
z[is.na(z)] <- 1
open3d()
bg3d("white")
material3d(col="black")
persp3d(x, y, z, aspect=c(1, 1, 0.5), col = "lightblue",
        xlab = "X", ylab = "Y", zlab = "Sinc( r )")

# (2) Add to existing persp plot:

xE <- c(-10,10); xy <- expand.grid(xE, xE)
points3d(xy[,1], xy[,2], 6, col = "red")
lines3d(x, y=10, z= 6 + sin(x), col = "green")

phi <- seq(0, 2*pi, len = 201)
r1 <- 7.725 # radius of 2nd maximum
xr <- r1 * cos(phi)
yr <- r1 * sin(phi)
lines3d(xr,yr, f(xr,yr), col = "pink", lwd = 2)

# (3) Visualizing a simple DEM model

z <- 2 * volcano        # Exaggerate the relief
x <- 10 * (1:nrow(z))   # 10 meter spacing (S to N)
y <- 10 * (1:ncol(z))   # 10 meter spacing (E to W)

open3d()
bg3d("slategray")
material3d(col="black")
persp3d(x, y, z, col = "green3", aspect="iso",
      axes = FALSE, box = FALSE)

# (4) A cylindrical plot

z <- matrix(seq(0, 1, len=50), 50, 50)
theta <- t(z)
r <- 1 + exp( -pmin( (z - theta)^2, (z - theta - 1)^2, (z - theta + 1)^2 )/0.01 )
x <- r*cos(theta*2*pi)
y <- r*sin(theta*2*pi)

open3d()
persp3d(x, y, z, col="red")

# (5) A globe

lat <- matrix(seq(90,-90, len=50)*pi/180, 50, 50, byrow=TRUE)
long <- matrix(seq(-180, 180, len=50)*pi/180, 50, 50)

r <- 6378.1 # radius of Earth in km
x <- r*cos(lat)*cos(long)
y <- r*cos(lat)*sin(long)
z <- r*sin(lat)

open3d()
persp3d(x, y, z, col="white", 
       texture=system.file("textures/worldsmall.png",package="rgl"), 
       specular="black", axes=FALSE, box=FALSE, xlab="", ylab="", zlab="",
       normal_x=x, normal_y=y, normal_z=z)
if (!rgl.useNULL())
  play3d(spin3d(axis=c(0,0,1), rpm=8), duration=5)

# This looks much better, but is slow because the texture is very big
persp3d(x, y, z, col="white", 
       texture=system.file("textures/world.png",package="rgl"), 
       specular="black", axes=FALSE, box=FALSE, xlab="", ylab="", zlab="",
       normal_x=x, normal_y=y, normal_z=z)

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