persp3d {rgl} | R Documentation

## Surface plots

### Description

This function draws plots of surfaces in 3-space. `persp3d` is a generic function.

### Usage

    persp3d(x, ...)

    ## Default S3 method:
    persp3d(x = seq(0, 1, len = nrow(z)), y = seq(0, 1, len = ncol(z)), z,
        xlim = NULL, ylim = NULL, zlim = NULL,
        xlab = NULL, ylab = NULL, zlab = NULL, add = FALSE, aspect = !add,
        forceClipregion = FALSE, ...)

### Arguments

`x, y, z` | points to plot on surface. See Details below.
`xlim, ylim, zlim` | x-, y- and z-limits. If present, the plot is clipped to this region.
`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.
`forceClipregion` | force a clipping region to be used, whether or not limits are given.
`...` | additional material parameters to be passed to `surface3d` and `decorate3d`.

### Details

The default method plots a surface defined as a grid of `(x,y,z)` locations in space. The grid may be specified in several ways:

- As with `persp`, `x` and `y` may be given as vectors in ascending order, with `z` given as a matrix. There should be one `x` value for each row of `z` and one `y` value for each column. The surface drawn will have `x` constant across rows and `y` constant across columns. This is the most convenient format when `z` is a function of `x` and `y` which are measured on a regular grid.

- `x` and `y` may also be given as matrices, in which case they should have the same dimensions as `z`. The surface will combine corresponding points in each matrix into locations `(x,y,z)` and draw the surface through those. This allows general surfaces to be drawn, as in the example of a spherical Earth shown below.

- If `x` is a `list`, its components `x$x`, `x$y` and `x$z` are used for `x`, `y` and `z` respectively, though an explicitly specified `z` value will have priority.

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`.

See the “Clipping” section in `plot3d` for more details on `xlim, ylim, zlim` and `forceClipregion`.

### Value

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

### Author(s)

Duncan Murdoch

### See Also

`plot3d`, `persp`. There is a `persp3d.function` method for drawing functions, and `persp3d.deldir` can be used to draw surfaces defined by an irregular collection of points. A formula method `persp3d.formula` draws surfaces using this method.

The `surface3d` function is used to draw the surface without the axes etc.

### Examples

    # (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")

    # Draw the surface twice:  the first draws the solid part,
    # the second draws the grid.  Offset the first so it doesn't
    # obscure the first.

    persp3d(x, y, z, aspect = c(1, 1, 0.5), col = "lightblue",
            xlab = "X", ylab = "Y", zlab = "Sinc( r )",
            polygon_offset = 1)
    persp3d(x, y, z, front = "lines", back = "lines",
            lit = FALSE, add = TRUE)

    # (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 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 = 16), duration = 2.5)

    ## Not run:
    # 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)

    ## End(Not run)

[Package rgl version 0.100.19 Index]