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Calculate x,y,z coordinates from a height matrix

Source: R/xyz_heightmap.R
xyz_heightmap.Rd

Calculate x,y,z coordinates from a height matrix

Usage

xyz_heightmap(
  mat,
  col = NULL,
  scale = 1,
  min = NULL,
  flipx = FALSE,
  flipy = TRUE,
  ground = "xy",
  solid = TRUE,
  verbose = FALSE
)

Arguments

mat

integer matrix. The matrix will be interpreted as cubes (or cuboids) flat on the page, with the value in the matrix interpreted as the height above the page.

col

matrix, vector, or (palette) function of colours. If a matrix it must be the same dimensions as the mat argument; each cube/cuboid corresponding to that x,y value will have that color. If a vector then if the max of z values is less than equal to the number of colors we will use the z integers as indices else we will use base::cut() to assign z values to colors. If a function we will call it with the argument max(z) to create a a vector of colors and then use the z values as indices. If col is not NULL then a fill column will be included in the final returned coordinates.

scale

scale factor for values in matrix. Default = 1

min

Minimum target z value. If NULL ignore else we "translate" the z-values so the minimum z-value is equal to this value.

flipx, flipy

Should the matrix be flipped in the horizontal/vertical directions (respectively)? Note: flipy defaults to TRUE as matrices are indexed from the top-down, but the coordinate space is increasing from the bottom up. Flipping the matrix vertically is usually what you want.

ground

Orientation of the ground plane. Default: "xy". Possible values "xy", "xz", "zy"

solid

Should the heightmap be made 'solid' i.e. without holes? This can be an expensive operation in terms of both memory and CPU, but should be OK for simple examples. Set to FALSE if things take too long or you will be rendering cuboids. This operation works by extruding cubes down from the top of the height map to the floor to ensure gaps do not appear when the slope is too great.

verbose

Be verbose? default: FALSE

Value

A data frame of x, y, z, raw, and possibly fill columns. The "raw" column is the (original) "z" column before any scale, min, and ground transformations have been performed (it may be repeated "down" if solid = TRUE). The "raw" column can be useful as the fill value in ggplot2 plots especially when adding a legend.

Examples

if (require("grDevices") && require("grid")) {
  mat <- datasets::volcano
  mat <- 0.3 * (mat - min(mat)) + 1.0

  grid.newpage()
  grid.rect(gp=gpar(col=NA, fill="grey5"))
  width <- convertWidth(unit(0.007, "snpc"), "cm")

  # Top view
  pushViewport(viewport(width = 0.7, height = 0.7, x = 0.65, y = 0.65))
  coords <- xyz_heightmap(mat, col = terrain.colors, solid = FALSE)
  grid.oblicubes(coords, scale = 0, width = width, gp = gpar(col=NA))
  popViewport()

  # South view
  pushViewport(viewport(width = 0.7, height = 0.3, x = 0.65, y = 0.15))
  coords <- xyz_heightmap(mat, col = terrain.colors, ground = "xz")
  grid.oblicubes(coords, scale = 0, width = width, gp = gpar(col=NA))
  popViewport()

  # West view
  pushViewport(viewport(width = 0.3, height = 0.7, x = 0.15, y = 0.65))
  coords <- xyz_heightmap(mat, col = terrain.colors, ground = "zy")
  grid.oblicubes(coords, scale = 0, width = width, gp = gpar(col=NA))
  popViewport()
}

if (require("grDevices") && require("ggplot2")) {
  data("volcano", package = "datasets")
  df <- xyz_heightmap(volcano, scale = 0.3, min = 1, solid = FALSE)
  g <- ggplot(df, aes(x, y, z = z, fill = raw)) +
         geom_oblicuboids(light = FALSE) +
         coord_fixed() +
         scale_fill_gradientn(name = "Height (m)", colours=terrain.colors(256)) +
         labs(x = "East (10m)", y = "North (10m)", title = "Maungawhau (`datasets::volcano`)")
  plot(g)
}