Create a quad-type mesh for use in rgl.

Source: R/discrete.R, R/quadmesh.R

Convert an object to a mesh3d quadrangle mesh, with methods for raster::raster() and matrix.

dquadmesh(
  x,
  z = x,
  na.rm = FALSE,
  ...,
  texture = NULL,
  texture_filename = NULL
)

# Default S3 method
dquadmesh(
  x,
  z = x,
  na.rm = FALSE,
  ...,
  texture = NULL,
  texture_filename = NULL
)

quadmesh(
  x,
  z = x,
  na.rm = FALSE,
  ...,
  texture = NULL,
  texture_filename = NULL,
  maxcell = 50000
)

# S3 method for class 'SpatRaster'
quadmesh(
  x,
  z = x,
  na.rm = FALSE,
  ...,
  texture = NULL,
  texture_filename = NULL,
  maxcell = 50000
)

# S3 method for class 'BasicRaster'
quadmesh(
  x,
  z = x,
  na.rm = FALSE,
  ...,
  texture = NULL,
  texture_filename = NULL,
  maxcell = 50000
)

# S3 method for class 'matrix'
quadmesh(
  x,
  z = x,
  na.rm = FALSE,
  ...,
  texture = NULL,
  texture_filename = NULL,
  maxcell = 50000
)

Arguments

x

raster object for mesh structure

z

raster object for height values

na.rm

remove quads where missing values?

...

ignored

texture

optional input RGB raster (3-layers), or the file path to a PNG image

texture_filename

optional input file path for PNG texture

maxcell

default number of raster or terra cells to plot, with a default lowish-number - set to NULL to use native resolution

Value

mesh3d

Details

quadmesh() generates the cell-based interpretation of a raster (AREA) but applies a continuous interpretation of the values of the cells to each quad corner. dquadmesh splits the mesh and applies a discrete interpretation directly. Loosely, the quadmesh is a continuous surface and the dquadmesh is free-floating cells, but it's a little more complicated and depends on the options applied. (The interpolation) applied in the quadmesh case is not entirely consistent.

The output is described as a mesh because it is a dense representation of a continuous shape, in this case plane-filling quadrilaterals defined by index of four of the available vertices.

The z argument defaults to the input x argument, though may be set to NULL, a constant numeric value, or another raster. If the coordinate system of z and x don't match the z values are queried by reprojection.

Any raster RGB object (3-layers, ranging in 0-255) may be used as a texture on the resulting mesh3d object. If texture is a palette raster it will be auto-expanded to RGB.

It is not possible to provide rgl with an object of data for texture, it must be a PNG file and so the in-memory texture argument is written out to PNG file (with a message). The location of the file may be set explicitly with texture_filename.

Alternatively, texture may be the file path to an existing PNG image, in which case no reprojection or file writing is done: the image is draped over the raster extent with extent-normalized texture coordinates (the semantics of textures::quad_texture()).

Examples

library(raster)
data(volcano)
r <- setExtent(raster(volcano), extent(0, 100, 0, 200))
qm <- quadmesh(r)