Mesh raster

Create a grid by interpolating across triangles.

Usage

mesh_raster(x, grid = NULL, n = 128, ...)

# S3 method for class 'mesh3d'
mesh_raster(x, grid = NULL, n = 128, ...)

# S3 method for class 'matrix'
mesh_raster(x, grid = NULL, n = 128, ...)

# S3 method for class 'data.frame'
mesh_raster(x, grid = NULL, n = 128, ...)

Arguments

x

a matrix or data frame of three columns, or a mesh3d

grid

a grid_spec() to interpolate onto, or NULL for a default one

n

cells across, when grid is not supplied

...

passed to methods, and on to grid_barycentric()

Value

A guerrilla_grid with values.

Details

For x-y-z input this is grid_barycentric() with the arguments arranged differently: triangulate, then estimate each cell from the triangle containing it. The difference is that mesh_raster() also takes a mesh3d, where the triangles already exist and no triangulation is needed.

That case is worth having because it runs the argument backwards. A grid is one particular mesh – a regular one, with the values at the vertices – so turning an arbitrary mesh into a grid is resampling one mesh onto another, and barycentric interpolation is how you do it either way.

Examples

## interpolate from raw points
xyz <- quakes[c("long", "lat", "depth")]
xyz$depth <- -xyz$depth
gx <- mesh_raster(xyz)
#> 2 duplicated coordinates collapsed with mean()
rat <- 1/cos(mean(xyz[["lat"]]) * pi/180)
plot(gx, asp = rat, col = hcl.colors(12, "YlOrRd"))
points(xyz, pch = "+", cex = 0.3)


## add some dummy points (we aren't modelling the world)
xex <- cbind(expand.grid(long = range(xyz$long),
                         lat = range(xyz$lat)), depth = 0)
g2 <- mesh_raster(rbind(xex, xyz))
#> 2 duplicated coordinates collapsed with mean()
plot(g2, asp = rat)
points(xyz, pch = "+", cex = 0.3)

if (requireNamespace("maps", quietly = TRUE)) {
  maps::map(add = TRUE)
}


## a mesh of triangles, rather than raw points
if (requireNamespace("Rvcg", quietly = TRUE)) {
  data("humface", package = "Rvcg")
  grid <- mesh_raster(humface, n = 256)
  plot(grid, col = grey.colors(24))
}


## and back the other way, in 3D
if (interactive() && requireNamespace("anglr", quietly = TRUE)) {
  anglr::plot3d(as_raster(g2))
  rgl::aspect3d(1, rat, 0.1)
  rgl::points3d(xyz$long, xyz$lat, xyz$depth + 30)
}