hex_globe() draws a grid on a globe that turns under the
mouse, rendered on the graphics card through WebGPU. Drag to turn the
globe; drag with Shift held to turn the view about the line of sight;
the mouse wheel zooms. The slider folds the polyhedron the grid is built
on into the sphere, and the pointer shows the ID and value of the cell
under it.
The globes on this page need a browser with WebGPU (see Where the globe draws); without it each one shows a notice in its place.
Installation
# Install from CRAN
install.packages("hexify")
# Or install development version from GitHub
# install.packages("pak")
pak::pak("gcol33/hexify")Values per cell
values holds one number per cell of cells,
or one per cell of the grid when cells is
NULL. Here each cell is filled by the latitude of its
centre.
grid <- hex_grid(resolution = 3, aperture = 3)
cells <- seq_len(n_cells(grid))
centres <- cell_to_lonlat(cells, grid)
hex_globe(grid, values = centres$lat_deg, palette = "Blue-Red 3",
width = "100%", height = 560)The values go to the graphics card as a texture laid out like the grid’s quads, one block per quad, padded with the cells across each quad’s edges, at the grid’s resolution and at every coarser one (Jubair et al. 2016 store icosahedral data in such blocks). Where the cells on screen shrink below a pixel, the fill is read from the coarser grid whose cells are about a pixel wide; its cells hold the mean of the values in them, and are as opaque as the share of them the given cells cover. A fine grid seen whole shows the pattern of its values rather than noise, and a few scattered cells fade rather than flicker.
smooth = TRUE blends the values of neighbouring cells
linearly across the triangles of cell centres, as a field sampled at the
centres.
hex_globe(grid, values = centres$lat_deg, palette = "Blue-Red 3", smooth = TRUE,
width = "100%", height = 560)The solid
surface = "solid" opens on the flat faces of the
icosahedron. Moving the slider to the right folds the faces onto the
sphere.
hex_globe(grid, surface = "solid", center = "pacific", land = FALSE,
width = "100%", height = 560)