unifir (version 0.2.4)

associate_coordinates: Associate vector coordinates with a raster surface for Unity import

Description

Unity uses a left-handed coordinate system, which is effectively "flipped" from our normal way of thinking about spatial coordinate systems. It also can only import terrain as square tiles of side 2^x + 1, for x between 5 and 12. As a result, importing objects into a Unity scene so that they align with terrain surfaces is trickier than you'd expect. This function "associates" the XY coordinates from some sf object, likely a point data set, with some raster object.

Usage

associate_coordinates(object, raster, side_length = 4097)

Value

A data.frame with two columns, X and Y, representing the re-aligned coordinates. If object is point data (or anything object that sf::st_coordinates returns a single row for each row of), these rows will be in the same order as object (and so can be appended via cbind).

Arguments

object

The sf object to take coordinates from. The object will be reprojected (via sf::st_transform) to align with raster.

raster

A raster or file path to a raster to associate coordinates with. Note that different rasters will produce different coordinate outputs; you should run this function with the same raster you plan on bringing into Unity. Any file or object that can be read via terra::rast can be used.

side_length

The side length of terrain tiles, in map units, you intend to bring into Unity. Must be a value equal to 2^x + 1, for x between 5 and 12. All functions in the unifir family default to 4097.

Examples

if (FALSE) {
if (!isTRUE(as.logical(Sys.getenv("CI")))) {
  simulated_data <- data.frame(
    id = seq(1, 100, 1),
    lat = runif(100, 44.04905, 44.17609),
    lng = runif(100, -74.01188, -73.83493)
  )
  simulated_data <- sf::st_as_sf(
    simulated_data,
    coords = c("lng", "lat"),
    crs = 4326
   )
  output_files <- terrainr::get_tiles(simulated_data)
  temptiff <- tempfile(fileext = ".tif")
  terrainr::merge_rasters(output_files["elevation"][[1]], temptiff)
  associate_coordinates(simulated_data, temptiff)
}
}