% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/ddbs_mvt.R
\name{ddbs_as_mvt_geom}
\alias{ddbs_as_mvt_geom}
\title{Transform geometries into Mapbox Vector Tile coordinate space}
\usage{
ddbs_as_mvt_geom(
  x,
  bounds,
  extent = 4096L,
  buffer = 256L,
  clip_geom = TRUE,
  conn = NULL,
  name = NULL,
  mode = NULL,
  overwrite = FALSE,
  quiet = FALSE
)
}
\arguments{
\item{x}{Input spatial data. Can be:
\itemize{
\item A \code{duckspatial_df} object (lazy spatial data frame via dbplyr)
\item An \code{sf} object
\item A \code{tbl_lazy} from dbplyr
\item A character string naming a table/view in \code{conn}
}
Data is returned from this object.}

\item{bounds}{The tile bounding box, in the same CRS as \code{x}. Either a
numeric vector \code{c(xmin, ymin, xmax, ymax)} or an object understood by
\code{sf::st_bbox()} (e.g. an \code{sf}, \code{sfc}, or \code{bbox}
object).}

\item{extent}{Integer. The width and height of the tile coordinate space
(the geometry is mapped into the square \code{[0, extent]}). Defaults to
\code{4096}.}

\item{buffer}{Integer. The number of pixels by which the tile bounds are
expanded before clipping, to avoid rendering artefacts at tile edges.
Defaults to \code{256}.}

\item{clip_geom}{Logical. If \code{TRUE} (default), geometries are clipped to
the (buffered) tile bounds; geometries falling entirely outside become
\code{NULL}. If \code{FALSE}, geometries are transformed but not clipped.}

\item{conn}{A connection object to a DuckDB database. If \code{NULL}, the function
runs on a temporary DuckDB database.}

\item{name}{A character string of length one specifying the name of the table,
or a character string of length two specifying the schema and table
names. If \code{NULL} (the default), the function returns the result as an
\code{sf} object}

\item{mode}{Character. Controls the return type. Options:
\itemize{
\item \code{"duckspatial"} (default): Lazy spatial data frame backed by dbplyr/DuckDB
\item \code{"sf"}: Eagerly collected sf object (uses memory)
}
Can be set globally via \code{\link{ddbs_options}(mode = "...")} or
per-function via this argument. Per-function overrides global setting.}

\item{overwrite}{Boolean. whether to overwrite the existing table if it exists. Defaults
to \code{FALSE}. This argument is ignored when \code{name} is \code{NULL}.}

\item{quiet}{A logical value. If \code{TRUE}, suppresses any informational messages.
Defaults to \code{FALSE}.}
}
\value{
Depends on the \code{mode} argument (or global preference set by \code{\link{ddbs_options}}):
\itemize{
\item \code{duckspatial} (default): A \code{duckspatial_df} (lazy spatial data frame) backed by dbplyr/DuckDB.
\item \code{sf}: An eagerly collected object in R memory, that will return the same data type as the
\code{sf} equivalent (e.g. \code{sf} or \code{units} vector).
}
When \code{name} is provided, the result is also written as a table or view in DuckDB and the function returns \code{TRUE} (invisibly).
}
\description{
Prepares geometries for encoding as Mapbox Vector Tiles (MVT) by clipping
them to a tile's bounding box and transforming the coordinates into the
tile's integer pixel space. This is a low-level building block; to produce a
ready-to-serve tile pyramid use \code{\link{ddbs_write_mbtiles}}.
}
\details{
This is a wrapper around DuckDB's \code{ST_AsMVTGeom}. The output geometries
use the MVT tile coordinate system: the origin is the top-left corner and the
y-axis points downwards, so the result is no longer in the input CRS (the CRS
is dropped). Geometries that fall completely outside the tile bounds return
\code{NULL} when \code{clip_geom = TRUE}.
}
\examples{
\dontrun{
library(duckspatial)

argentina_ddbs <- ddbs_open_dataset(
  system.file("spatial/argentina.geojson", package = "duckspatial")
)

## use the layer's own bounding box as the tile bounds
ddbs_as_mvt_geom(argentina_ddbs, bounds = sf::st_bbox(sf::st_as_sf(argentina_ddbs)))

## explicit numeric bounds and a smaller tile extent
ddbs_as_mvt_geom(
  argentina_ddbs,
  bounds = c(-74, -56, -53, -21),
  extent = 256
)
}
}
