Makes the edge lines of
make_waterlines(heightmap, waterdepth = 0, linecolor = "grey40",
zscale = 1, alpha = 1, lwd = 2)A two-dimensional matrix, where each entry in the matrix is the elevation at that point. All points are assumed to be evenly spaced.
Default `0`.
Default `grey40`.
Default `1`. The ratio between the x and y spacing (which are assumed to be equal) and the z axis. For example, if the elevation levels are in units of 1 meter and the grid values are separated by 10 meters, `zscale` would be 10.
Default `1`. Transparency of lines.
Default `2`. Water line width.