Mapbox-gl + d3.geo.tile + clipping

This example shows how to overlay a custom clipped tile layer on top of a Mapbox-gl map. Currently it is not possible to do an arbitrary clip of a mapbox-gl layer, so I'm using d3.geo.tile to overlay raster tiles and clip them using svg clip-paths.

Built with blockbuilder.org

forked from mbostock's block: Clipped Map Tiles

forked from enjalot's block: Mapbox -> d3 projection

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <script src="//d3js.org/topojson.v1.min.js"></script>
  <script src="d3.geo.tile.min.js"></script>
  
  <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.js'></script>
  <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.css' rel='stylesheet' />

circle.mapbox {
      stroke: #111;
      fill-opacity: 0.1;
    }

circle.d3 {
      fill-opacity: 0.1;
      stroke-width: 3;
      stroke: orange;
    }
  </style>
</head>

<body>
  <div id="map"></div>
  <svg id="overlay2"></svg>
  <script>
  
    mapboxgl.accessToken = 'pk.eyJ1IjoiZW5qYWxvdCIsImEiOiJjaWhtdmxhNTIwb25zdHBsejk0NGdhODJhIn0.2-F2hS_oTZenAWc0BMf_uw'
    
    //Setup mapbox-gl map
    var map = new mapboxgl.Map({
      container: 'map', // container id
      style: "mapbox://styles/mapbox/light-v9",
      center: [-96, 38.3],
      zoom: 3,
      
    })
    //map.scrollZoom.disable()
    map.addControl(new mapboxgl.Navigation());

// Setup our svg layer that we can manipulate with d3
    var container = map.getCanvasContainer()
    var svg = d3.select(container).append("svg")

// we can project a lonlat coordinate pair using mapbox's built in projection function
    function mapboxProjection(lonlat) {
      var p = map.project(new mapboxgl.LngLat(lonlat[0], lonlat[1]))
      return [p.x, p.y];
    }

// we calculate the scale given mapbox state (derived from viewport-mercator-project's code)
    // to define a d3 projection
    function getD3() {
      var bbox = document.body.getBoundingClientRect();
      var center = map.getCenter();
      var zoom = map.getZoom();
      // 512 is hardcoded tile size, might need to be 256 or changed to suit your map config
      var scale = (512) * 0.5 / Math.PI * Math.pow(2, zoom);

var d3projection = d3.geo.mercator()
        .center([center.lng, center.lat])
        .translate([bbox.width/2, bbox.height/2])
        .scale(scale);

return d3projection;
    }
    // calculate the original d3 projection
    var d3Projection = getD3();
    
    var tile = d3.geo.tile()
    .scale(d3Projection.scale() * 2 * Math.PI)
    .translate(d3Projection([0, 0]))
    .zoomDelta((window.devicePixelRatio || 1) - .5);
    
    
    // we want to render the same point
    var point = [-96, 38.3]
  
    var mapboxCircle = svg.append("circle").classed("mapbox", true)
    var d3Circle = svg.append("circle").classed("d3", true)

var path = d3.geo.path()
      .projection(d3Projection)
    
    var clipped = svg.append("g")
      .attr("clip-path", "url(#clip)")
    
    d3.json("https://gist.githubusercontent.com/mbostock/4090846/raw/d534aba169207548a8a3d670c9c2cc719ff05c47/us.json", function(error, topology) {
      if (error) throw error;

var defs = svg.append("defs");

defs.append("path")
        .attr("id", "land")
        .datum(topojson.feature(topology, topology.objects.land))
        .attr("d", path);

defs.append("clipPath")
        .attr("id", "clip")
        .append("use")
          .attr("xlink:href", "#land");
    
      render();
    })

function render() {
      var bbox = document.body.getBoundingClientRect();
      // we update our calculated projections whenever the underlying map changes 
      // due to zoom and pan
      d3Projection = getD3();
      // update our tile generator
      tile.scale(d3Projection.scale() * 2 * Math.PI)
        .translate(d3Projection([0, 0]))
        .size([bbox.width, bbox.height])
      
      path.projection(d3Projection)
      
      d3.select("#land").attr("d", path)

mapboxCircle.attr({
        cx: mapboxProjection(point)[0],
        cy: mapboxProjection(point)[1],
        r: 15// * currentScale
      })

d3Circle.attr({
        cx: d3Projection(point)[0],
        cy: d3Projection(point)[1],
        r: 25// * currentScale
      })
      
      var tiles = tile();
      var tiled = clipped.selectAll("image")
        .data(tiles, function(d) { return d[2] + "/" + d[0] + "/" + d[1] })
      tiled.exit().remove();
      tiled.enter().append("image")
        .attr("xlink:href", function(d) { 
          var random = ["a", "b", "c", "d"][Math.random() * 4 | 0];
        	return "https://" + "a" + ".tiles.mapbox.com/v3/mapbox.natural-earth-2/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; 
      	})
      tiled
        .attr("width", Math.round(tiles.scale))
        .attr("height", Math.round(tiles.scale))
        .attr("x", function(d) { return Math.round((d[0] + tiles.translate[0]) * tiles.scale); })
        .attr("y", function(d) { return Math.round((d[1] + tiles.translate[1]) * tiles.scale); });
      
    }

// re-render our visualization whenever the view changes
    map.on("viewreset", function() {
      render()
    })
    map.on("move", function() {
      render()
    })

// render our initial visualization
    render()

</script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js

https://d3js.org/topojson.v1.min.js

https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.js