add bridge rendering

src/constants/color.js

@@ -1,6 +1,8 @@
 export const backgroundFill = `hsl(30, 44%, 96%)`;
 export const backgroundFillTranslucent = `hsla(30, 44%, 96%, 0.8)`;
 
+export const bridgeFill = "hsl(0, 20%, 80%)";
+
 export const waterFill = "hsl(211, 50%, 85%)";
 export const waterFillTranslucent = "hsla(211, 50%, 85%, 0.5)";
 export const waterIntermittentFill = "hsla(211, 60%, 85%, 0.3)";

src/js/util.js

@@ -38,3 +38,35 @@ export function zoomMultiply(arr, multiplier) {
   }
   return transformedArray;
 }
+
+//Create a zoom interpolation expression, given width at zoom 20
+export function zoomInterpolate(widthZ20) {
+  return [
+    "interpolate",
+    ["exponential", 1.2],
+    ["zoom"],
+    8,
+    multiplyMatchExpression(widthZ20, 1 / 16),
+    12,
+    multiplyMatchExpression(widthZ20, 1 / 4),
+    20,
+    widthZ20,
+  ];
+}
+
+export function multiplyMatchExpression(value, factor) {
+  if (Array.isArray(value)) {
+    var result = [value[0], value[1]];
+    for (let i = 2; i < value.length - 1; i++) {
+      if (i % 2 == 0) {
+        result.push(value[i]);
+      } else {
+        result.push(multiplyMatchExpression(value[i], factor));
+      }
+    }
+    result.push(multiplyMatchExpression(value[value.length - 1], factor));
+    return result;
+  } else {
+    return value * factor;
+  }
+}

src/layer/bridge.js

@@ -0,0 +1,123 @@
+"use strict";
+
+import * as Color from "../constants/color.js";
+import * as Util from "../js/util.js";
+
+// Bridge areas
+export const bridge = {
+  type: "fill-extrusion",
+  source: "openmaptiles",
+  "source-layer": "transportation",
+  id: "bridge",
+  minzoom: 13,
+  layout: {
+    visibility: "visible",
+  },
+  paint: {
+    "fill-extrusion-color": Color.bridgeFill,
+    "fill-extrusion-height": ["+", 3, ["coalesce", ["get", "layer"], 0]],
+    "fill-extrusion-opacity": 0.6,
+  },
+  filter: ["all", ["==", ["get", "class"], "bridge"]],
+};
+
+// Bridge casing for highways and railways
+export const bridgeCasing = {
+  type: "line",
+  source: "openmaptiles",
+  "source-layer": "transportation",
+  id: "bridge_casing",
+  minzoom: 13,
+  layout: {
+    "line-cap": "butt",
+    "line-join": "bevel",
+    visibility: "visible",
+  },
+  paint: {
+    "line-color": Color.bridgeFill,
+    "line-opacity": 0.8,
+    "line-width": Util.zoomInterpolate([
+      "match",
+      ["get", "class"],
+      ["rail", "transit"],
+      ["match", ["get", "service"], ["siding", "spur", "yard"], 10, 14],
+      "motorway",
+      ["match", ["get", "ramp"], 1, 18, 28],
+      "trunk",
+      [
+        "match",
+        ["get", "expressway"],
+        1,
+        34,
+        ["match", ["get", "ramp"], 1, 16, 28],
+      ],
+      "primary",
+      [
+        "match",
+        ["get", "expressway"],
+        1,
+        32,
+        ["match", ["get", "ramp"], 1, 15, 24],
+      ],
+      "secondary",
+      [
+        "match",
+        ["get", "expressway"],
+        1,
+        26,
+        ["match", ["get", "ramp"], 1, 14, 20],
+      ],
+      ["tertiary", "busway", "bus_guideway"],
+      [
+        "match",
+        ["get", "expressway"],
+        1,
+        20,
+        ["match", ["get", "ramp"], 1, 13, 18],
+      ],
+      "minor",
+      14,
+      "service",
+      [
+        "match",
+        ["get", "service"],
+        ["alley", "driveway", "drive-through", "parking_aisle"],
+        9,
+        11,
+      ],
+      20,
+    ]),
+  },
+  filter: [
+    "all",
+    ["==", ["get", "brunnel"], "bridge"],
+    [
+      "in",
+      ["get", "class"],
+      [
+        "literal",
+        [
+          "motorway",
+          "trunk",
+          "primary",
+          "secondary",
+          "tertiary",
+          "busway",
+          "bus_guideway",
+          "minor",
+          "service",
+          "rail",
+          "transit",
+        ],
+      ],
+    ],
+  ],
+};
+
+export const legendEntries = [
+  {
+    description: "Bridge",
+    layers: [bridge.id],
+    filter: ["==", ["get", "class"], "bridge"],
+  },
+];

src/layer/index.js

@@ -6,6 +6,7 @@ import * as lyrAerialway from "./aerialway.js";
 import * as lyrAeroway from "./aeroway.js";
 import * as lyrBackground from "./background.js";
 import * as lyrBoundary from "./boundary.js";
+import * as lyrBridge from "./bridge.js";
 import * as lyrConstruction from "./construction.js";
 import * as lyrHighwayShield from "./highway_shield.js";
 import * as lyrLanduse from "./landuse.js";
@@ -143,7 +144,8 @@ export function build(locales) {
   layers.push(lyrBuilding.building);
 
   var bridgeLayers = [
-    lyrRail.bridgeCasing,
+    lyrBridge.bridge,
+    lyrBridge.bridgeCasing,
 
     lyrRoad.trunkLinkBridge.casing(),
     lyrRoad.motorwayLinkBridge.casing(),

src/layer/rail.js

@@ -6,38 +6,6 @@ import * as Util from "../js/util.js";
 // Exponent base for inter-zoom interpolation
 let railExp = 1.2;
 
-// Helper functions to create zoom interpolation expressions
-function multiplyMatchExpression(value, factor) {
-  if (Array.isArray(value)) {
-    var result = [value[0], value[1]];
-    for (let i = 2; i < value.length - 1; i++) {
-      if (i % 2 == 0) {
-        result.push(value[i]);
-      } else {
-        result.push(multiplyMatchExpression(value[i], factor));
-      }
-    }
-    result.push(multiplyMatchExpression(value[value.length - 1], factor));
-    return result;
-  } else {
-    return value * factor;
-  }
-}
-
-function zoomInterpolate(widthZ20) {
-  return [
-    "interpolate",
-    ["exponential", railExp],
-    ["zoom"],
-    8,
-    multiplyMatchExpression(widthZ20, 1 / 16),
-    12,
-    multiplyMatchExpression(widthZ20, 1 / 4),
-    20,
-    widthZ20,
-  ];
-}
-
 // Helper function to create a "filter" block for a particular railway class.
 function filterRail(brunnel) {
   return [
@@ -103,28 +71,6 @@ var opacity = [
   1,
 ];
 
-// Bridge casing layers
-export const bridgeCasing = {
-  ...defRail,
-  id: "rail_bridge-casing",
-  filter: [
-    "all",
-    ["==", ["get", "brunnel"], "bridge"],
-    ["in", ["get", "class"], ["literal", ["rail", "transit"]]],
-  ],
-  minzoom: 13,
-  layout: {
-    "line-cap": "butt",
-    "line-join": "bevel",
-    visibility: "visible",
-  },
-  paint: {
-    "line-color": Color.backgroundFill,
-    "line-opacity": opacity,
-    "line-width": zoomInterpolate([...serviceSelector, 4, 6]),
-  },
-};
-
 // Generate a unique layer ID
 function uniqueLayerID(part, brunnel, constraints) {
   var layerID = ["rail", part, brunnel].join("_");
@@ -168,7 +114,7 @@ class Railway {
     layer.paint = {
       "line-color": lineColor,
       "line-opacity": opacity,
-      "line-width": zoomInterpolate(lineWidth),
+      "line-width": Util.zoomInterpolate(lineWidth),
     };
     if (this.constraints != null) {
       layer.filter.push(this.constraints);
@@ -191,8 +137,8 @@ class Railway {
     layer.paint = {
       "line-color": lineColor,
       "line-opacity": opacity,
-      "line-width": zoomInterpolate(
-        multiplyMatchExpression(lineWidth, this.dashWidthFactor)
+      "line-width": Util.zoomInterpolate(
+        Util.multiplyMatchExpression(lineWidth, this.dashWidthFactor)
       ),
       "line-dasharray": this.dashArray.map(
         (stop) => stop / 2 / this.dashWidthFactor