preliminary 3D feature reading

README.md

@@ -79,6 +79,7 @@ An object that contains the data for a single vector tile layer.
 - **name** (`String) `— layer name
 - **extent** (`Number`, default: `4096`) — tile extent size
 - **length** (`Number`) — number of features in the layer
+- **dimensions** (`Number`, default: `2`) — number of dimensions in the layer
 
 #### Methods
 
@@ -99,6 +100,7 @@ An object that contains the data for a single feature.
 #### Methods
 
 - **loadGeometry()** — parses feature geometry and returns an array of
-  [Point](https://github.com/mapbox/point-geometry) arrays (with each point having `x` and `y` properties)
-- **bbox()** — calculates and returns the bounding box of the feature in the form `[x1, y1, x2, y2]`
+  [Point](https://github.com/mapbox/point-geometry) arrays (with each point having `x` and `y` properties,
+  and `z` properties if the layer's `dimension` property is set to `3`)
+- **bbox()** — calculates and returns the bounding box of the feature in the form `[x1, y1, x2, y2, z1?, z2?]`
 - **toGeoJSON(x, y, z)** — returns a GeoJSON representation of the feature. (`x`, `y`, and `z` refer to the containing tile's index.)

fixtures.js

@@ -2,6 +2,8 @@ var mapnik = require('mapnik');
 var path = require('path');
 var fs = require('fs');
 
+// TODO since node-mapnik will not support vt3 (?), this won't work to generate vt3 fixtures
+
 mapnik.register_datasource(path.join(mapnik.settings.paths.input_plugins, 'geojson.input'));
 
 var fixtures = {

lib/vectortilefeature.js

@@ -4,10 +4,11 @@ var Point = require('@mapbox/point-geometry');
 
 module.exports = VectorTileFeature;
 
-function VectorTileFeature(pbf, end, extent, keys, values) {
+function VectorTileFeature(pbf, end, extent, dimensions, keys, values) {
     // Public
     this.properties = {};
     this.extent = extent;
+    this.dimensions = dimensions;
     this.type = 0;
 
     // Private
@@ -47,6 +48,7 @@ VectorTileFeature.prototype.loadGeometry = function() {
         length = 0,
         x = 0,
         y = 0,
+        z = 0,
         lines = [],
         line;
 
@@ -63,12 +65,15 @@ VectorTileFeature.prototype.loadGeometry = function() {
             x += pbf.readSVarint();
             y += pbf.readSVarint();
 
+            if (this.dimensions === 3) z += pbf.readSVarint();
+
             if (cmd === 1) { // moveTo
                 if (line) lines.push(line);
                 line = [];
             }
 
-            line.push(new Point(x, y));
+            if (this.dimensions === 2) line.push(new Point(x, y));
+            else if (this.dimensions === 3) line.push(new Point(x, y, z));
 
         } else if (cmd === 7) {
 
@@ -99,7 +104,9 @@ VectorTileFeature.prototype.bbox = function() {
         x1 = Infinity,
         x2 = -Infinity,
         y1 = Infinity,
-        y2 = -Infinity;
+        y2 = -Infinity,
+        z1 = Infinity,
+        z2 = -Infinity;
 
     while (pbf.pos < end) {
         if (length <= 0) {
@@ -118,24 +125,33 @@ VectorTileFeature.prototype.bbox = function() {
             if (y < y1) y1 = y;
             if (y > y2) y2 = y;
 
+            if (this.dimensions === 3) {
+                z += pbf.readSVarint();
+                if (z < z1) z1 = z;
+                if (z > z2) z2 = z;
+            }
+
         } else if (cmd !== 7) {
             throw new Error('unknown command ' + cmd);
         }
     }
 
-    return [x1, y1, x2, y2];
+    if (this.dimensions === 2) return [x1, y1, x2, y2];
+    else if (this.dimensions === 3) return [x1, y1, x2, y2, z1, z2];
 };
 
 VectorTileFeature.prototype.toGeoJSON = function(x, y, z) {
     var size = this.extent * Math.pow(2, z),
         x0 = this.extent * x,
         y0 = this.extent * y,
+        z0 = this.extent * z,
         coords = this.loadGeometry(),
         type = VectorTileFeature.types[this.type],
         i, j;
 
     function project(line) {
         for (var j = 0; j < line.length; j++) {
+            // TODO project z coord
             var p = line[j], y2 = 180 - (p.y + y0) * 360 / size;
             line[j] = [
                 (p.x + x0) * 360 / size - 180,
@@ -161,6 +177,7 @@ VectorTileFeature.prototype.toGeoJSON = function(x, y, z) {
         break;
 
     case 3:
+        // TODO polygons w 3 dimensions should be against spec rules, but should that be enforced here? in creation? ???
         coords = classifyRings(coords);
         for (i = 0; i < coords.length; i++) {
             for (j = 0; j < coords[i].length; j++) {

lib/vectortilelayer.js

@@ -10,6 +10,7 @@ function VectorTileLayer(pbf, end) {
     this.name = null;
     this.extent = 4096;
     this.length = 0;
+    this.dimensions = 2;
 
     // Private
     this._pbf = pbf;
@@ -29,6 +30,7 @@ function readLayer(tag, layer, pbf) {
     else if (tag === 2) layer._features.push(pbf.pos);
     else if (tag === 3) layer._keys.push(pbf.readString());
     else if (tag === 4) layer._values.push(readValueMessage(pbf));
+    else if (tag === 6) layer.dimensions = pbf.readVarint();
 }
 
 function readValueMessage(pbf) {
@@ -57,5 +59,5 @@ VectorTileLayer.prototype.feature = function(i) {
     this._pbf.pos = this._features[i];
 
     var end = this._pbf.readVarint() + this._pbf.pos;
-    return new VectorTileFeature(this._pbf, end, this.extent, this._keys, this._values);
+    return new VectorTileFeature(this._pbf, end, this.extent, this.dimensions, this._keys, this._values);
 };

proto/vector_tile.proto

@@ -37,10 +37,11 @@ message tile {
         // Contains a stream of commands and parameters (vertices). The
         // repeat count is shifted to the left by 3 bits. This means
         // that the command has 3 bits (0-7). The repeat count
-        // indicates how often this command is to be repeated. Defined
-        // commands are:
-        // - MoveTo:    1   (2 parameters follow)
-        // - LineTo:    2   (2 parameters follow)
+        // indicates how often this command is to be repeated. MoveTo and LineTo
+        // commands should be followed by 2 parameters unless `dimensions` is set
+        // on the enclosing layer to 3. Defined commands are:
+        // - MoveTo:    1   (2-3 parameters follow)
+        // - LineTo:    2   (2-3 parameters follow)
         // - ClosePath: 7   (no parameters follow)
         //
         // Ex.: MoveTo(3, 6), LineTo(8, 12), LineTo(20, 34), ClosePath
@@ -54,7 +55,7 @@ message tile {
         // Commands are encoded as uint32 varints, vertex parameters are
         // encoded as sint32 varints (zigzag). Vertex parameters are
         // also encoded as deltas to the previous position. The original
-        // position is (0,0)
+        // position is (0,0) (or (0, 0, 0) in 3 dimensions)
         repeated uint32 geometry = 4 [ packed = true ];
     }
 
@@ -79,6 +80,9 @@ message tile {
         // The bounding box in this tile spans from 0..4095 units
         optional uint32 extent = 5 [ default = 4096 ];
 
+        // TODO update with official proto file when finalized
+        optional uint32 dimensions = 6 [ default = 2 ];
+
         extensions 16 to max;
     }