Decouple source and rendered tile grid of vector tile sources

2017-05-08 17:19:55 +02:00
parent 2486b25e5e
commit 785e7135a7
18 changed files with 620 additions and 287 deletions
--- a/examples/mapbox-vector-tiles-advanced.html
+++ b/examples/mapbox-vector-tiles-advanced.html
@@ -3,7 +3,7 @@ layout: example.html
 title: Advanced Mapbox Vector Tiles
 shortdesc: Example of a Mapbox vector tiles map with custom tile grid.
 docs: >
-  A vector tiles map which reuses the same tiles for subsequent zoom levels to save bandwidth on mobile devices. **Note**: No map will be visible when the access token has expired.
+  A vector tiles map which reuses the same source tiles for subsequent zoom levels to save bandwidth on mobile devices. **Note**: No map will be visible when the access token has expired.
 tags: "mapbox, vector, tiles, mobile"
 resources:
  - resources/mapbox-streets-v6-style.js
--- a/examples/mapbox-vector-tiles-advanced.js
+++ b/examples/mapbox-vector-tiles-advanced.js
@@ -15,25 +15,16 @@ goog.require('ol.tilegrid.TileGrid');

 var key = 'pk.eyJ1IjoiYWhvY2V2YXIiLCJhIjoiRk1kMWZaSSJ9.E5BkluenyWQMsBLsuByrmg';

-// For how many zoom levels do we want to use the same vector tiles?
-// 1 means "use tiles from all zoom levels". 2 means "use the same tiles for 2
-// subsequent zoom levels".
-var reuseZoomLevels = 2;
-
-// Offset of loaded tiles from web mercator zoom level 0.
-// 0 means "At map zoom level 0, use tiles from zoom level 0". 1 means "At map
-// zoom level 0, use tiles from zoom level 1".
-var zoomOffset = 1;
-
-// Calculation of tile urls
+// Calculation of resolutions that match zoom levels 1, 3, 5, 7, 9, 11, 13, 15.
 var resolutions = [];
-for (var z = zoomOffset / reuseZoomLevels; z <= 22 / reuseZoomLevels; ++z) {
-  resolutions.push(156543.03392804097 / Math.pow(2, z * reuseZoomLevels));
+for (var i = 0; i <= 7; ++i) {
+  resolutions.push(156543.03392804097 / Math.pow(2, i * 2));
 }
+// Calculation of tile urls for zoom levels 1, 3, 5, 7, 9, 11, 13, 15.
 function tileUrlFunction(tileCoord) {
  return ('https://{a-d}.tiles.mapbox.com/v4/mapbox.mapbox-streets-v6/' +
      '{z}/{x}/{y}.vector.pbf?access_token=' + key)
-      .replace('{z}', String(tileCoord[0] * reuseZoomLevels + zoomOffset))
+      .replace('{z}', String(tileCoord[0] * 2 - 1))
      .replace('{x}', String(tileCoord[1]))
      .replace('{y}', String(-tileCoord[2] - 1))
      .replace('{a-d}', 'abcd'.substr(
@@ -43,8 +34,6 @@ function tileUrlFunction(tileCoord) {
 var map = new ol.Map({
  layers: [
    new ol.layer.VectorTile({
-      renderMode: 'vector',
-      preload: Infinity,
      source: new ol.source.VectorTile({
        attributions: '© <a href="https://www.mapbox.com/map-feedback/">Mapbox</a> ' +
          '© <a href="https://www.openstreetmap.org/copyright">' +
@@ -52,9 +41,10 @@ var map = new ol.Map({
        format: new ol.format.MVT(),
        tileGrid: new ol.tilegrid.TileGrid({
          extent: ol.proj.get('EPSG:3857').getExtent(),
-          resolutions: resolutions
+          resolutions: resolutions,
+          tileSize: 512
        }),
-        tilePixelRatio: 16,
+        tilePixelRatio: 8,
        tileUrlFunction: tileUrlFunction
      }),
      style: createMapboxStreetsV6Style()
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -4864,7 +4864,7 @@ olx.source.VectorTileOptions.prototype.state;


 /**
- * Class used to instantiate image tiles. Default is {@link ol.VectorTile}.
+ * Class used to instantiate vector tiles. Default is {@link ol.VectorTile}.
 * @type {function(new: ol.VectorTile, ol.TileCoord,
 *                 ol.TileState, string, ol.format.Feature,
 *                 ol.TileLoadFunctionType)|undefined}
--- a/src/ol/imagetile.js
+++ b/src/ol/imagetile.js
@@ -70,8 +70,8 @@ ol.ImageTile.prototype.disposeInternal = function() {


 /**
- * Get the image element for this tile.
- * @inheritDoc
+ * Get the HTML image element for this tile (may be a Canvas, Image, or Video).
+ * @return {HTMLCanvasElement|HTMLImageElement|HTMLVideoElement} Image.
 * @api
 */
 ol.ImageTile.prototype.getImage = function() {
--- a/src/ol/renderer/canvas/vectortilelayer.js
+++ b/src/ol/renderer/canvas/vectortilelayer.js
@@ -1,6 +1,7 @@
 goog.provide('ol.renderer.canvas.VectorTileLayer');

 goog.require('ol');
+goog.require('ol.TileState');
 goog.require('ol.dom');
 goog.require('ol.extent');
 goog.require('ol.proj');
@@ -12,7 +13,6 @@ goog.require('ol.render.canvas.ReplayGroup');
 goog.require('ol.render.replay');
 goog.require('ol.renderer.canvas.TileLayer');
 goog.require('ol.renderer.vector');
-goog.require('ol.size');
 goog.require('ol.transform');


@@ -23,6 +23,9 @@ goog.require('ol.transform');
 */
 ol.renderer.canvas.VectorTileLayer = function(layer) {

+  /**
+   * @type {CanvasRenderingContext2D}
+   */
  this.context = null;

  ol.renderer.canvas.TileLayer.call(this, layer);
@@ -95,12 +98,12 @@ ol.renderer.canvas.VectorTileLayer.prototype.prepareFrame = function(frameState,


 /**
- * @param {ol.VectorTile} tile Tile.
+ * @param {ol.VectorImageTile} tile Tile.
 * @param {olx.FrameState} frameState Frame state.
 * @private
 */
-ol.renderer.canvas.VectorTileLayer.prototype.createReplayGroup_ = function(tile,
-    frameState) {
+ol.renderer.canvas.VectorTileLayer.prototype.createReplayGroup_ = function(
+    tile, frameState) {
  var layer = this.getLayer();
  var pixelRatio = frameState.pixelRatio;
  var projection = frameState.viewState.projection;
@@ -113,78 +116,89 @@ ol.renderer.canvas.VectorTileLayer.prototype.createReplayGroup_ = function(tile,
    return;
  }

-  replayState.replayGroup = null;
-  replayState.dirty = false;
+  var sourceTiles = tile.getSourceTiles();
+  for (var t = 0, tt = sourceTiles.length; t < tt; ++t) {
+    var sourceTile = sourceTiles[t];
+    sourceTile.replayGroup = null;
+    replayState.dirty = false;

-  var source = /** @type {ol.source.VectorTile} */ (layer.getSource());
-  var tileGrid = source.getTileGrid();
-  var tileCoord = tile.tileCoord;
-  var tileProjection = tile.getProjection();
-  var resolution = tileGrid.getResolution(tileCoord[0]);
-  var extent, reproject, tileResolution;
-  if (tileProjection.getUnits() == ol.proj.Units.TILE_PIXELS) {
-    var tilePixelRatio = tileResolution = source.getTilePixelRatio();
-    var tileSize = ol.size.toSize(tileGrid.getTileSize(tileCoord[0]));
-    extent = [0, 0, tileSize[0] * tilePixelRatio, tileSize[1] * tilePixelRatio];
-  } else {
-    tileResolution = resolution;
-    extent = tileGrid.getTileCoordExtent(tileCoord);
-    if (!ol.proj.equivalent(projection, tileProjection)) {
-      reproject = true;
-      tile.setProjection(projection);
-    }
-  }
-  replayState.dirty = false;
-  var replayGroup = new ol.render.canvas.ReplayGroup(0, extent,
-      tileResolution, source.getOverlaps(), layer.getRenderBuffer());
-  var squaredTolerance = ol.renderer.vector.getSquaredTolerance(
-      tileResolution, pixelRatio);
-
-  /**
-   * @param {ol.Feature|ol.render.Feature} feature Feature.
-   * @this {ol.renderer.canvas.VectorTileLayer}
-   */
-  function renderFeature(feature) {
-    var styles;
-    var styleFunction = feature.getStyleFunction();
-    if (styleFunction) {
-      styles = styleFunction.call(/** @type {ol.Feature} */ (feature), resolution);
+    var source = /** @type {ol.source.VectorTile} */ (layer.getSource());
+    var sourceTileGrid = source.getTileGrid();
+    var sourceTileCoord = sourceTile.tileCoord;
+    var tileProjection = sourceTile.getProjection();
+    var tileGrid = source.getTileGridForProjection(projection);
+    var resolution = tileGrid.getResolution(tile.tileCoord[0]);
+    var sourceTileResolution = sourceTileGrid.getResolution(sourceTile.tileCoord[0]);
+    var tileExtent = tileGrid.getTileCoordExtent(tile.wrappedTileCoord);
+    var sourceTileExtent = sourceTileGrid.getTileCoordExtent(sourceTileCoord);
+    var sharedExtent = ol.extent.getIntersection(tileExtent, sourceTileExtent);
+    var extent, reproject, tileResolution;
+    if (tileProjection.getUnits() == ol.proj.Units.TILE_PIXELS) {
+      var tilePixelRatio = tileResolution = source.getTilePixelRatio();
+      var transform = ol.transform.compose(this.tmpTransform_,
+          0, 0,
+          1 / sourceTileResolution * tilePixelRatio, -1 / sourceTileResolution * tilePixelRatio,
+          0,
+          -sourceTileExtent[0], -sourceTileExtent[3]);
+      extent = (ol.transform.apply(transform, [sharedExtent[0], sharedExtent[3]])
+          .concat(ol.transform.apply(transform, [sharedExtent[2], sharedExtent[1]])));
    } else {
-      styleFunction = layer.getStyleFunction();
+      tileResolution = resolution;
+      extent = sharedExtent;
+      if (!ol.proj.equivalent(projection, tileProjection)) {
+        reproject = true;
+        sourceTile.setProjection(projection);
+      }
+    }
+    replayState.dirty = false;
+    var replayGroup = new ol.render.canvas.ReplayGroup(0, extent,
+        tileResolution, source.getOverlaps(), layer.getRenderBuffer());
+    var squaredTolerance = ol.renderer.vector.getSquaredTolerance(
+        tileResolution, pixelRatio);
+
+    /**
+     * @param {ol.Feature|ol.render.Feature} feature Feature.
+     * @this {ol.renderer.canvas.VectorTileLayer}
+     */
+    var renderFeature = function(feature) {
+      var styles;
+      var styleFunction = feature.getStyleFunction();
      if (styleFunction) {
-        styles = styleFunction(feature, resolution);
+        styles = styleFunction.call(/** @type {ol.Feature} */ (feature), resolution);
+      } else {
+        styleFunction = layer.getStyleFunction();
+        if (styleFunction) {
+          styles = styleFunction(feature, resolution);
+        }
      }
-    }
-    if (styles) {
-      if (!Array.isArray(styles)) {
-        styles = [styles];
+      if (styles) {
+        if (!Array.isArray(styles)) {
+          styles = [styles];
+        }
+        var dirty = this.renderFeature(feature, squaredTolerance, styles,
+            replayGroup);
+        this.dirty_ = this.dirty_ || dirty;
+        replayState.dirty = replayState.dirty || dirty;
      }
-      var dirty = this.renderFeature(feature, squaredTolerance, styles,
-          replayGroup);
-      this.dirty_ = this.dirty_ || dirty;
-      replayState.dirty = replayState.dirty || dirty;
+    };
+
+    var features = sourceTile.getFeatures();
+    if (renderOrder && renderOrder !== replayState.renderedRenderOrder) {
+      features.sort(renderOrder);
    }
-  }
-
-  var features = tile.getFeatures();
-  if (renderOrder && renderOrder !== replayState.renderedRenderOrder) {
-    features.sort(renderOrder);
-  }
-  var feature;
-  for (var i = 0, ii = features.length; i < ii; ++i) {
-    feature = features[i];
-    if (reproject) {
-      feature.getGeometry().transform(tileProjection, projection);
+    var feature;
+    for (var i = 0, ii = features.length; i < ii; ++i) {
+      feature = features[i];
+      if (reproject) {
+        feature.getGeometry().transform(tileProjection, projection);
+      }
+      renderFeature.call(this, feature);
    }
-    renderFeature.call(this, feature);
+    replayGroup.finish();
+    sourceTile.setReplayGroup(tile.tileCoord.toString(), replayGroup);
  }
-
-  replayGroup.finish();
-
  replayState.renderedRevision = revision;
  replayState.renderedRenderOrder = renderOrder;
-  replayState.replayGroup = replayGroup;
-  replayState.resolution = NaN;
 };


@@ -193,10 +207,10 @@ ol.renderer.canvas.VectorTileLayer.prototype.createReplayGroup_ = function(tile,
 */
 ol.renderer.canvas.VectorTileLayer.prototype.drawTileImage = function(
    tile, frameState, layerState, x, y, w, h, gutter) {
-  var vectorTile = /** @type {ol.VectorTile} */ (tile);
-  this.createReplayGroup_(vectorTile, frameState);
+  var vectorImageTile = /** @type {ol.VectorImageTile} */ (tile);
+  this.createReplayGroup_(vectorImageTile, frameState);
  if (this.context) {
-    this.renderTileImage_(vectorTile, frameState, layerState);
+    this.renderTileImage_(vectorImageTile, frameState, layerState);
    ol.renderer.canvas.TileLayer.prototype.drawTileImage.apply(this, arguments);
  }
 };
@@ -213,54 +227,62 @@ ol.renderer.canvas.VectorTileLayer.prototype.forEachFeatureAtCoordinate = functi
  /** @type {Object.<string, boolean>} */
  var features = {};

-  /** @type {Array.<ol.VectorTile>} */
-  var replayables = this.renderedTiles;
+  /** @type {Array.<ol.VectorImageTile>} */
+  var renderedTiles = this.renderedTiles;

  var source = /** @type {ol.source.VectorTile} */ (layer.getSource());
-  var tileGrid = source.getTileGrid();
-  var found, tileSpaceCoordinate;
+  var tileGrid = source.getTileGridForProjection(frameState.viewState.projection);
+  var sourceTileGrid = source.getTileGrid();
+  var bufferedExtent, found, tileSpaceCoordinate;
  var i, ii, origin, replayGroup;
  var tile, tileCoord, tileExtent, tilePixelRatio, tileResolution;
-  for (i = 0, ii = replayables.length; i < ii; ++i) {
-    tile = replayables[i];
+  for (i = 0, ii = renderedTiles.length; i < ii; ++i) {
+    tile = renderedTiles[i];
    tileCoord = tile.tileCoord;
-    tileExtent = source.getTileGrid().getTileCoordExtent(tileCoord, this.tmpExtent);
-    if (!ol.extent.containsCoordinate(ol.extent.buffer(tileExtent, hitTolerance * resolution), coordinate)) {
+    tileExtent = tileGrid.getTileCoordExtent(tileCoord, this.tmpExtent);
+    bufferedExtent = ol.extent.buffer(tileExtent, hitTolerance * resolution, bufferedExtent);
+    if (!ol.extent.containsCoordinate(bufferedExtent, coordinate)) {
      continue;
    }
-    if (tile.getProjection().getUnits() === ol.proj.Units.TILE_PIXELS) {
-      origin = ol.extent.getTopLeft(tileExtent);
-      tilePixelRatio = source.getTilePixelRatio();
-      tileResolution = tileGrid.getResolution(tileCoord[0]) / tilePixelRatio;
-      tileSpaceCoordinate = [
-        (coordinate[0] - origin[0]) / tileResolution,
-        (origin[1] - coordinate[1]) / tileResolution
-      ];
-      resolution = tilePixelRatio;
-    } else {
-      tileSpaceCoordinate = coordinate;
+    var sourceTiles = tile.getSourceTiles();
+    for (var t = 0, tt = sourceTiles.length; t < tt; ++t) {
+      var sourceTile = sourceTiles[t];
+      if (sourceTile.getProjection().getUnits() === ol.proj.Units.TILE_PIXELS) {
+        var sourceTileCoord = sourceTile.tileCoord;
+        var sourceTileExtent = sourceTileGrid.getTileCoordExtent(sourceTileCoord, this.tmpExtent);
+        origin = ol.extent.getTopLeft(sourceTileExtent);
+        tilePixelRatio = source.getTilePixelRatio();
+        tileResolution = sourceTileGrid.getResolution(sourceTileCoord[0]) / tilePixelRatio;
+        tileSpaceCoordinate = [
+          (coordinate[0] - origin[0]) / tileResolution,
+          (origin[1] - coordinate[1]) / tileResolution
+        ];
+        resolution = tilePixelRatio;
+      } else {
+        tileSpaceCoordinate = coordinate;
+      }
+      replayGroup = sourceTile.getReplayGroup(tile.tileCoord);
+      found = found || replayGroup.forEachFeatureAtCoordinate(
+          tileSpaceCoordinate, resolution, rotation, hitTolerance, {},
+          /**
+           * @param {ol.Feature|ol.render.Feature} feature Feature.
+           * @return {?} Callback result.
+           */
+          function(feature) {
+            var key = ol.getUid(feature).toString();
+            if (!(key in features)) {
+              features[key] = true;
+              return callback.call(thisArg, feature, layer);
+            }
+          });
    }
-    replayGroup = tile.getReplayState().replayGroup;
-    found = found || replayGroup.forEachFeatureAtCoordinate(
-        tileSpaceCoordinate, resolution, rotation, hitTolerance, {},
-        /**
-         * @param {ol.Feature|ol.render.Feature} feature Feature.
-         * @return {?} Callback result.
-         */
-        function(feature) {
-          var key = ol.getUid(feature).toString();
-          if (!(key in features)) {
-            features[key] = true;
-            return callback.call(thisArg, feature, layer);
-          }
-        });
  }
  return found;
 };


 /**
- * @param {ol.Tile} tile Tile.
+ * @param {ol.VectorTile} tile Tile.
 * @param {olx.FrameState} frameState Frame state.
 * @return {ol.Transform} transform Transform.
 * @private
@@ -308,7 +330,9 @@ ol.renderer.canvas.VectorTileLayer.prototype.handleStyleImageChange_ = function(
 * @inheritDoc
 */
 ol.renderer.canvas.VectorTileLayer.prototype.postCompose = function(context, frameState, layerState) {
-  var renderMode = this.getLayer().getRenderMode();
+  var layer = this.getLayer();
+  var source = layer.getSource();
+  var renderMode = layer.getRenderMode();
  var replays = ol.renderer.canvas.VectorTileLayer.VECTOR_REPLAYS[renderMode];
  if (replays) {
    var pixelRatio = frameState.pixelRatio;
@@ -317,40 +341,55 @@ ol.renderer.canvas.VectorTileLayer.prototype.postCompose = function(context, fra
    var offsetX = Math.round(pixelRatio * size[0] / 2);
    var offsetY = Math.round(pixelRatio * size[1] / 2);
    var tiles = this.renderedTiles;
+    var tilePixelRatio = layer.getSource().getTilePixelRatio();
+    var sourceTileGrid = source.getTileGrid();
+    var tileGrid = source.getTileGridForProjection(frameState.viewState.projection);
    var clips = [];
    var zs = [];
    for (var i = tiles.length - 1; i >= 0; --i) {
-      var tile = /** @type {ol.VectorTile} */ (tiles[i]);
-      // Create a clip mask for regions in this low resolution tile that are
-      // already filled by a higher resolution tile
-      var transform = this.getReplayTransform_(tile, frameState);
-      var currentClip = tile.getReplayState().replayGroup.getClipCoords(transform);
-      var currentZ = tile.tileCoord[0];
-      context.save();
-      context.globalAlpha = layerState.opacity;
-      ol.render.canvas.rotateAtOffset(context, -rotation, offsetX, offsetY);
-      for (var j = 0, jj = clips.length; j < jj; ++j) {
-        var clip = clips[j];
-        if (currentZ < zs[j]) {
-          context.beginPath();
-          // counter-clockwise (outer ring) for current tile
-          context.moveTo(currentClip[0], currentClip[1]);
-          context.lineTo(currentClip[2], currentClip[3]);
-          context.lineTo(currentClip[4], currentClip[5]);
-          context.lineTo(currentClip[6], currentClip[7]);
-          // clockwise (inner ring) for higher resolution tile
-          context.moveTo(clip[6], clip[7]);
-          context.lineTo(clip[4], clip[5]);
-          context.lineTo(clip[2], clip[3]);
-          context.lineTo(clip[0], clip[1]);
-          context.clip();
-        }
+      var tile = /** @type {ol.VectorImageTile} */ (tiles[i]);
+      if (tile.getState() == ol.TileState.ABORT) {
+        continue;
+      }
+      var tileCoord = tile.tileCoord;
+      var worldOffset = tileGrid.getTileCoordExtent(tileCoord)[0] -
+          tileGrid.getTileCoordExtent(tile.wrappedTileCoord)[0];
+      var sourceTiles = tile.getSourceTiles();
+      for (var t = 0, tt = sourceTiles.length; t < tt; ++t) {
+        var sourceTile = sourceTiles[t];
+        var currentZ = sourceTile.tileCoord[0];
+        var sourceResolution = sourceTileGrid.getResolution(currentZ);
+        var transform = this.getReplayTransform_(sourceTile, frameState);
+        ol.transform.translate(transform, worldOffset * tilePixelRatio / sourceResolution, 0);
+        var replayGroup = sourceTile.getReplayGroup(tileCoord.toString());
+        var currentClip = replayGroup.getClipCoords(transform);
+        context.save();
+        context.globalAlpha = layerState.opacity;
+        ol.render.canvas.rotateAtOffset(context, -rotation, offsetX, offsetY);
+        // Create a clip mask for regions in this low resolution tile that are
+        // already filled by a higher resolution tile
+        for (var j = 0, jj = clips.length; j < jj; ++j) {
+          var clip = clips[j];
+          if (currentZ < zs[j]) {
+            context.beginPath();
+            // counter-clockwise (outer ring) for current tile
+            context.moveTo(currentClip[0], currentClip[1]);
+            context.lineTo(currentClip[2], currentClip[3]);
+            context.lineTo(currentClip[4], currentClip[5]);
+            context.lineTo(currentClip[6], currentClip[7]);
+            // clockwise (inner ring) for higher resolution tile
+            context.moveTo(clip[6], clip[7]);
+            context.lineTo(clip[4], clip[5]);
+            context.lineTo(clip[2], clip[3]);
+            context.lineTo(clip[0], clip[1]);
+            context.clip();
+          }
+        }
+        replayGroup.replay(context, pixelRatio, transform, rotation, {}, replays);
+        context.restore();
+        clips.push(currentClip);
+        zs.push(currentZ);
      }
-      var replayGroup = tile.getReplayState().replayGroup;
-      replayGroup.replay(context, pixelRatio, transform, rotation, {}, replays);
-      context.restore();
-      clips.push(currentClip);
-      zs.push(currentZ);
    }
  }
  ol.renderer.canvas.TileLayer.prototype.postCompose.apply(this, arguments);
@@ -386,7 +425,7 @@ ol.renderer.canvas.VectorTileLayer.prototype.renderFeature = function(feature, s


 /**
- * @param {ol.VectorTile} tile Tile.
+ * @param {ol.VectorImageTile} tile Tile.
 * @param {olx.FrameState} frameState Frame state.
 * @param {ol.LayerState} layerState Layer state.
 * @private
@@ -399,28 +438,39 @@ ol.renderer.canvas.VectorTileLayer.prototype.renderTileImage_ = function(
  var replays = ol.renderer.canvas.VectorTileLayer.IMAGE_REPLAYS[layer.getRenderMode()];
  if (replays && replayState.renderedTileRevision !== revision) {
    replayState.renderedTileRevision = revision;
-    var tileCoord = tile.tileCoord;
-    var z = tile.tileCoord[0];
+    var tileCoord = tile.wrappedTileCoord;
+    var z = tileCoord[0];
    var pixelRatio = frameState.pixelRatio;
    var source = layer.getSource();
-    var tileGrid = source.getTileGrid();
+    var sourceTileGrid = source.getTileGrid();
+    var tileGrid = source.getTileGridForProjection(frameState.viewState.projection);
+    var resolution = tileGrid.getResolution(z);
    var tilePixelRatio = source.getTilePixelRatio();
-    var transform = ol.transform.reset(this.tmpTransform_);
-    if (tile.getProjection().getUnits() == ol.proj.Units.TILE_PIXELS) {
-      var renderPixelRatio = pixelRatio / tilePixelRatio;
-      ol.transform.scale(transform, renderPixelRatio, renderPixelRatio);
-    } else {
-      var resolution = tileGrid.getResolution(z);
-      var pixelScale = pixelRatio / resolution;
-      var tileExtent = tileGrid.getTileCoordExtent(tileCoord, this.tmpExtent);
-      ol.transform.scale(transform, pixelScale, -pixelScale);
-      ol.transform.translate(transform, -tileExtent[0], -tileExtent[3]);
-    }
-
    var context = tile.getContext();
    var size = source.getTilePixelSize(z, pixelRatio, frameState.viewState.projection);
    context.canvas.width = size[0];
    context.canvas.height = size[1];
-    replayState.replayGroup.replay(context, pixelRatio, transform, 0, {}, replays);
+    var tileExtent = tileGrid.getTileCoordExtent(tileCoord);
+    var sourceTiles = tile.getSourceTiles();
+    for (var i = 0, ii = sourceTiles.length; i < ii; ++i) {
+      var sourceTile = sourceTiles[i];
+      var sourceTileCoord = sourceTile.tileCoord;
+      var pixelScale = pixelRatio / resolution;
+      var transform = ol.transform.reset(this.tmpTransform_);
+      if (sourceTile.getProjection().getUnits() == ol.proj.Units.TILE_PIXELS) {
+        var sourceTileExtent = sourceTileGrid.getTileCoordExtent(sourceTileCoord, this.tmpExtent);
+        var sourceResolution = sourceTileGrid.getResolution(sourceTileCoord[0]);
+        var renderPixelRatio = pixelRatio / tilePixelRatio * sourceResolution / resolution;
+        ol.transform.scale(transform, renderPixelRatio, renderPixelRatio);
+        var offsetX = (sourceTileExtent[0] - tileExtent[0]) / sourceResolution * tilePixelRatio;
+        var offsetY = (tileExtent[3] - sourceTileExtent[3]) / sourceResolution * tilePixelRatio;
+        ol.transform.translate(transform, Math.round(offsetX), Math.round(offsetY));
+      } else {
+        ol.transform.scale(transform, pixelScale, -pixelScale);
+        ol.transform.translate(transform, -tileExtent[0], -tileExtent[3]);
+      }
+      var replayGroup = sourceTile.getReplayGroup(tile.tileCoord.toString());
+      replayGroup.replay(context, pixelRatio, transform, 0, {}, replays);
+    }
  }
 };
--- a/src/ol/reproj/tile.js
+++ b/src/ol/reproj/tile.js
@@ -202,7 +202,8 @@ ol.reproj.Tile.prototype.disposeInternal = function() {


 /**
- * @inheritDoc
+ * Get the HTML Canvas element for this tile.
+ * @return {HTMLCanvasElement} Canvas.
 */
 ol.reproj.Tile.prototype.getImage = function() {
  return this.canvas_;
--- a/src/ol/source/tiledebug.js
+++ b/src/ol/source/tiledebug.js
@@ -91,7 +91,6 @@ ol.inherits(ol.source.TileDebug.Tile_, ol.Tile);
 /**
 * Get the image element for this tile.
 * @return {HTMLCanvasElement} Image.
- * @override
 */
 ol.source.TileDebug.Tile_.prototype.getImage = function() {
  if (this.canvas_) {
--- a/src/ol/source/tileutfgrid.js
+++ b/src/ol/source/tileutfgrid.js
@@ -320,7 +320,6 @@ ol.inherits(ol.source.TileUTFGrid.Tile_, ol.Tile);
 /**
 * Get the image element for this tile.
 * @return {Image} Image.
- * @override
 */
 ol.source.TileUTFGrid.Tile_.prototype.getImage = function() {
  return null;
--- a/src/ol/source/vectortile.js
+++ b/src/ol/source/vectortile.js
@@ -2,9 +2,11 @@ goog.provide('ol.source.VectorTile');

 goog.require('ol');
 goog.require('ol.TileState');
+goog.require('ol.VectorImageTile');
 goog.require('ol.VectorTile');
 goog.require('ol.events');
 goog.require('ol.events.EventType');
+goog.require('ol.proj');
 goog.require('ol.size');
 goog.require('ol.source.UrlTile');

@@ -35,9 +37,8 @@ ol.source.VectorTile = function(options) {
    opaque: false,
    projection: options.projection,
    state: options.state,
-    tileGrid: options.tileGrid,
    tileLoadFunction: options.tileLoadFunction ?
-        options.tileLoadFunction : ol.VectorTile.defaultLoadFunction,
+        options.tileLoadFunction : ol.VectorImageTile.defaultLoadFunction,
    tileUrlFunction: options.tileUrlFunction,
    tilePixelRatio: options.tilePixelRatio,
    url: options.url,
@@ -51,6 +52,18 @@ ol.source.VectorTile = function(options) {
   */
  this.format_ = options.format ? options.format : null;

+  /**
+   * @private
+   * @type {Object.<string,ol.VectorTile>}
+   */
+  this.sourceTiles_ = {};
+
+  /**
+   * @type {ol.tilegrid.TileGrid}
+   */
+  this.sourceTileGrid_ = options.tileGrid ||
+      this.getTileGridForProjection(ol.proj.get(options.projection || 'EPSG:3857'));
+
  /**
   * @private
   * @type {boolean}
@@ -89,11 +102,13 @@ ol.source.VectorTile.prototype.getTile = function(z, x, y, pixelRatio, projectio
        tileCoord, projection);
    var tileUrl = urlTileCoord ?
        this.tileUrlFunction(urlTileCoord, pixelRatio, projection) : undefined;
-    var tile = new this.tileClass(
+    var tile = new ol.VectorImageTile(
        tileCoord,
        tileUrl !== undefined ? ol.TileState.IDLE : ol.TileState.EMPTY,
        tileUrl !== undefined ? tileUrl : '',
-        this.format_, this.tileLoadFunction);
+        this.format_, this.tileLoadFunction, urlTileCoord, this.tileUrlFunction,
+        this.sourceTileGrid_, this.getTileGridForProjection(projection),
+        this.sourceTiles_, pixelRatio, projection, this.tileClass);
    ol.events.listen(tile, ol.events.EventType.CHANGE,
        this.handleTileChange, this);

@@ -103,6 +118,14 @@ ol.source.VectorTile.prototype.getTile = function(z, x, y, pixelRatio, projectio
 };


+/**
+ * @inheritDoc
+ */
+ol.source.VectorTile.prototype.getTileGrid = function() {
+  return this.sourceTileGrid_;
+};
+
+
 /**
 * @inheritDoc
 */
@@ -117,6 +140,6 @@ ol.source.VectorTile.prototype.getTilePixelRatio = function(opt_pixelRatio) {
 * @inheritDoc
 */
 ol.source.VectorTile.prototype.getTilePixelSize = function(z, pixelRatio, projection) {
-  var tileSize = ol.size.toSize(this.tileGrid.getTileSize(z));
+  var tileSize = ol.size.toSize(this.getTileGridForProjection(projection).getTileSize(z));
  return [Math.round(tileSize[0] * pixelRatio), Math.round(tileSize[1] * pixelRatio)];
 };
--- a/src/ol/tile.js
+++ b/src/ol/tile.js
@@ -59,14 +59,6 @@ ol.Tile.prototype.changed = function() {
 };


-/**
- * Get the HTML image element for this tile (may be a Canvas, Image, or Video).
- * @abstract
- * @return {HTMLCanvasElement|HTMLImageElement|HTMLVideoElement} Image.
- */
-ol.Tile.prototype.getImage = function() {};
-
-
 /**
 * @return {string} Key.
 */
--- a/src/ol/tilegrid.js
+++ b/src/ol/tilegrid.js
@@ -74,7 +74,7 @@ ol.tilegrid.createForExtent = function(extent, opt_maxZoom, opt_tileSize, opt_co
 /**
 * Creates a tile grid with a standard XYZ tiling scheme.
 * @param {olx.tilegrid.XYZOptions=} opt_options Tile grid options.
- * @return {ol.tilegrid.TileGrid} Tile grid instance.
+ * @return {!ol.tilegrid.TileGrid} Tile grid instance.
 * @api
 */
 ol.tilegrid.createXYZ = function(opt_options) {
--- a/src/ol/typedefs.js
+++ b/src/ol/typedefs.js
@@ -652,8 +652,7 @@ ol.TilePriorityFunction;
 *     dirty: boolean,
 *     renderedRenderOrder: (null|ol.RenderOrderFunction),
 *     renderedTileRevision: number,
- *     renderedRevision: number,
- *     replayGroup: ol.render.ReplayGroup}}
+ *     renderedRevision: number}}
 */
 ol.TileReplayState;

--- a/src/ol/vectorimagetile.js
+++ b/src/ol/vectorimagetile.js
@@ -0,0 +1,288 @@
+goog.provide('ol.VectorImageTile');
+
+goog.require('ol');
+goog.require('ol.Tile');
+goog.require('ol.TileState');
+goog.require('ol.array');
+goog.require('ol.dom');
+goog.require('ol.events');
+goog.require('ol.extent');
+goog.require('ol.events.EventType');
+goog.require('ol.featureloader');
+
+
+/**
+ * @constructor
+ * @extends {ol.Tile}
+ * @param {ol.TileCoord} tileCoord Tile coordinate.
+ * @param {ol.TileState} state State.
+ * @param {string} src Data source url.
+ * @param {ol.format.Feature} format Feature format.
+ * @param {ol.TileLoadFunctionType} tileLoadFunction Tile load function.
+ * @param {ol.TileCoord} urlTileCoord Wrapped tile coordinate for source urls.
+ * @param {ol.TileUrlFunctionType} tileUrlFunction Tile url function.
+ * @param {ol.tilegrid.TileGrid} sourceTileGrid Tile grid of the source.
+ * @param {ol.tilegrid.TileGrid} tileGrid Tile grid of the renderer.
+ * @param {Object.<string,ol.VectorTile>} sourceTiles Source tiles.
+ * @param {number} pixelRatio Pixel ratio.
+ * @param {ol.proj.Projection} projection Projection.
+ * @param {function(new: ol.VectorTile, ol.TileCoord, ol.TileState, string,
+ *     ol.format.Feature, ol.TileLoadFunctionType)} tileClass Class to
+ *     instantiate for source tiles.
+ */
+ol.VectorImageTile = function(tileCoord, state, src, format, tileLoadFunction,
+    urlTileCoord, tileUrlFunction, sourceTileGrid, tileGrid, sourceTiles,
+    pixelRatio, projection, tileClass) {
+
+  ol.Tile.call(this, tileCoord, state);
+
+  /**
+   * @private
+   * @type {CanvasRenderingContext2D}
+   */
+  this.context_ = null;
+
+  /**
+   * @private
+   * @type {ol.format.Feature}
+   */
+  this.format_ = format;
+
+  /**
+   * @private
+   * @type {ol.FeatureLoader}
+   */
+  this.loader_;
+
+  /**
+   * @private
+   * @type {ol.TileReplayState}
+   */
+  this.replayState_ = {
+    dirty: false,
+    renderedRenderOrder: null,
+    renderedRevision: -1,
+    renderedTileRevision: -1
+  };
+
+  /**
+   * @private
+   * @type {Object.<string,ol.VectorTile>}
+   */
+  this.sourceTiles_ = sourceTiles;
+
+  /**
+   * @private
+   * @type {Array.<string>}
+   */
+  this.usedSourceTileKeys_ = [];
+
+  /**
+   * @type {string}
+   */
+  this.src_ = src;
+
+  /**
+   * @type {ol.TileCoord}
+   */
+  this.wrappedTileCoord = urlTileCoord;
+
+  /**
+   * @type {Array.<ol.EventsKey>}
+   */
+  this.loadListenerKeys_ = [];
+
+  if (urlTileCoord) {
+    var extent = tileGrid.getTileCoordExtent(urlTileCoord);
+    var resolution = tileGrid.getResolution(tileCoord[0]);
+    var sourceZ = sourceTileGrid.getZForResolution(resolution);
+    sourceTileGrid.forEachTileCoord(extent, sourceZ, function(sourceTileCoord) {
+      var sharedExtent = ol.extent.getIntersection(extent,
+          sourceTileGrid.getTileCoordExtent(sourceTileCoord));
+      if (ol.extent.getWidth(sharedExtent) / resolution >= 0.5 &&
+          ol.extent.getHeight(sharedExtent) / resolution >= 0.5) {
+        // only include source tile if overlap is at least 1 pixel
+        var sourceTileKey = sourceTileCoord.toString();
+        var sourceTile = sourceTiles[sourceTileKey];
+        if (!sourceTile) {
+          var tileUrl = /** @type {string} */
+              (tileUrlFunction(sourceTileCoord, pixelRatio, projection));
+          sourceTile = sourceTiles[sourceTileKey] = new tileClass(
+              sourceTileCoord, ol.TileState.IDLE, tileUrl, format, tileLoadFunction);
+        }
+        sourceTile.consumers++;
+        this.usedSourceTileKeys_.push(sourceTileKey);
+      }
+    }.bind(this));
+  }
+
+};
+ol.inherits(ol.VectorImageTile, ol.Tile);
+
+
+/**
+ * @inheritDoc
+ */
+ol.VectorImageTile.prototype.disposeInternal = function() {
+  var sourceTiles = this.getSourceTiles();
+  for (var i = 0, ii = sourceTiles.length; i < ii; ++i) {
+    var sourceTile = sourceTiles[i];
+    sourceTile.consumers--;
+    if (sourceTile.consumers == 0) {
+      delete this.sourceTiles_[sourceTile.tileCoord.toString()];
+      sourceTile.dispose();
+    }
+  }
+  this.tileKeys.length = 0;
+  this.sourceTiles_ = null;
+  if (this.state == ol.TileState.LOADING) {
+    this.loadListenerKeys_.forEach(ol.events.unlistenByKey);
+    this.loadListenerKeys_.length = 0;
+  }
+  if (this.interimTile) {
+    this.interimTile.dispose();
+  }
+  this.state = ol.TileState.ABORT;
+  this.changed();
+  ol.Tile.prototype.disposeInternal.call(this);
+};
+
+
+/**
+ * @return {CanvasRenderingContext2D} The rendering context.
+ */
+ol.VectorImageTile.prototype.getContext = function() {
+  if (!this.context_) {
+    this.context_ = ol.dom.createCanvasContext2D();
+  }
+  return this.context_;
+};
+
+
+/**
+ * Get the Canvas for this tile.
+ * @return {HTMLCanvasElement} Canvas.
+ * @api
+ */
+ol.VectorImageTile.prototype.getImage = function() {
+  return this.replayState_.renderedTileRevision == -1 ?
+      null : this.context_.canvas;
+};
+
+
+/**
+ * Get the feature format assigned for reading this tile's features.
+ * @return {ol.format.Feature} Feature format.
+ * @api
+ */
+ol.VectorImageTile.prototype.getFormat = function() {
+  return this.format_;
+};
+
+
+/**
+ * @return {Array.<ol.Feature>} Features.
+ */
+ol.VectorImageTile.prototype.getFeatures = function() {
+  return this.features_;
+};
+
+
+/**
+ * @return {ol.TileReplayState} The replay state.
+ */
+ol.VectorImageTile.prototype.getReplayState = function() {
+  return this.replayState_;
+};
+
+
+/**
+ * @inheritDoc
+ */
+ol.VectorImageTile.prototype.getKey = function() {
+  return this.usedSourceTileKeys_.join('/') + '/' + this.src_;
+};
+
+
+/**
+ * @return {Array.<ol.VectorTile>} Source tiles for this tile.
+ */
+ol.VectorImageTile.prototype.getSourceTiles = function() {
+  return this.usedSourceTileKeys_.map(function(sourceTileKey) {
+    return this.sourceTiles_[sourceTileKey];
+  }.bind(this));
+};
+
+
+/**
+ * @inheritDoc
+ */
+ol.VectorImageTile.prototype.load = function() {
+  var leftToLoad = 0;
+  if (this.state == ol.TileState.IDLE) {
+    this.setState(ol.TileState.LOADING);
+  }
+  if (this.state == ol.TileState.LOADING) {
+    this.usedSourceTileKeys_.forEach(function(sourceTileKey) {
+      var sourceTile = this.sourceTiles_[sourceTileKey];
+      if (sourceTile.state == ol.TileState.IDLE) {
+        sourceTile.setLoader(this.loader_);
+        sourceTile.load();
+      }
+      if (sourceTile.state == ol.TileState.LOADING) {
+        var key = ol.events.listen(sourceTile, ol.events.EventType.CHANGE, function(e) {
+          var state = sourceTile.getState();
+          if (state == ol.TileState.LOADED ||
+              state == ol.TileState.ERROR ||
+              state == ol.TileState.EMPTY) {
+            --leftToLoad;
+            ol.events.unlistenByKey(key);
+            ol.array.remove(this.loadListenerKeys_, key);
+            if (leftToLoad == 0) {
+              this.setState(ol.TileState.LOADED);
+            }
+          }
+        }.bind(this));
+        this.loadListenerKeys_.push(key);
+        ++leftToLoad;
+      }
+    }.bind(this));
+  }
+  if (leftToLoad == 0) {
+    setTimeout(function() {
+      this.setState(ol.TileState.LOADED);
+    }.bind(this), 0);
+  }
+};
+
+
+/**
+ * @param {Array.<ol.Feature>} features Features.
+ * @api
+ */
+ol.VectorImageTile.prototype.setFeatures = function(features) {
+  this.features_ = features;
+  this.setState(ol.TileState.LOADED);
+};
+
+
+/**
+ * @param {ol.TileState} tileState Tile state.
+ */
+ol.VectorImageTile.prototype.setState = function(tileState) {
+  this.state = tileState;
+  this.changed();
+};
+
+
+/**
+ * Sets the loader for a tile.
+ * @param {ol.VectorTile} tile Vector tile.
+ * @param {string} url URL.
+ */
+ol.VectorImageTile.defaultLoadFunction = function(tile, url) {
+  var loader = ol.featureloader.loadFeaturesXhr(
+      url, tile.getFormat(), tile.onLoad_.bind(tile), tile.onError_.bind(tile));
+
+  tile.setLoader(loader);
+};
--- a/src/ol/vectortile.js
+++ b/src/ol/vectortile.js
@@ -3,8 +3,6 @@ goog.provide('ol.VectorTile');
 goog.require('ol');
 goog.require('ol.Tile');
 goog.require('ol.TileState');
-goog.require('ol.dom');
-goog.require('ol.featureloader');


 /**
@@ -21,10 +19,9 @@ ol.VectorTile = function(tileCoord, state, src, format, tileLoadFunction) {
  ol.Tile.call(this, tileCoord, state);

  /**
-   * @private
-   * @type {CanvasRenderingContext2D}
+   * @type {number}
   */
-  this.context_ = null;
+  this.consumers = 0;

  /**
   * @private
@@ -51,17 +48,7 @@ ol.VectorTile = function(tileCoord, state, src, format, tileLoadFunction) {
   */
  this.projection_;

-  /**
-   * @private
-   * @type {ol.TileReplayState}
-   */
-  this.replayState_ = {
-    dirty: false,
-    renderedRenderOrder: null,
-    renderedRevision: -1,
-    renderedTileRevision: -1,
-    replayGroup: null
-  };
+  this.replayGroups_ = {};

  /**
   * @private
@@ -79,26 +66,6 @@ ol.VectorTile = function(tileCoord, state, src, format, tileLoadFunction) {
 ol.inherits(ol.VectorTile, ol.Tile);


-/**
- * @return {CanvasRenderingContext2D} The rendering context.
- */
-ol.VectorTile.prototype.getContext = function() {
-  if (!this.context_) {
-    this.context_ = ol.dom.createCanvasContext2D();
-  }
-  return this.context_;
-};
-
-
-/**
- * @override
- */
-ol.VectorTile.prototype.getImage = function() {
-  return this.replayState_.renderedTileRevision == -1 ?
-      null : this.context_.canvas;
-};
-
-
 /**
 * Get the feature format assigned for reading this tile's features.
 * @return {ol.format.Feature} Feature format.
@@ -117,14 +84,6 @@ ol.VectorTile.prototype.getFeatures = function() {
 };


-/**
- * @return {ol.TileReplayState} The replay state.
- */
-ol.VectorTile.prototype.getReplayState = function() {
-  return this.replayState_;
-};
-
-
 /**
 * @inheritDoc
 */
@@ -141,6 +100,11 @@ ol.VectorTile.prototype.getProjection = function() {
 };


+ol.VectorTile.prototype.getReplayGroup = function(key) {
+  return this.replayGroups_[key];
+};
+
+
 /**
 * @inheritDoc
 */
@@ -192,6 +156,11 @@ ol.VectorTile.prototype.setProjection = function(projection) {
 };


+ol.VectorTile.prototype.setReplayGroup = function(key, replayGroup) {
+  this.replayGroups_[key] = replayGroup;
+};
+
+
 /**
 * @param {ol.TileState} tileState Tile state.
 */
@@ -209,16 +178,3 @@ ol.VectorTile.prototype.setState = function(tileState) {
 ol.VectorTile.prototype.setLoader = function(loader) {
  this.loader_ = loader;
 };
-
-
-/**
- * Sets the loader for a tile.
- * @param {ol.VectorTile} tile Vector tile.
- * @param {string} url URL.
- */
-ol.VectorTile.defaultLoadFunction = function(tile, url) {
-  var loader = ol.featureloader.loadFeaturesXhr(
-      url, tile.getFormat(), tile.onLoad_.bind(tile), tile.onError_.bind(tile));
-
-  tile.setLoader(loader);
-};
--- a/test/spec/ol/renderer/canvas/vectortilelayer.test.js
+++ b/test/spec/ol/renderer/canvas/vectortilelayer.test.js
@@ -62,6 +62,11 @@ describe('ol.renderer.canvas.VectorTileLayer', function() {
        tileClass: TileClass,
        tileGrid: ol.tilegrid.createXYZ()
      });
+      source.getTile = function() {
+        var tile = ol.source.VectorTile.prototype.getTile.apply(source, arguments);
+        tile.setState(ol.TileState.LOADED);
+        return tile;
+      };
      layer = new ol.layer.VectorTile({
        source: source,
        style: layerStyle
@@ -156,12 +161,18 @@ describe('ol.renderer.canvas.VectorTileLayer', function() {
          tileGrid: ol.tilegrid.createXYZ()
        })
      });
-      var tile = new ol.VectorTile([0, 0, 0], 2);
-      tile.projection_ = ol.proj.get('EPSG:3857');
-      tile.features_ = [];
-      tile.getImage = function() {
+      var sourceTile = new ol.VectorTile([0, 0, 0], 2);
+      sourceTile.setProjection(ol.proj.get('EPSG:3857'));
+      sourceTile.features_ = [];
+      sourceTile.getImage = function() {
        return document.createElement('canvas');
      };
+      var tile = new ol.VectorImageTile([0, 0, 0]);
+      tile.wrappedTileCoord = [0, 0, 0];
+      tile.setState(ol.TileState.LOADED);
+      tile.getSourceTiles = function() {
+        return [sourceTile];
+      };
      layer.getSource().getTile = function() {
        return tile;
      };
@@ -192,12 +203,18 @@ describe('ol.renderer.canvas.VectorTileLayer', function() {
  describe('#forEachFeatureAtCoordinate', function() {
    var layer, renderer, replayGroup;
    var TileClass = function() {
-      ol.VectorTile.apply(this, arguments);
+      ol.VectorImageTile.apply(this, arguments);
      this.setState('loaded');
-      this.setProjection(ol.proj.get('EPSG:3857'));
-      this.replayState_.replayGroup = replayGroup;
+      var sourceTile = new ol.VectorTile();
+      sourceTile.setProjection(ol.proj.get('EPSG:3857'));
+      sourceTile.getReplayGroup = function() {
+        return replayGroup;
+      };
+      this.getSourceTiles = function() {
+        return [sourceTile];
+      };
    };
-    ol.inherits(TileClass, ol.VectorTile);
+    ol.inherits(TileClass, ol.VectorImageTile);

    beforeEach(function() {
      replayGroup = {};
@@ -223,6 +240,7 @@ describe('ol.renderer.canvas.VectorTileLayer', function() {
        layerStates: {},
        skippedFeatureUids: {},
        viewState: {
+          projection: ol.proj.get('EPSG:3857'),
          resolution: 1,
          rotation: 0
        }
--- a/test/spec/ol/source/vectortile.test.js
+++ b/test/spec/ol/source/vectortile.test.js
@@ -1,6 +1,6 @@
 goog.provide('ol.test.source.VectorTile');

-goog.require('ol.VectorTile');
+goog.require('ol.VectorImageTile');
 goog.require('ol.format.MVT');
 goog.require('ol.proj');
 goog.require('ol.source.VectorTile');
@@ -29,7 +29,7 @@ describe('ol.source.VectorTile', function() {
  describe('#getTile()', function() {
    it('creates a tile with the correct tile class', function() {
      tile = source.getTile(0, 0, 0, 1, ol.proj.get('EPSG:3857'));
-      expect(tile).to.be.a(ol.VectorTile);
+      expect(tile).to.be.a(ol.VectorImageTile);
    });
    it('sets the correct tileCoord on the created tile', function() {
      expect(tile.getTileCoord()).to.eql([0, 0, 0]);
--- a/test/spec/ol/vectorimagetile.test.js
+++ b/test/spec/ol/vectorimagetile.test.js
@@ -0,0 +1,43 @@
+goog.provide('ol.test.VectorImageTile');
+
+goog.require('ol.events');
+goog.require('ol.VectorImageTile');
+goog.require('ol.VectorTile');
+goog.require('ol.format.GeoJSON');
+goog.require('ol.proj');
+
+
+describe('ol.VectorImageTile', function() {
+
+  it('sets the loader function on source tiles', function() {
+    var format = new ol.format.GeoJSON();
+    var url = 'spec/ol/data/point.json';
+    var tile = new ol.VectorImageTile([0, 0, 0], 0, url, format,
+        ol.VectorImageTile.defaultLoadFunction,
+        [0, 0, 0], function() {}, ol.tilegrid.createXYZ(), ol.tilegrid.createXYZ(), {},
+        1, ol.proj.get('EPSG:3857'), ol.VectorTile);
+
+    tile.load();
+    var loader = tile.getSourceTiles()[0].loader_;
+    expect(typeof loader).to.be('function');
+  });
+
+  it('loader sets features on the source tile', function(done) {
+    var format = new ol.format.GeoJSON();
+    var url = 'spec/ol/data/point.json';
+    var tile = new ol.VectorImageTile([0, 0, 0], 0, url, format,
+        ol.VectorImageTile.defaultLoadFunction, [0, 0, 0], function() {
+          return url;
+        }, ol.tilegrid.createXYZ(), ol.tilegrid.createXYZ(), {},
+        1, ol.proj.get('EPSG:3857'), ol.VectorTile);
+
+    tile.load();
+    var sourceTile = tile.getSourceTiles()[0];
+
+    ol.events.listen(sourceTile, 'change', function(e) {
+      expect(sourceTile.getFeatures().length).to.be.greaterThan(0);
+      done();
+    });
+  });
+
+});
--- a/test/spec/ol/vectortile.test.js
+++ b/test/spec/ol/vectortile.test.js
@@ -1,39 +1,14 @@
 goog.provide('ol.test.VectorTile');

 goog.require('ol.events');
+goog.require('ol.VectorImageTile');
 goog.require('ol.VectorTile');
 goog.require('ol.Feature');
-goog.require('ol.format.GeoJSON');
 goog.require('ol.format.TextFeature');
 goog.require('ol.proj');


-describe('ol.VectorTile.defaultLoadFunction()', function() {
-
-  it('sets the loader function on the tile', function() {
-    var format = new ol.format.GeoJSON();
-    var tile = new ol.VectorTile([0, 0, 0], null, null, format);
-    var url = 'https://example.com/';
-
-    ol.VectorTile.defaultLoadFunction(tile, url);
-    var loader = tile.loader_;
-    expect(typeof loader).to.be('function');
-  });
-
-  it('loader sets features on the tile', function(done) {
-    var format = new ol.format.GeoJSON();
-    var tile = new ol.VectorTile([0, 0, 0], null, null, format);
-    var url = 'spec/ol/data/point.json';
-
-    ol.VectorTile.defaultLoadFunction(tile, url);
-    var loader = tile.loader_;
-
-    ol.events.listen(tile, 'change', function(e) {
-      expect(tile.getFeatures().length).to.be.greaterThan(0);
-      done();
-    });
-    loader.call(tile, [], 1, ol.proj.get('EPSG:3857'));
-  });
+describe('ol.VectorTile', function() {

  it('loader sets features on the tile and updates proj units', function(done) {
    // mock format that return a tile-pixels feature
@@ -51,7 +26,7 @@ describe('ol.VectorTile.defaultLoadFunction()', function() {
    var tile = new ol.VectorTile([0, 0, 0], null, null, format);
    var url = 'spec/ol/data/point.json';

-    ol.VectorTile.defaultLoadFunction(tile, url);
+    ol.VectorImageTile.defaultLoadFunction(tile, url);
    var loader = tile.loader_;
    ol.events.listen(tile, 'change', function(e) {
      expect(tile.getFeatures().length).to.be.greaterThan(0);