Reading a EPSG:4326 WMS layer into a Web-Mercator OpenLayers 3 map

Question

I'm a bit stumped trying to read a EPSG:4326 WMS into a OpenLayers 3 project that's using the default 3857 (Web Mercator) projection.

I'm trying to pull a WMS layer that only supports EPSG:4326, but the projection option for ImageWMS appears to be "experimental" (http://openlayers.org/en/master/apidoc/ol.source.ImageWMS.html).

Lets say I have the below. The second layer is WGS84, but the first is 3857. How do I get it to work? Is this possible with OL3? I've not found any examples with it yet.

var layers = [
  //Default 3857 layer
  new ol.layer.Tile({
    source: new ol.source.MapQuest({layer: 'sat'})
  }),

  //This layer is in WGS84 (EPSG:4326)
  new ol.layer.Image({
    extent: [0, 40, 10, 50],
    source: new ol.source.ImageWMS({
      url: 'http://demo.boundlessgeo.com/geoserver/wms',
      params: {'LAYERS': 'topp:states'},
      serverType: 'geoserver'
    })
  })
];

var map = new ol.Map({
  layers: layers,
  target: 'map',
  view: new ol.View({
    center: [-10997148, 4569099],
    zoom: 4
  })
});

Answer 1

OpenLayers 3 cannot currently reproject images for you. We are planning to work on it in the future though. But currently you can only combine image / tile layers that are in the same projection. For vector layers reprojection is possible.