Announcing: mapguide-rest 0.10

Nope, this isn't a 1.0 release. Not only are we not using decimal release numbers, but there's still plenty of things to explore and refine before we can put the 1.0 stamp on this thing. Here's what's new and changed in this release.

(Experimental) Cesium CZML support

We now have support for outputting feature data as CZML for consumption inside the Cesium 3D web viewer. Support for CZML is made available as a representation of a given Layer Definition.

For example, the following route will return data from the trees layer as CZML:

http://localhost/mapguide/rest/library/Samples/Sheboygan/Layers/Trees.LayerDefinition/features.czml

We've included a CZML example in this release that demonstrates the level of support that has been implemented for this release.

When selecting an object, its tooltip data will be shown in Cesium's information window if available.

Note the object itself has no selection indicator unless the object is a point. Still trying to figure out if we can apply a different style for selected lines and polygons.

If your Layer Definition has elevation settings applied, they be extruded if they're polygons

Now if the (experimental) tag didn't stand out, here's the current limitations with this implementation:

• The following properties are preserved when converted to CZML, anything not listed can be assumed lost in translation:
  • Point styles: Point color is preserved. The point size in CZML is the average of the height/width of the point as defined in the Layer Definition.
  • Line styles: Line color
  • Area/Polygon styles: Fill color. Outline color
• If a Layer Definition has multiple scale ranges defined, mapguide-rest will only consider the first scale range when outputting CZML
• If a given point/area/line style is themed, the default rule (the one without a filter) is ignored

Data publishing improvements

The restcfg.json now lets you specify a Layer Definition as the data source instead of a Feature Source and Feature Class name.

Also, when using a Layer Definition as a data source, you'll get tooltip, hyperlink and elevation FDO expression pre-evaluated, allowing you to use such computed properties within your templates.

You can find a new example that uses the building footprints from the Melbourne dataset.

File download support

Most GET routes can now prompt for downloads by appending download=1 to the query string of the URL.

XYZ tile improvements

Vector tiles can now be for a base layer group or for a layer within the base layer group.

Just to recap, this URL route fetches a vector tile for a given base layer group in a Map Definition

http://servername/mapguide/rest/library/{resourcePath}.MapDefinition/xyz/{groupName}/{z}/{x}/{y}/tile.{format}

If you want vector tiles for a specific layer within that group, you can use this new URL route

http://servername/mapguide/rest/library/{resourcePath}.MapDefinition/xyz/{groupName}/{layerName}/{z}/{x}/{y}/tile.{format}

You can find a new Leaflet example that uses the single-layer vector tiles.

Other changes

• Fixed bad download links in the resource data list HTML representation
• Fixed invalid chunked file transfer behavior under certain conditions
• Samples updated to use OpenLayers 3 final and Cesium 1.1

Download

Make that 3/3

Thanks to this thread, I was finally able to crack the missing piece of the CZML output puzzle for mapguide-rest, and we can now output point, line and polygon features as CZML to Cesium.

CZML is a representation of a Layer Definition in mapguide-rest, this means we will get pre-evaluated properties to play with such as:

• Tooltips
• Hyperlinks
• Elevation/Extrusion settings

We currently use this information as follows

Tooltips get written as the description property of each CZML packet, allowing such information to be displayed in the Cesium information window when the object is selected.

Now as the above screenshot shows, there's no real visual way to know what object you selected. I'm still figuring out if there's a way in CZML or the Cesium APIs to specify how a selected object looks so it can stand out.

If the Layer Definition has elevation/extrusion settings applied, that's when the fun stuff happens. We apply the extruded value in the CZML packet for each feature, giving us 2.5D features. This extrusion only applies for polygon features at the moment.

Oh, and did you know Cesium works pretty well on any WebGL capable mobile browser?

Pretty cool stuff. Now that we've nailed down the fundamentals, it's time to figure out how much visual fidelity we can preserve from MapGuide to CZML:

• Can we transfer thematics?
• Can we transfer labels?
• Can we transfer patterns?
• Others?

Fun times ahead!

2/3

After lots of trial and error, I am finally able to output features from MapGuide as CZML to Cesium via mapguide-rest

However, only 2 out of the 3 geometry types are working (points and polygons). I'm still trying to figure out:

• How to properly output CZML for line features
• How best to apply Z extrusion where it is defined in the Layer Definition
• What parts of a Layer Definition are transferable/translatable to CZML? Doesn't have to be 1:1. KML-level visual/information fidelity would suffice here.

If only there were more comprehensive CZML examples I could refer to that would make implementing this stuff much easier! All the examples I could find try to demonstrate every bell and whistle when all I want to know is where do I stick the lat/lon/elevation coordinates from my source geometries? Their CZML documentation could do with some improvement, a single-page document is terribly hard to navigate and without reference examples it's amazing I was even able to get this far!

But in the end, all this pain and struggle will be worth it because Cesium is just plain awesome! I truly believe that Cesium will be to 3D maps what OpenLayers is to 2D maps: A powerful web-based map viewing platform that is rich in features and support for many different vector and raster data sources.