ondrej_1974
With all due respect to the folks at AGI and the amazing work they put to CesiumJS, Melown is a very different product tailored at different use cases. We developed Melown bottom-up as a platform for interactive rendering True3D (photogrammetric or lidar based) data, at street-level detail and planetary scale. Cesium on the other hand, is essentially a 2.5D (DEM) rendering library with some interesting add-ons.
Melown now natively supports 2.5D data and Cesium has incorporated support for True3D data through its "3D tiles" standard. This makes the two systems look similar in appearance, though they are by no means similar by design and there differences show once you work with anything more complex than simple demos.
As one of the authors of Melown (and a person with only very limited knowledge of Cesium) I tend to see many advantages in Melown data model, such as support for multiple reference frames (see [0] and [1]), powerful data integration capabilities, state of the art geodata rendering (complete with styles similar to the ones used by Mapbox), and most importantly, performance when dealing with large scale True3D data. Cesium users would probably point out to its support for temporal datasets and wide-array of connectors for various GIS formats.
In the end the choice depends on where your priorities are. I sincerely doubt you could base a website such as the one at [2] on Cesium due to some important data integration issues. Perhaps some people more knowledgeable of Cesium might prove me wrong.
Of course, there is one more important difference between Cesium and Melown. Melown, at this time, is not yet fully open-sourced yet. But that difference is not going to be there much longer. We at Melown will be open-sourcing not only the JS library, but much of the server-side data management software, hopefully providing web and desktop/mobile software developers with whole new array of choice when dealing with the challenges of modern 3D mapping application development.
[0] https://melown.com/mercury [1] http://tinyurl.com/zk6xqnq [2] https://melown.com/intergeo2016
Actually, Melown is all about scalability. There is no limit to the size of True3D data we can integrate, appart from the disk space available.
To get an idea of what I am talking about, please check out the simple demo at https://melown.com/intergeo2016
Yes, we're talking planetary scale. If somebody had the resources to model the entire planet in 10cm True3D, Melown can carry it, with no changes to the existing architecture.
And unlike Google, Melown can do polar caps too, the same quality as any other place on Earth. And with Melown, you can do Mars, Mercury, Titan, Europa, or any other celestial object, without the limitation of Web Mercator, WGS84 or other simplistic approaches.