3D Engines

Looking for a quick overview of the 3D Engines available through EarthSLOT? You're in the right place.

All of these engines share several awesome features in common, such as the ability to interactively fly around the planet and see any resolution data. The strengths and weaknesses we list below are largely those that set the engines apart.

Skyline Software / EarthSLOT
Overview	Skyline sells a product that gives users the power to create and serve their own Earth Models and Applications on disk or over the internet. EarthSLOT uses Skyline's software and presents it to the public as a service to create custom Earth Models and host earth science applications based on them (that is, EarthSLOT is a customer of Skyline).
URL	http://www.skylinesoft.com -- Skyline's web page http://www.earthslot.org -- our implemenation of Skyline's engine
Software names	TerraExplorer, TerraExplorer Pro, TerraBuilder, TerraGate, TerraPhoto3D
Strengths	- Allows for easy creation of Applications using TerraExplorer Pro - Can easily create fully automated applications that tour users around, but allow them to break off and explore on their own - A full-featured API allows for custom tool creation (like new measurement tools, custom web interfaces with increased/decreased functionality, etc). Using the API, savvy users do not need to purchase any software to make custom content, though this is recommended simply because it so good - Both global and planar Earth Models can be created, and these can saved as stand-alone applications not requiring internet access - Their Collaboration Tool allows a user to control the screens of an unlimited number of other users as they fly around -- great for distance education, scientific collaboration, disaster management, etc. - TerraPhoto3D is a pure HTML client that can be used on Macintosh or Unix machines to access the same Earth Models one frame at a time
Weaknesses	- At this time, trials and purchases of the Pro version are not automated, slowing down new users from trying it out - The free viewer cannot be used to make any modifications or customizations
Matt's Recommendations	Use these resources if you want to create educational packages with full automation, custom viewers within your own web pages, or if you have your own imagery that you would like to see in 3D (contact us to create the latter).
Peter's Recommendations	Skyline's engine is by far the most easily customizable using the provided API which can be accessed from any COM capable language (VBScript, JavaScript, C#, C++, etc.). While other engines do offer the ability to create portable content (content that doesn't require an Internet connection), Skyline's engine is the only one that can be used to create 100% portable content to be used on any removable media. The variety of tools that are implemented in this engine makes Skyline/EarthSLOT a good choice for users who want to do more than just look at the Earth.
Forum links	Skyline's forum EarthSLOT forum about Skyline

User Interface - Skyline's TerraExplorer

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Google Earth
Overview	Google Earth primarily sells a service using a 3D engine (based on Keyhole's technology). Though you can buy the engine itself, you must purchase seats for end-users, meaning that there is no free viewer open to unlimited users.
URL	http://earth.google.com
Software names	Google Earth, Google Earth Plus, Google Earth Pro
Strengths	- Backed by Google's huge server infrastructure, ensuring fast connections and 100% up time, probably for eternity. - Backed by Google's huge staff of talented techs and aggressive business-to-business marketers - Huge user-base contributing new content and tools daily - Huge sets of GIS layers come standard, such as restaurants, driving directions, and the like, great for tourism and retail - The KML language makes it easy to write your own scripts to automatically update your applications to include new data (like recent earthquakes or satellite imagery) - Has a very extensive database of high resolution imagery, particularly over cities
Weaknesses	- Being a for profit service, their functionality is going to be limited to those features they think are profitable to them, so their flexibility is not as great as other packages. - Their GIS support is marginal, with large shapefiles having difficulty displaying and some misregistration to their spherical (non-elliptical) earth model
Matt's Recommendations	It is an awesome tool, great for sharing locational information and simple educational content because it can handle unlimited user loads. I'm still not sure of its accuracy in terms of being a scientific GIS as they use a spheroid instead of an ellipsoid and some of layers didnt line up correctly; we also had trouble with large shapefiles. But they are not aiming to be a science tool, but a consumer tool, where accuracies to better than several meters are not necessary.
Peter's Recommendations	From a performance perspective Google Earth (GE) clearly leads the pack. The speed at which the data is delivered over even low-bandwidth DSL connections is impressive. Google Earth also includes the most high resolution data at this time. Unfortunately GE currently offers virtually no interface customization, terrain analysis, or other real GIS capabilities. It will be interesting to see where Google's nearly unlimited resources will take GE in the future.
Forum link	Google's forum EarthSLOT forum about Google Earth
Related links	http://www.gearthblog.com/ http://go.ogleearth.com/ http://www.googleearthhacks.com/ http://www.kmz-archive.com/

User Interface - Google Earth

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World Wind
Overview	This is the only truly open source 3D engine, where the entire code is accessible.
URL	http://worldwind.arc.nasa.gov/
Software names	World Wind 1.3
Strengths	- Totally open source, allowing unlimited customization
Weaknesses	- No slick user interfaces to put the power of the customizations into the hands of non-programmers
Matt's Recommendations	The 125 MB initial download is kind of a bear, but it does allow you work with it offline. I rarely use it simply because I get everything I need from EarthSLOT and GoogleEarth, which are much easier to customize as they have consumer-level software that makes customizations so easy.
Peter's Recommendations	The World Wind interface is minimalistic, yet well implemented. World Wind doesn't allow for much user interaction, and thus has no need for a complex user interface. Since World Wind is an open source project, interested parties are able to customize their viewer as they please if they have the skills needed to do so. Click here to learn more about accessing their source code. The one feature that makes World Wind stand out is the ability to instantly apply vertical exaggeration to the terrain.
Forum link	World Wind's forum EarthSLOT's forum about World Wind
Related links	http://www.worldwindcentral.com/hotspots/

User Interface - World Wind


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GeoFusion
Overview	GeoFusion offers both a product and service, in that you can fly around the Earth Models they have created or buy their software and create your own.
URL	http://www.geofusion.com/ http://www.geoplayer.com
Software names	GeoMatrix Toolkit, GeoPlayer
Strengths	- Ability to fade between different streamed imagery layers - Handles multiple iimagery and terrain data inserts - Highly customizable user interface - Supports access to multiple local and remote data feeds - API allows creation of wide range of applications - Free GeoPlayer activeX control can run in IE browser, Macromedia Director, or other compatable containers - GeoPlayer web interface can be tailored for the data displayed using HTML or Flash with JavaScript. - Provides more efficient and superior quality polar rendering than other systems.
Weaknesses	- Flight controls are designed around a mouse rather than keyboard - No modifications are possible with the free viewer, at this time, but an authoring tool and tile server are apparently in the works
Matt's Recommendations	It's an awesome tool, and clearly it's greatest strength is the ability to fade between different imagery layers while in 3D, which none of the other engines are currently doing. At the present time, it's utility as a customizable GIS is limited to those who have purchased the full package.
Peter's Recommendations	I can't really say much about this as I have only tried the free viewer for a short period of time. The implementation of the ability to fade between imagery layers is much better than in Google Earth. It seems that the GeoMatrix Toolkit, which would allow end-users full customization of the viewer application, is C++ based. While C++ is a great choice for those who wish to truly build their own highly customized viewers, it will likely discourage the average user from attempting to modify the user interface or functionality.
Forum link	EarthSLOT's forum about GeoFusion

 

 

Performance Considerations between engines

Each of the 3D Engine has different performance limitations. Skyline products will install on pretty much any Windows system, though it may have trouble on some Windows98. World Wind is not picky when it comes to installations either. Google Earth will not install unless your screen resolution is at least 1024x768 and your desktop color depth is 32-bit.

The Skyline 3D engine used by EarthSLOT has the advantage that it doesn't necessarily require an Internet connection. At EarthSLOT we can create highly portable content that will fit on a USB Flash Drive, CD, or DVD, so that the end user can be mobile with the 3D visuaization. This is especially useful for scientific fieldwork, or under any other circumstance in which a fast Internet connection is not guaranteed. The amount of imagery within such applications is obviously limited by the size of the disk; our main earth model is over 2 TB.

The online delivery of EarthSLOT does rely on a fast Internet connection. While I have received feedback from a European user who found the speed of his 128kb/s ISDN connection acceptable, I would personally recommend at to get as fast of a connection as you possibly can. Since EarthSLOT is co-located on an Internet2 site, other Internet2 users will be able to access this service at the highest possible connection speed.

End users of the Skyline 3D engine through EarthSLOT will have to keep in mine that this is a project that is being run with limited resources at this time. The EarthSLOT transfer speeds generated by the our single server rather than the hundreds of computers world-wide serving GoogleEarth, and thus its performance may be comparitively limited at times.

Google Earth delivers the best performance when it comes to data transfer speeds between the GE servers and the end user. NASA's World Wind is somewhat of a hybrid, where the initial data the end user sees is installed with the application, and only once the user zooms in to obtain a greater level of detail, then the NASA OnEarth server is contacted to stream additional data. The main problem is that the OnEarth server is quite often experiencing severe overload and the response times are very long to a point where data requests time out.

Google Earth is the most hardware demanding engine of the three, followed by Skyline/EarthSLOT, with NASA's World Wind having very modest hardware requirements. Generally speaking a fast Internet connection and a high end graphic card are recommended for either 3D engine.

GeoFusion's product does a great job of streaming multiple imagery layers, which clearly seems to be one of its strength in terms of performance. At the moment, there is a bit of a lag of the initial low res imagery (showing a black screen until it comes in), but the ability to blend between massive imagery layers smoothly is truly a powerful feature.

Feature Comparison

Skyline leads then way when it comes to importing vector based data and 3D object support and use as a scientific GIS. Google Earth does offer a GIS data import extension (for $200/annually), but in comparison to the Skyline's feature rich built-in capability the GE importer is clunky at best. World Wind provides extremely limited GIS data import capabilities and those who wish to add their own data need to be familiar with writing add-on features for World Wind. GeoFusion also has the ability to turn on and off GIS layers, but it seems to work along the lines of a traditional IMS where the interface used for layer control is customized for each application.

Skyline also provides a large number of tools for terrain and situational analysis (such as viewshed analysis, contour map generation on the fly, just to name a couple), clearly showing Skyline's upbringing in the defense, intelligence, and homeland security sector. Google Earth only provides rudimentary distance and area (paid version only) measurement tools, while World Wind trails the pack with very limited analysis capabilities.

GoogleEarth currently provides the easiest means to import your own imagery. However, the method they use for this is not as slick as the streamed based imagery. That is, any user-imported imagery must be downloaded completely before being displayed; tiliing speeds the downloading of larger tiles. An added complicated to this is that the user-supplied imagery comes from the user's own server, not Google's, which can substantially increase download times.

The one feature that makes World Wind stand out is the ability to instantly apply vertical exaggeration to the terrain. While Skyline supports different exaggerations as well, they need to be pre-set before the end user accesses the data. There is no elevation exaggeration support in Google Earth. We do not apply vertical exageration to most of our earth models created with Skyline, as this affects the measurement tools involving vertical distances.

Skyline also offers several features not found in the other packages. Users can embed a 3D window into their own web pages, for example, using the API to create a custom viewer. There is also a collaboration tool, whereby one user can control the screens of unlimited other users while flying around; this tool is currently only available using the Pro version of TerraExplorer, but using the API someone could code an open source version of this.

GeoFusion offers the GeoMatrix Toolkit, a C++ SDK for building earth visualization applications and a free web-based viewer called GeoPlayer. Their core GeoMatrix technology renders imagery, terrain, vector, and annotation data on the globe using a multiresolution tiling system. The GeoMatrix Toolkit can be used to program your own commercial level applciations (ESRI used it for ArcGlobe) where you can add your OpenGL graphics for drawing any content you want on the globe. GeoPlayer is their new web streaming player that can access both local and multiple remote data feeds to create a virtual planet. It is based on the same GeoMatrix technology and has an API that allows full control of the view and obejcts placed on the globe. It is designed to create custom "gateways" or digital planetary content for telling your story and is supported by fly to and full animation path functionality. GeoPlayer will soon be followed up with an authoring tool and tile server. GeoFusion also provides software integration services.

Open Source / Customization

Only World Wind is open source when it comes to the 3D engine itself. This opens to possibility to end users to highly customize or completely rewrite the client and its flight performance capabilities, if the end user has the appropriate skills to do so. It is rather difficult to add 3rd party content to the World Wind application as it requires the creation of an add-on. The World Wind source documentation is complete, but requires solid knowledge of programming techniques.

While the Skyline viewer as such is not open source code, Skyline does provide an extensive API to access the viewer applications function from within any COM-capable language (eg., VB, VB script, C++, C#). This allows end users to integrate the client in their own applications, completely rewrite the client as stand alone application, or embedd the client into a web browser. The API is well documented, including examples in different programming languages, making it easy to create custom content.

Google Earth is not open source either, and there is nothing the end-user can do to customize the user interface as previously mentioned. Google does provide access to the specifications needed to create application files. Google's KML specifications are well documented and examples are provided through the Google Earth Community BBS. Thus, highly automated routines can be created to ingest frequently-updated satellite imagery or database information like recent earthquakes, then post these on the web such that the end-user always accesses the most recent data from the same link.