Contributor's Guide

We are a community that encourages contributions. Join us. Here's how to get started.

Getting the Code

Short version:

• No commit access? Fork and clone cesium.
• Commit access? Clone cesium and make all changes in a branch.

Details

• Setup git if it isn't already (linux | mac | windows).
  • Check your settings for name and email: git config --get-regexp user.*.
  • On Windows, set git config --global core.autocrlf true (following the instructions above does this for you).
  • On Linux/Mac, set git config --global core.autocrlf input - see the GitHub help on this topic.
  • Other recommended Git settings:
    • git config --global push.default upstream - when running git push, only push the current branch.
    • git config --global branch.autosetuprebase always - when pulling remote changes, rebase your local changes on top of the remote changes, to avoid unnecessary merge commits.
• Have commit access to cesium?
  • No
    • Fork cesium.
    • Create a local repo of your fork, e.g., git clone [email protected]:yourusername/cesium.git.
  • Yes
    • Create a local cesium repo, e.g., git clone [email protected]:AnalyticalGraphicsInc/cesium.git.
    • Make non-trivial changes in a branch, e.g., git checkout -b myfeature.

Building the Code

Short version: from the root Cesium directory, run:

./Tools/apache-ant-1.8.2/bin/ant combine runServer

Then browse to http://localhost:8080/.

Details

• Cesium uses Ant for builds. Ant is included in the Cesium repo, but it requires that the Java JDK be installed.
• NodeJS is also used by some targets. The repository includes binaries, but on 64-bit Linux, you'll either need to have 32-bit libraries installed (in Ubuntu, run sudo apt-get install ia32-libs), or you can install NodeJS yourself and use a binary from your PATH by specifying -DnodePath=node when running Ant.

For a default developer build, run Ant from the root Cesium directory:

./Tools/apache-ant-1.8.2/bin/ant

The following targets can be built:

• build - A fast, developer-oriented build that prepares the source tree for use as standard Asynchronous Module Definition (AMD) modules, suitable for running tests and most examples (some Sandcastle examples require running combine). This runs automatically when saving files in Eclipse.
• combine - Runs build, plus uses NodeJS to run the RequireJS optimizer to combine Cesium and the Almond AMD loader to produce all-in-one files in the Build/Cesium directory that expose the entire Cesium API attached to a single global Cesium object. This version is useful if you don't want to use the modules directly with a standard AMD loader.
• minify - Runs combine, plus [minifies](http://en.wikipedia.org/wiki/Minification_(programming\)) Cesium.js using UglifyJS2 for a smaller deployable file.
• buildApps - Cesium doesn't require any framework, but some example applications, such as Cesium Viewer, are Dojo applications. This build target runs the Dojo build process to produce self-contained, minified, deployable versions of these applications in the Build directory.
• generateDocumentation - Generates HTML documentation in Build/Documentation using JSDoc 3.
• release - A full release build that creates a shippable product, including building apps and generating documentation.
• instrumentForCoverage - Runs JSCoverage on the source tree to allow running tests with coverage information. Use the link in index.html. Currently Windows only.
• jsHint - Runs JSHint on the entire source tree. If you use Eclipse, see below for how to run JSHint automatically as you develop.
• runServer - Launches a Jetty-based HTTP server on http://localhost:8080 for easy access to the tests, examples, and documentation. This also provides proxying for tile server providers that don't yet support CORS for retrieving tiles, which is required for use as textures.
• makeZipFile - Builds a zip file containing all release files. This includes the source tree (suitable for use from an AMD-aware application), plus the combined Cesium.js files, the generated documentation, the test suite, and the example applications (in both built and source form).
• clean - Removes all generated build artifacts.

For example, to build the release target and then start an HTTP server for testing, run:

./Tools/apache-ant-1.8.2/bin/ant release runServer

Want something fun to code? See the roadmap and start a discussion on the forum.

Setting up Eclipse

Although we encourage contributors to use their IDE of choice, many of us use Eclipse. Here is how we set it up:

• Install the Java JDK if it isn't already.

• Download the Eclipse IDE for Java Developers. Extract to a directory of your choice. Run it.

• Install additional Eclipse components: JavaScript Development Tools, Eclipse Web Developer Tools, and EGit.

  • Help - Install New Software. Work with: select Juno from the list.
  • Expand Collaboration, check Eclipse EGit.
  • Expand Programming Languages, check Eclipse JavaScript Development Tools.
  • Expand Web, XML, Java EE and OSGi Enterprise Development, check Eclipse Web Developer Tools.
  • Next, Next, Accept, Finish, wait, Not Now (we have more to install).

• Install the JSHint plugin:
  • Help - Install New Software. Work with: http://github.eclipsesource.com/jshint-eclipse/updates/.
  • Check JSHint. Next, Next, Accept, Finish, wait, Restart.

• Optional: Install the plugin for editing markdown.
• Optional: Install GLShaders for GLSL syntax highlighting: Exit Eclipse. Download GLShaders and extract into Eclipse's dropins directory.

• Run Eclipse. Close the Welcome page.

• Window - Show View - Console.

• Window - Preferences:

  • Team - Git - Configuration
    • Verify Location in User Settings tab is set to .gitconfig in the default repository directory.
    • Verify Location in Systems Settings tab is set to {Installed/Git/Location}/etc/gitconfig.
  • General - Editors - Text Editors. Check Insert spaces for tabs. OK.
  • Web - CSS Files - Editor. Switch the radio button to "Indent using spaces". Change Indentation size to 4.
  • Web - HTML Files - Editor. Switch the radio button to "Indent using spaces". Change Indentation size to 4.

• Import Cesium into your workspace: File - Import, General - Existing Projects into Workspace, Next. Fill in the path to the root Cesium directory, Finish.

• Click the "Open Perspective" button in the upper right and select JavaScript. You can then right-click on the Java perspective and close it.

• Right click on Cesium in the Script Explorer. Team - Share project. Select Git, Next. Check Use or create repository in parent directory of project. Finish.

• Configure the problems tab. The Eclipse JavaScript validator has some bugs that report incorrect warnings. Click the down arrow on the right-hand side of the Problems tab, click Configure Contents. Uncheck Show all items, Click New, then Rename the new item to Cesium. Change the Text filter to "doesn't contain" "Type mismatch: ". OK.

Development Tips

• In Eclipse, use Ctrl-Shift-R to search and open files in the workspace.

• To debug an individual test (spec), open the browser's debugger, e.g., Ctrl-Shift-I in Chrome, and click debug to the far right of the test.

Then, to step into the test, step into stepIntoThis()

• Use www.webglreport.com to see if WebGL is supported, and if so, what is exactly supported. For more goodness, including the ANGLE revision, browse to chrome://gpu-internals/ in Chrome.

• Keep your video card drivers up to date. NVIDIA | AMD.

• For WebGL debugging such as stepping through draw calls, viewing textures and vertex buffers, etc., use the WebGL Inspector.

• To run without ANGLE (Windows-only)

  • Chrome: Run with the --use-gl=desktop argument. Make sure you close all Chrome windows before starting.
  • Firefox: Browse to about:config and set webgl.prefer-native-gl to true.

• To debug shader problems when running with ANGLE enabled, it's sometimes useful to look at the generated HLSL code. To do that, run Chrome with the --enable-privileged-webgl-extensions command-line option. Then, obtain the HLSL code by executing: var hlsl = gl.getExtension("WEBGL_debug_shaders").getTranslatedShaderSource(fragmentShader)

• For performance testing, turn off vsync

  • In the driver, e.g., the NVIDIA Control Panel or the Catalyst Control Center.
  • Also turn off VSync in Chrome: browse to chrome://flags/ and check Disable GPU VSync.

• For an FPS counter in Chrome, browse to chrome://flags/ and check FPS counter. Create a FPS counter in Cesium with PerformanceDisplay

Contributing Code

• Send us a pull request. We'll promptly review it, provide feedback, and merge it.
• Before we can merge, we require a Contributor License Agreement (CLA). This can be emailed to [email protected], and only needs to be completed once. The CLA ensures that you retain copyright to your contributions, and that we have the right to use them and incorporate them into Cesium. There is a CLA for individuals and corporations. Please email completed CLAs and related questions to [email protected].
• Please make sure:
  • Your code follows the coding conventions.
  • Your code passes JSHint. We use the JSHint Eclipse plugin so it runs automatically when we save. You can also run the jsHint Ant task from the command line.
  • To include tests with excellent code coverage for new features. We use Jasmine for writing tests. Run them by browsing to http://localhost:8080/Specs/SpecRunner.html. Verify all new and existing tests pass. For bonus points, test Chrome, Firefox, and other browsers supporting WebGL.
  • To update LICENSE.md if third-party libraries were added/updated/removed, including version bumps. Mention it in CHANGES.md.
  • Were new public classes, functions, or properties added?
    • Include reference documentation with code examples. Check out the best practices.
    • Update CHANGES.md.
    • If the change is significant, add a new Sandcastle example or extend and existing one.

What Next?

Read about the Cesium's architecture; check out the roadmap; join the forum; and start hacking.