This project contains Java packages and asset packs, developed for sgold's jMonkeyEngine games, which might prove useful in similar projects. It includes the SkyControl library for sky simulation.

Summary of SkyControl features:

• sun, moon, stars, horizon haze, and up to six cloud layers
• compatible with static backgrounds such as cube maps
• high resolution textures are provided -- or customize with your own textures
• compatible with effects such as SimpleWater, shadows, and bloom
• continuous and reversible motion and blending of cloud layers
• option to foreshorten clouds near the horizon
• continuous and reversible motion of sun, moon, and stars based on time of day
• updater to synchronize lighting and shadows with sun, moon, and clouds
• continuous scaling of sun, moon, and clouds
• option for continuously variable phase of the moon
• demonstration apps and online tutorial provided
• complete source code provided under FreeBSD license

All package names in this project begin with "jme3utilities". The source files are in JDK 7 format with CRLF line endings.

Since September 2015, this project has been hosted at https://github.com/stephengold/jme3-utilities

From November 2013 to September 2015, it was hosted at http://code.google.com/p/jme3-utilities

This project is available in plugin (read-only) form. Somewhat confusingly, the plugin is named "SkyControl".

The SkyControl plugin is derived from this project. It is more stable, but usually less advanced. It doesn't include every package and asset in the project.

The plugin is available from the jMonkeyEngine User Contributions Update Center:

• updates from http://updates.jmonkeyengine.org/contributions/updates.xml
• repository hosted at https://github.com/jMonkeyEngine-Contributions
• archived SVN repo at https://code.google.com/p/jmonkeyplatform-contributions

The SkyControl plugin consists of five libraries:

• SkyControl: basic utility classes, math, and sky simulation (3 packages + assets)
• jme3-utilities-debug: test/debug aids (1 package)
• jme3-utilities-nifty: support for Nifty user interfaces (1 package + assets)
• jme3-utilities-ui: action-oriented user interfaces (1 package + assets)
• jme3-utilities-x: scene controls, navigation, physics, and XML (4 packages)

If you plan to modify code or assets (or if you need any package not included in the plugin), then you'll need to install the complete jme3-utilities project.

1. Download the jMonkeyEngine SDK from http://hub.jmonkeyengine.org/downloads
2. Install the SDK, which includes:

• the engine itself,
• an integrated development environment (IDE) based on NetBeans, and
• the Blender 3D application.

The hardware and software requirements of the SDK are documented at http://hub.jmonkeyengine.org/wiki/doku.php/jme3:requirements

Clone the JME3 Utilities Package source files using Git:

1. Open the Clone wizard in the IDE:

• Menu bar -> "Team" -> "Git" -> "Clone..."

2. For "Repository URL:" specify "https://github.com/stephengold/jme3-utilities.git" (without the quotes).
3. Clear the "User:" and "Password:" text boxes.
4. Click on the "Next >" button.
5. Make sure the "master" remote branch is checked.
6. Click on the "Next >" button again.
7. For "Parent Directory:" specify a writable folder on a local filesystem or a non-existent subfolder of such a folder.
8. Make sure the "Scan for NetBeans Projects after Checkout" box is checked.
9. Click on the "Finish" button.

There will be problems due to a missing JAR file. Do not attempt to resolve them yet!

1. Download the JCommander version 1.48 JAR file from "http://mvnrepository.com/artifact/com.beust/jcommander/1.48" to the "jars" folder of the new project.

2. If you plan to generate your own star maps, download the ASCII version of version 5 of the Yale Bright Star Catalog from "http://tdc-www.harvard.edu/catalogs/bsc5.html" to the "assets/Textures/skies" folder of the new project.

1. (optional) Rename the project:

• Right-click on the jme3-utilities project in the "Projects" window.
• Select "Rename...".
• Type a new name in the text box.
• Click on the "Rename" button.

2. Add the downloaded JAR to the project:

• Open the project's properties in the IDE:
• Right-click on the new project (not its assets) in the "Projects" window.
• Select "Properties".
• Under "Categories:" select "Libraries".
• Click on the "OK" button.

3. Build the project's JARs:

• Right-click on the new project in the "Projects" window.
• Select "Clean and Build".

4. (optional) Generate the project's javadoc:

• Right-click on the new project in the "Projects" window.
• Select "Generate Javadoc".

Note: The source files are in JDK 7 format, but the IDE creates new JME3 projects in JDK 5 format.

SkyControl is a reusable sky simulation for jMonkeyEngine games.

Adding it to an existing JME3 project should be a simple six-step process:

1. Add the JME3 Utilities Package JARs to the project.
2. Disable any existing sky which might interfere with SkyControl.
3. Add a SkyControl instance to some node in the scene graph.
4. Configure the SkyControl instance.
5. Enable the SkyControl instance.
6. Test and tune as necessary.

To demonstrate this process, we'll apply it to BasicGame and then to CubeMapExample, a more sophisticated application. I encourage you to follow along in your development environment.

You'll need:

• A development machine with Java and the JME3 SDK installed.
• A clean install of the JME3 Utilities Package.
• A clean instance of the BasicGame project.

To instantiate the BasicGame Project:

1. Open the "New Project" wizard in the IDE:
2. Menu bar -> "File" -> "New Project..."
3. Under "Categories:" select "JME3".
4. Under "Projects:" select "BasicGame".
5. Click on the "Next >" button.
6. For "Project Location:" specify a new folder on a local filesystem.
7. Click on the "Finish" button.

If you're unfamiliar with BasicGame, you may wish to run it (and/or examine the source code) to see how it works before modifying it.

Open the project's properties in the IDE:

1. Right-click on the BasicGame project (not its assets) in the "Projects" window.
2. Select "Properties".
3. Under "Categories:" select "Libraries".
4. Click on the "Compile" tab.
5. If the SkyControl plugin is installed, then the SkyControl library can provide the required JARs:

• Click on the "Add Library..." button.
• Select the "SkyControl" library.
• Click on the "Add Library" button.
• Click on the "OK" button.

6. If the SkyControl plugin is not installed, then two JARs are required, one for classes and one for assets:

• Click on the "Add JAR/Folder" button.
• Navigate to the folder where you installed the JME3 Utilities Package and then to the "dist" folder therein.
• Select the "jME3-utilities.jar" file.
• Click on the "Open" button.
• Click on the "Add JAR/Folder" button again.
• Navigate to the "lib" folder.
• Select the "jME3-utilities-assets.jar" file.
• Click on the "Open" button again.
• Click on the "OK" button.

Since BasicGame comes without any sky simulation -- just the default (black) viewport background -- there is nothing to remove.

The scene graph of BasicGame has only one node, the root node. The root node is typically a good place to add SkyControl.

1. Open the "Main.java" source file in the IDE:

• In the "Projects" window, expand the BasicGame project node.
• Expand the "Source Packages" node under the BasicGame project.
• Expand the "mygame" package under "Source Packages".
• Select "Main.java" file under the "mygame" package.
• Double-click to open the file.

2. In the import section of "Main.java", add the following code:

   import jme3utilities.sky.SkyControl;
   

3. Scroll down to the simpleInitApp() method and insert the following code just before the final close-brace:

   SkyControl sc = new SkyControl(assetManager, cam, 0.9f, true, true);
   rootNode.addControl(sc);
   

The parameters of the constructor are documented in the JavaDoc for the SkyControl class.

By default, SkyControl simulates midnight on March 21st in Wiltshire, England, with no clouds and a full moon. Instead, let's configure 6 a.m. on February 10th in Sunnyvale, California with dense clouds:

1. In the import section of "Main.java", add the following code:

   import com.jme3.math.FastMath;
   import java.util.Calendar;
   

2. In simpleInitApp(), insert the following code just before the final close brace:

   sc.getSunAndStars().setHour(6f);
   sc.getSunAndStars().setObserverLatitude(37.4046f * FastMath.DEG_TO_RAD);
   sc.getSunAndStars().setSolarLongitude(Calendar.FEBRUARY, 10);
   sc.setCloudiness(1f);
   

Other configuration methods are documented in the JavaDoc for the SkyControl, SunAndStars, and Updater classes.

Unlike most JME3 controls, SkyControl instantiates in a disabled state. In order to see the sky, you must enable the control:

1. In simpleInitApp(), insert the following code just before the final close-brace:

   sc.setEnabled(true);
   

To test the modified BasicGame, right-click in the "Main.java" editor window and select "Run File (Shift+F6)".

Sometimes you'll want to combine SkyControl with other sky elements. The JME3 Utilities Packages includes CubeMapExample, a slightly more sophisticated application than BasicGame. CubeMapExample includes a cube-mapped sky, lit terrain, and multiple light sources. In this section, you'll see how SkyControl can be used to add sun, moon, and clouds to CubeMapExample.

In the Projects window of the IDE, navigate to the "jme3utilities.sky.test" source package. Open the "CubeMapExample.java" file and study the code.

Since CubeMapExample is part of the JME3 Utilities Package, there are no libraries to add. And since we plan to use the existing cube map, there's nothing to remove.

Both SkyFactory and SkyControl add geometries to Bucket.Sky. In the absence of a custom GeometryComparator, geometries in this bucket are rendered in scene graph order. Since the cube map is opaque, we want to SkyControl to add its geometries after the sky cube in the scene graph.

1. In the import section of "CubeMapExample.java", add the following code:

   import jme3utilities.sky.SkyControl;
   

2. Scroll down to the initializeSky() method and insert the following code just before the final close-brace:

   SkyControl sc = new SkyControl(assetManager, cam, 0.8f, false, true);
   rootNode.addControl(sc);
   

For now, we'll turn star motion off, since that simplifies things. The lower value (0.8) for cloud flattening will make it easier to compensate for the scene's low horizon.

1. It's very important to disable the control's built-in star maps so that the cube map's stars will be visible at night:

   sc.clearStarMaps();
   

2. Adjust the cloudiness so that clouds will be visible:

   sc.setCloudiness(0.8f);
   

In initializeSky(), insert the following code just before the final close-brace:

    sc.setEnabled(true);

At this point, the application should run successfully. However, for the best possible result, it needs some tuning.

1. To lower the edge of the cloud dome so that it's hidden by the terrain, add the following code:

   sc.setCloudYOffset(0.4f);
   

2. To see the scene in daylight, add this:

   sc.getSunAndStars().setHour(12f);
   

3. To synchronize the lights with SkyControl, add this to the import section:

   import com.jme3.light.Light;
   

   and this to the end of the initializeSky() method:

   for (Light light : rootNode.getLocalLightList()) {
       if (light.getName().equals("ambient")) {
           sc.getUpdater().setAmbientLight((AmbientLight) light);
       } else if (light.getName().equals("main")) {
           sc.getUpdater().setMainLight((DirectionalLight) light);
       }
   }
   

The uneven shading of the level terrain is due to sunlight coming in at a low angle. Since it's noon, the easiest way to raise the sun's elevation is to decrease the observer's latitude. Try, for instance:

sc.getSunAndStars().setObserverLatitude(0.2f);

The sun looks like a boring white disc in the southern sky. For a more impressive sun, apply a bloom filter to it:

import com.jme3.post.filters.BloomFilter;
import jme3utilities.Misc;

...

BloomFilter bloom = new BloomFilter(BloomFilter.GlowMode.Objects);
bloom.setBlurScale(2.5f);
bloom.setExposurePower(1f);
Misc.getFpp(viewPort, assetManager).addFilter(bloom);
sc.getUpdater().addBloomFilter(bloom);

To add star motion, it's not sufficient simply to change the control's constructor from

SkyControl sc = new SkyControl(assetManager, cam, 0.8f, false, true);

to SkyControl sc = new SkyControl(assetManager, cam, 0.8f, true, true);

It's also necessary to rotate the cube map to match SkyControl's notions of time and space. To achieve this, override the application's simpleUpdate() method:

@Override
public void simpleUpdate(float unused) {
    Spatial starMap = rootNode.getChild("Sky");
    SkyControl sc = rootNode.getControl(SkyControl.class);
    sc.getSunAndStars().orientExternalSky(starMap);
}

To simulate the passage of time, we need state and a mechanism to update it. The jme3utilities.TimeOfDay class is an app state which addresses this need.

1. Import the class:

   import jme3utilities.TimeOfDay;
   

2. Declare a field in CubeMapExample:

   TimeOfDay timeOfDay;
   

3. Initialize and attach it in simpleInitApp():

   timeOfDay = new TimeOfDay(19f);
   stateManager.attach(timeOfDay);
   timeOfDay.setRate(1000f);
   

   All that remains is to update the control.

4. Add two lines to simpleUpdate(), right before the invocation of orientExternalSky():

   float hour = timeOfDay.getHour();
   sc.getSunAndStars().setHour(hour);
   

For a demonstration of the more advanced features of SkyControl, you may wish to study the TestSkyControl class in the "jme3utilities.sky.test" package.

External links:

• November 2013 SkyControl demo video: https://www.youtube.com/watch?v=FsJRM6tr3oQ
• January 2014 SkyControl update video: https://www.youtube.com/watch?v=gE4wxgBIkaw
• maze game which uses jme3-utilities: https://github.com/stephengold/jme3-maze

Like most projects, the jme3-utilities project builds upon the work of many who have gone before.

I therefore acknowledge the following software developers:

• Cris (aka "t0neg0d") for creating SkyDome (which provided both an inspiration and a starting point for SkyControl) and also for encouraging me to run with it ... thank you yet again!
• Paul Speed, for helpful insights which got me unstuck during debugging
• the brave souls who volunteered to be alpha testers for SkyControl, including:
  • Davis Rollman
  • "Lockhead"
  • Jonatan Dahl
  • Mindaugas (aka "eraslt")
  • Thomas Kluge
  • "pixelapp"
  • Roger (aka "stenb")
• the beta testers for SkyControl, including:
  • "madjack"
  • Benjamin D.
  • "Fissll"
  • Davis Rollman
• the creators of (and contributors to) the following software:
  • Adobe Photoshop Elements
  • the Blender 3D animation suite
  • the FindBugs source code analyzer
  • Gimp, the GNU Image Manipulation Program
  • the Git and Subversion revision control systems
  • the Google Chrome web browser
  • Guava core libraries for Java
  • the Java compiler, standard doclet, and runtime environment
  • the JCommander Java framework
  • jMonkeyEngine and the jME3 Software Development Kit
  • LWJGL, the Lightweight Java Game Library
  • Microsoft Windows
  • the NetBeans integrated development environment
  • the Nifty GUI
  • Open Broadcaster Software
  • the PMD source code analyzer
  • the RealWorld Cursor Editor
  • Alex Peterson's Spacescape tool
  • the WinMerge differencing and merging tool

Many of SkyControl's assets were based on the works of others who licensed their works under liberal terms or contributed them to the public domain. For this I thank:

• Cris (aka "t0neg0d")
• Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC
• Tom Ruen

I am grateful to Google Code and Github for providing free hosting for the jme3-utilities project and many other open-source projects.

I'm also grateful to Julian (for lending me one of his microphones) and finally my dear Holly, for keeping me sane.

If I've misattributed anything or left anyone out, please let me know so I can correct the situation.