The KK Physics Project is about integrating the Jolt Physics engine into the jMonkeyEngine (JME) game engine.

This project is currently under development and is not intended for production use.

It contains 2 subprojects:

1. library: the KK Physics JVM runtime library and its automated tests
2. apps: non-automated test software

Complete source code (in Java) is provided under a 3-clause BSD license.

Contents of this document

• How to add KK Physics to an existing project
• How to build KK Physics from source
• External links
• Acknowledgments

How to add KK Physics to an existing project

KK Physics comes pre-built as a single JVM library that can be downloaded from Maven Central or GitHub.

KK Physics replaces (and is thus incompatible with) the jme3-bullet, jme3-jbullet, and Minie libaries. Before adding KK Physics to a project, you should remove those libraries so they won’t interfere with KK Physics.

For projects built using Maven or Gradle, it is sufficient to add dependencies on the KK Physics library and appropriate jolt-jni native libraries. The build tool should automatically resolve the remaining dependencies.

Current jolt-jni releases provide 24 native libraries, each specific to a particular platform, build type, and build flavor.

Six platforms are supported:

• "Linux64" (Linux on x86_64 CPUs)
• "Linux_ARM32hf" (Linux on 32-bit ARM CPUs with hardware floating-point)
• "Linux_ARM64" (Linux on aarch64 CPUs)
• "MacOSX64" (macOS on Intel CPUs)
• "MacOSX_ARM64" (macOS on "Apple Silicon")
• "Windows64" (MS Windows on x86_64 CPUs)

For each platform, 4 native libraries are distributed:

• "ReleaseSp", a release build using single-precision location vectors
• "ReleaseDp", a release build using double-precision location vectors
• "DebugSp", a debug build using single-precision location vectors
• "DebugSp", a debug build using double-precision location vectors

In the following buildscript excerpts:

• "Linux64" may be replaced by another platform.
• "DebugSp" may be replaced by another build type/flavor combination.

Gradle-built projects

Add to the project’s "build.gradle" file:

repositories {
    mavenCentral()
}
dependencies {
    implementation("com.github.stephengold:kk-physics:0.3.0")
    runtimeOnly("com.github.stephengold:jolt-jni-Linux64:0.5.0:DebugSp")
}

For some older versions of Gradle, it's necessary to replace implementation with compile.

Maven-built projects

Add to the project’s "pom.xml" file:

<repositories>
  <repository>
    <id>mvnrepository</id>
    <url>https://repo1.maven.org/maven2/</url>
  </repository>
</repositories>

<dependency>
  <groupId>com.github.stephengold</groupId>
  <artifactId>kk-physics</artifactId>
  <version>0.3.0</version>
</dependency>
<dependency>
  <groupId>com.github.stephengold</groupId>
  <artifactId>jolt-jni-Linux64</artifactId>
  <version>0.5.0</version>
  <classifier>DebugSp</classifier>
</dependency>

How to build KK Physics from source

1. Install a Java Development Kit (JDK), if you don't already have one.
2. Point the JAVA_HOME environment variable to your JDK installation: (In other words, set it to the path of a directory/folder containing a "bin" that contains a Java executable. That path might look something like "C:\Program Files\Eclipse Adoptium\jdk-17.0.3.7-hotspot" or "/usr/lib/jvm/java-17-openjdk-amd64/" or "/Library/Java/JavaVirtualMachines/zulu-17.jdk/Contents/Home" .)

• using Bash or Zsh: export JAVA_HOME=" path to installation "
• using Fish: set -g JAVA_HOME " path to installation "
• using Windows Command Prompt: set JAVA_HOME=" path to installation "
• using PowerShell: $env:JAVA_HOME = ' path to installation '

3. Download and extract the KK Physics source code from GitHub:

• using Git:
  • git clone https://github.com/stephengold/kk-physics.git
  • cd kk-physics
  • git checkout -b latest 0.3.0

4. Run the Gradle wrapper:

• using Bash or Fish or PowerShell or Zsh: ./gradlew build
• using Windows Command Prompt: .\gradlew build

After a successful build, Maven artifacts will be found in "library/build/libs".

You can install the artifacts to your local Maven repository:

• using Bash or Fish or PowerShell or Zsh: ./gradlew install
• using Windows Command Prompt: .\gradlew install

You can restore the project to a pristine state:

• using Bash or Fish or PowerShell or Zsh: ./gradlew clean
• using Windows Command Prompt: .\gradlew clean

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External links

• Jolt Physics Multicore Scaling (2022)
• Architecting Jolt Physics (2022), also in a different form here
• Minie, a similar project that integrates Bullet Physics into jMonkeyEngine
• The physics section of the jMonkeyEngine Wiki (2020)
• Alan Chou's game-physics tutorial (2013)

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History

The evolution of this project is chronicled in its release log.

The API and much of the source code is derived from Minie.

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Acknowledgments

Like most projects, the KK Physics Project builds on the work of many who have gone before. I therefore acknowledge the following software developers:

• Jorrit Rouwe (aka "jrouwe") for creating the Jolt Physics Engine
• Normen Hansen (aka "normen") for creating most of the jme3-bullet library (from which the KK Physics API is derived)
• "aecsocket" for creating the JoltJava bindings to the Jolt Physics Engine
• plus the creators of (and contributors to) the following software:
  • the Firefox web browser
  • the Git revision-control system and GitK commit viewer
  • the GitKraken client
  • the Gradle build tool
  • the Java compiler, standard doclet, and runtime environment
  • jMonkeyEngine and the jME3 Software Development Kit
  • the Jolt Physics Engine
  • the Linux Mint operating system
  • LWJGL, the Lightweight Java Game Library
  • the Markdown document-conversion tool
  • the Meld visual merge tool
  • Microsoft Windows
  • the NetBeans integrated development environment

I am grateful to GitHub and Sonatype for providing free hosting for this project and many other open-source projects.

I'm also grateful to 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: sgold@sonic.net

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