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<h1 class="post-title">PBox2D</h1>
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<p>The PBox2D class is a simple wrapper to help integrate the JBox2D world with ruby implementations of processing (<em>JRubyArt and propane</em>). Use the [WorldBuilder][world_builder] in your sketch setup to create an instance of this class.</p>
<div class="language-ruby highlighter-rouge"><pre class="highlight"><code><span class="c1"># Ruby version of java wrapper allows us to have more</span>
<span class="c1"># rubified interface, also needed for add_listener</span>
<span class="k">class</span> <span class="nc">Box2D</span> <span class="o"><</span> <span class="no">Java</span><span class="o">::</span><span class="no">ProcessingBox2d</span><span class="o">::</span><span class="no">Box2DProcessing</span>
<span class="n">field_accessor</span> <span class="ss">:world</span> <span class="c1"># allow access to protected variable</span>
<span class="k">def</span> <span class="nf">init_options</span><span class="p">(</span><span class="n">args</span> <span class="o">=</span> <span class="p">{})</span>
<span class="n">args</span> <span class="o">=</span> <span class="n">defaults</span><span class="p">.</span><span class="nf">merge</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>
<span class="n">set_options</span><span class="p">(</span><span class="n">args</span><span class="p">[</span><span class="ss">:scale</span><span class="p">],</span>
<span class="n">args</span><span class="p">[</span><span class="ss">:gravity</span><span class="p">].</span><span class="nf">to_java</span><span class="p">(</span><span class="no">Java</span><span class="o">::</span><span class="n">float</span><span class="p">),</span>
<span class="n">args</span><span class="p">[</span><span class="ss">:warm</span><span class="p">],</span>
<span class="n">args</span><span class="p">[</span><span class="ss">:continuous</span><span class="p">]</span>
<span class="p">)</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">step_options</span><span class="p">(</span><span class="n">args</span> <span class="o">=</span> <span class="p">{})</span>
<span class="n">default_step</span><span class="p">.</span><span class="nf">merge</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>
<span class="n">set_step</span><span class="p">(</span><span class="n">args</span><span class="p">[</span><span class="ss">:time_step</span><span class="p">],</span> <span class="n">args</span><span class="p">[</span><span class="ss">:velocity_iter</span><span class="p">],</span> <span class="n">args</span><span class="p">[</span><span class="ss">:position_iter</span><span class="p">])</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">defaults</span>
<span class="p">{</span> <span class="ss">scale: </span><span class="mi">10</span><span class="o">.</span><span class="mi">0</span><span class="p">,</span> <span class="ss">gravity: </span><span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="o">-</span><span class="mi">10</span><span class="p">],</span> <span class="ss">warm: </span><span class="kp">true</span><span class="p">,</span> <span class="ss">continuous: </span><span class="kp">true</span> <span class="p">}</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">default_step</span>
<span class="p">{</span> <span class="ss">time_step: </span><span class="mi">1</span><span class="o">.</span><span class="mi">0</span> <span class="o">/</span> <span class="mi">60</span><span class="p">,</span> <span class="ss">velocity_iter: </span><span class="mi">8</span><span class="p">,</span> <span class="ss">position_iter: </span><span class="mi">10</span> <span class="p">}</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">gravity</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>
<span class="n">change_gravity</span><span class="p">(</span><span class="n">args</span><span class="p">.</span><span class="nf">to_java</span><span class="p">(</span><span class="no">Java</span><span class="o">::</span><span class="n">float</span><span class="p">))</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">add_listener</span><span class="p">(</span><span class="n">listener</span><span class="p">)</span>
<span class="c1"># in combination with field accessor we can access protected world</span>
<span class="n">world</span><span class="p">.</span><span class="nf">setContactListener</span><span class="p">(</span><span class="n">listener</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">version</span>
<span class="nb">format</span><span class="p">(</span><span class="s1">'pbox2d version %s'</span><span class="p">,</span> <span class="no">Pbox2d</span><span class="o">::</span><span class="no">VERSION</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre>
</div>
<p>The java class</p>
<div class="language-java highlighter-rouge"><pre class="highlight"><code>
<span class="kn">package</span> <span class="n">processing</span><span class="o">.</span><span class="na">box2d</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.common.Transform</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.common.Vec2</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.dynamics.Body</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.dynamics.BodyDef</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.dynamics.World</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.dynamics.joints.Joint</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.jbox2d.dynamics.joints.JointDef</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">processing.core.PApplet</span><span class="o">;</span>
<span class="cm">/**
* Loosely based on Box2D-for-processing by Dan Shiffman
*
* @author Martin Prout
*/</span>
<span class="kd">public</span> <span class="kd">abstract</span> <span class="kd">class</span> <span class="nc">Box2DProcessing</span> <span class="o">{</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">PApplet</span> <span class="n">parent</span><span class="o">;</span>
<span class="kd">private</span> <span class="n">Options</span> <span class="n">options</span><span class="o">;</span>
<span class="kd">private</span> <span class="n">Step</span> <span class="n">stepO</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="kt">float</span> <span class="n">height</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="kt">float</span> <span class="n">width</span><span class="o">;</span>
<span class="cm">/**
* The Box2D world (we might need public access for our ContactListener)
*/</span>
<span class="kd">protected</span> <span class="n">World</span> <span class="n">world</span><span class="o">;</span>
<span class="cm">/**
* Scale between processing sketch and physics world
*/</span>
<span class="kd">private</span> <span class="kt">float</span> <span class="n">scaleFactor</span><span class="o">;</span><span class="c1">// = 10.0f;</span>
<span class="cm">/**
* Adjust for processing.org unfathomable choice of y-axis direction
*/</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="kt">float</span> <span class="n">yFlip</span><span class="o">;</span><span class="c1">// = -1.0f; //flip y coordinate</span>
<span class="cm">/**
* Controls access to processing pre loop (via reflection)
*/</span>
<span class="kd">private</span> <span class="kt">boolean</span> <span class="n">isActive</span> <span class="o">=</span> <span class="kc">false</span><span class="o">;</span>
<span class="kd">private</span> <span class="n">Body</span> <span class="n">groundBody</span><span class="o">;</span>
<span class="cm">/**
*
* @param p PApplet
*/</span>
<span class="kd">public</span> <span class="nf">Box2DProcessing</span><span class="o">(</span><span class="n">PApplet</span> <span class="n">p</span><span class="o">)</span> <span class="o">{</span>
<span class="n">parent</span> <span class="o">=</span> <span class="n">p</span><span class="o">;</span>
<span class="n">height</span> <span class="o">=</span> <span class="n">p</span><span class="o">.</span><span class="na">height</span><span class="o">;</span>
<span class="n">width</span> <span class="o">=</span> <span class="n">p</span><span class="o">.</span><span class="na">width</span><span class="o">;</span>
<span class="n">yFlip</span> <span class="o">=</span> <span class="o">-</span><span class="mi">1</span><span class="o">;</span>
<span class="n">setActive</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* Abstract method implement on ruby side
*
* @param listener Custom Listener, Sketch?
*/</span>
<span class="kd">public</span> <span class="kd">abstract</span> <span class="kt">void</span> <span class="nf">addListener</span><span class="o">(</span><span class="n">org</span><span class="o">.</span><span class="na">jbox2d</span><span class="o">.</span><span class="na">callbacks</span><span class="o">.</span><span class="na">ContactListener</span> <span class="n">listener</span><span class="o">);</span>
<span class="cm">/**
*
* @param scale float
* @param gravity float[]
* @param warmStart boolean
* @param continuous boolean
*/</span>
<span class="kd">protected</span> <span class="kt">void</span> <span class="nf">setOptions</span><span class="o">(</span><span class="kt">float</span> <span class="n">scale</span><span class="o">,</span> <span class="kt">float</span><span class="o">[]</span> <span class="n">gravity</span><span class="o">,</span> <span class="kt">boolean</span> <span class="n">warmStart</span><span class="o">,</span> <span class="kt">boolean</span> <span class="n">continuous</span><span class="o">)</span> <span class="o">{</span>
<span class="n">options</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Options</span><span class="o">(</span><span class="n">scale</span><span class="o">,</span> <span class="n">gravity</span><span class="o">,</span> <span class="n">warmStart</span><span class="o">,</span> <span class="n">continuous</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
*
* @param timeStep float
* @param velocity int
* @param position int
*/</span>
<span class="kd">protected</span> <span class="kt">void</span> <span class="nf">setStep</span><span class="o">(</span><span class="kt">float</span> <span class="n">timeStep</span><span class="o">,</span> <span class="kt">int</span> <span class="n">velocity</span><span class="o">,</span> <span class="kt">int</span> <span class="n">position</span><span class="o">)</span> <span class="o">{</span>
<span class="n">stepO</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Step</span><span class="o">(</span><span class="n">timeStep</span><span class="o">,</span> <span class="n">velocity</span><span class="o">,</span> <span class="n">position</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* This is the all important physics "step" function Says to move ahead one
* unit in time Default
*/</span>
<span class="kd">protected</span> <span class="kt">void</span> <span class="nf">step</span><span class="o">()</span> <span class="o">{</span>
<span class="k">if</span> <span class="o">(</span><span class="n">stepO</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
<span class="n">stepO</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Step</span><span class="o">();</span>
<span class="o">}</span>
<span class="n">world</span><span class="o">.</span><span class="na">step</span><span class="o">(</span><span class="n">stepO</span><span class="o">.</span><span class="na">timeStep</span><span class="o">,</span> <span class="n">stepO</span><span class="o">.</span><span class="na">velIters</span><span class="o">,</span> <span class="n">stepO</span><span class="o">.</span><span class="na">posIters</span><span class="o">);</span>
<span class="n">world</span><span class="o">.</span><span class="na">clearForces</span><span class="o">();</span>
<span class="o">}</span>
<span class="cm">/**
* Create a world
*/</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">createWorld</span><span class="o">()</span> <span class="o">{</span>
<span class="k">if</span> <span class="o">(</span><span class="n">options</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
<span class="n">options</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Options</span><span class="o">();</span>
<span class="o">}</span>
<span class="n">Vec2</span> <span class="n">gravity</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Vec2</span><span class="o">(</span><span class="n">options</span><span class="o">.</span><span class="na">gravity</span><span class="o">[</span><span class="mi">0</span><span class="o">],</span> <span class="n">options</span><span class="o">.</span><span class="na">gravity</span><span class="o">[</span><span class="mi">1</span><span class="o">]);</span>
<span class="n">scaleFactor</span> <span class="o">=</span> <span class="n">options</span><span class="o">.</span><span class="na">scaleFactor</span><span class="o">;</span>
<span class="n">world</span> <span class="o">=</span> <span class="k">new</span> <span class="n">World</span><span class="o">(</span><span class="n">gravity</span><span class="o">);</span>
<span class="n">world</span><span class="o">.</span><span class="na">setWarmStarting</span><span class="o">(</span><span class="n">options</span><span class="o">.</span><span class="na">warm</span><span class="o">);</span>
<span class="n">world</span><span class="o">.</span><span class="na">setContinuousPhysics</span><span class="o">(</span><span class="n">options</span><span class="o">.</span><span class="na">continuous</span><span class="o">);</span>
<span class="n">BodyDef</span> <span class="n">bodyDef</span> <span class="o">=</span> <span class="k">new</span> <span class="n">BodyDef</span><span class="o">();</span>
<span class="n">groundBody</span> <span class="o">=</span> <span class="n">world</span><span class="o">.</span><span class="na">createBody</span><span class="o">(</span><span class="n">bodyDef</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
*
* @return Body
*/</span>
<span class="kd">public</span> <span class="n">Body</span> <span class="nf">groundBody</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">groundBody</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
* Set the gravity (this can change in real-time)
*
* @param gravity float[]
*/</span>
<span class="kd">protected</span> <span class="kt">void</span> <span class="nf">changeGravity</span><span class="o">(</span><span class="kt">float</span><span class="o">[]</span> <span class="n">gravity</span><span class="o">)</span> <span class="o">{</span>
<span class="n">world</span><span class="o">.</span><span class="na">setGravity</span><span class="o">(</span><span class="k">new</span> <span class="n">Vec2</span><span class="o">(</span><span class="n">gravity</span><span class="o">[</span><span class="mi">0</span><span class="o">],</span> <span class="n">gravity</span><span class="o">[</span><span class="mi">1</span><span class="o">]));</span>
<span class="o">}</span>
<span class="cm">/**
* Box2d has its own coordinate system and we have to move back and forth
* between them to convert from Box2d world to processing pixel space
*
* @param world Vec2
* @return Vec2
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">worldToProcessing</span><span class="o">(</span><span class="n">Vec2</span> <span class="n">world</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="nf">worldToProcessing</span><span class="o">(</span><span class="n">world</span><span class="o">.</span><span class="na">x</span><span class="o">,</span> <span class="n">world</span><span class="o">.</span><span class="na">y</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* Box2d has its own coordinate system and we have to move back and forth
* between them to convert from Box2d world to processing pixel space
* Note reverse Y mapping (processing poxy coord system again)
* @param worldX float
* @param worldY float
* @return Vec2
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">worldToProcessing</span><span class="o">(</span><span class="kt">float</span> <span class="n">worldX</span><span class="o">,</span> <span class="kt">float</span> <span class="n">worldY</span><span class="o">)</span> <span class="o">{</span>
<span class="kt">float</span> <span class="n">pixelX</span> <span class="o">=</span> <span class="n">map</span><span class="o">(</span><span class="n">worldX</span><span class="o">,</span> <span class="mi">0</span><span class="n">f</span><span class="o">,</span> <span class="mi">1</span><span class="n">f</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">width</span> <span class="o">/</span> <span class="mi">2</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">width</span> <span class="o">/</span> <span class="mi">2</span> <span class="o">+</span> <span class="n">scaleFactor</span><span class="o">);</span>
<span class="kt">float</span> <span class="n">pixelY</span> <span class="o">=</span> <span class="n">map</span><span class="o">(</span><span class="n">worldY</span><span class="o">,</span> <span class="mi">1</span><span class="n">f</span><span class="o">,</span> <span class="mi">0</span><span class="n">f</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">height</span> <span class="o">/</span> <span class="mi">2</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">height</span> <span class="o">/</span> <span class="mi">2</span> <span class="o">+</span> <span class="n">scaleFactor</span><span class="o">);</span>
<span class="k">return</span> <span class="k">new</span> <span class="nf">Vec2</span><span class="o">(</span><span class="n">pixelX</span><span class="o">,</span> <span class="n">pixelY</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* convert Coordinate from pixel space to box2d world
*
* @param screen Vec2
* @return Vec2
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">processingToWorld</span><span class="o">(</span><span class="n">Vec2</span> <span class="n">screen</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="nf">processingToWorld</span><span class="o">(</span><span class="n">screen</span><span class="o">.</span><span class="na">x</span><span class="o">,</span> <span class="n">screen</span><span class="o">.</span><span class="na">y</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* Note reverse Y mapping (processing poxy coord system again)
* @param pixelX float
* @param pixelY float
* @return Vec2
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">processingToWorld</span><span class="o">(</span><span class="kt">float</span> <span class="n">pixelX</span><span class="o">,</span> <span class="kt">float</span> <span class="n">pixelY</span><span class="o">)</span> <span class="o">{</span>
<span class="kt">float</span> <span class="n">worldX</span> <span class="o">=</span> <span class="n">map</span><span class="o">(</span><span class="n">pixelX</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">width</span> <span class="o">/</span> <span class="mi">2</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">width</span> <span class="o">/</span> <span class="mi">2</span> <span class="o">+</span> <span class="n">scaleFactor</span><span class="o">,</span> <span class="mi">0</span><span class="n">f</span><span class="o">,</span> <span class="mi">1</span><span class="n">f</span><span class="o">);</span>
<span class="kt">float</span> <span class="n">worldY</span> <span class="o">=</span> <span class="n">map</span><span class="o">(</span><span class="n">pixelY</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">height</span> <span class="o">/</span> <span class="mi">2</span><span class="o">,</span> <span class="n">parent</span><span class="o">.</span><span class="na">height</span> <span class="o">/</span> <span class="mi">2</span> <span class="o">+</span> <span class="n">scaleFactor</span><span class="o">,</span> <span class="mi">1</span><span class="n">f</span><span class="o">,</span> <span class="mi">0</span><span class="n">f</span><span class="o">);</span>
<span class="k">return</span> <span class="k">new</span> <span class="nf">Vec2</span><span class="o">(</span><span class="n">worldX</span><span class="o">,</span> <span class="n">worldY</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* Scale from processing to world
*
* @param val float
* @return float
*/</span>
<span class="kd">public</span> <span class="kt">float</span> <span class="nf">scaleToWorld</span><span class="o">(</span><span class="kt">float</span> <span class="n">val</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">val</span> <span class="o">/</span> <span class="n">scaleFactor</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
* Scale from world to processing
*
* @param val float
* @return float
*/</span>
<span class="kd">public</span> <span class="kt">float</span> <span class="nf">scaleToProcessing</span><span class="o">(</span><span class="kt">float</span> <span class="n">val</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">val</span> <span class="o">*</span> <span class="n">scaleFactor</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
* Vector scale between two worlds
*
* @param v Vec2
* @return Vec2
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">vectorToWorld</span><span class="o">(</span><span class="n">Vec2</span> <span class="n">v</span><span class="o">)</span> <span class="o">{</span>
<span class="n">Vec2</span> <span class="n">u</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Vec2</span><span class="o">(</span><span class="n">v</span><span class="o">.</span><span class="na">x</span> <span class="o">/</span> <span class="n">scaleFactor</span><span class="o">,</span> <span class="n">v</span><span class="o">.</span><span class="na">y</span> <span class="o">/</span> <span class="n">scaleFactor</span><span class="o">);</span>
<span class="n">u</span><span class="o">.</span><span class="na">y</span> <span class="o">*=</span> <span class="n">yFlip</span><span class="o">;</span>
<span class="k">return</span> <span class="n">u</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
* Translate from world coords to processing as a Vec2
*
* @param x float
* @param y float
* @return Vec
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">vectorToWorld</span><span class="o">(</span><span class="kt">float</span> <span class="n">x</span><span class="o">,</span> <span class="kt">float</span> <span class="n">y</span><span class="o">)</span> <span class="o">{</span>
<span class="n">Vec2</span> <span class="n">u</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Vec2</span><span class="o">(</span><span class="n">x</span> <span class="o">/</span> <span class="n">scaleFactor</span><span class="o">,</span> <span class="n">y</span> <span class="o">/</span> <span class="n">scaleFactor</span><span class="o">);</span>
<span class="n">u</span><span class="o">.</span><span class="na">y</span> <span class="o">*=</span> <span class="n">yFlip</span><span class="o">;</span>
<span class="k">return</span> <span class="n">u</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
* Translate from world to processing as a Vec2
*
* @param v Vec
* @return Vec
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">vectorToProcessing</span><span class="o">(</span><span class="n">Vec2</span> <span class="n">v</span><span class="o">)</span> <span class="o">{</span>
<span class="n">Vec2</span> <span class="n">u</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Vec2</span><span class="o">(</span><span class="n">v</span><span class="o">.</span><span class="na">x</span> <span class="o">*</span> <span class="n">scaleFactor</span><span class="o">,</span> <span class="n">v</span><span class="o">.</span><span class="na">y</span> <span class="o">*</span> <span class="n">scaleFactor</span><span class="o">);</span>
<span class="n">u</span><span class="o">.</span><span class="na">y</span> <span class="o">*=</span> <span class="n">yFlip</span><span class="o">;</span>
<span class="k">return</span> <span class="n">u</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
* A common task we have to do a lot
*
* @param bd BodyDef
* @return Body
*/</span>
<span class="kd">public</span> <span class="n">Body</span> <span class="nf">createBody</span><span class="o">(</span><span class="n">BodyDef</span> <span class="n">bd</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">world</span><span class="o">.</span><span class="na">createBody</span><span class="o">(</span><span class="n">bd</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* A common task we have to do a lot
*
* @param jd JointDef
* @return World
*/</span>
<span class="kd">public</span> <span class="n">Joint</span> <span class="nf">createJoint</span><span class="o">(</span><span class="n">JointDef</span> <span class="n">jd</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">world</span><span class="o">.</span><span class="na">createJoint</span><span class="o">(</span><span class="n">jd</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
*
* @param b Body
* @return body coord as Vec2
*/</span>
<span class="kd">public</span> <span class="n">Vec2</span> <span class="nf">bodyCoord</span><span class="o">(</span><span class="n">Body</span> <span class="n">b</span><span class="o">)</span> <span class="o">{</span>
<span class="n">Transform</span> <span class="n">xf</span> <span class="o">=</span> <span class="n">b</span><span class="o">.</span><span class="na">getTransform</span><span class="o">();</span>
<span class="k">return</span> <span class="nf">worldToProcessing</span><span class="o">(</span><span class="n">xf</span><span class="o">.</span><span class="na">p</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
*
* @param b Body
*/</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">destroyBody</span><span class="o">(</span><span class="n">Body</span> <span class="n">b</span><span class="o">)</span> <span class="o">{</span>
<span class="n">world</span><span class="o">.</span><span class="na">destroyBody</span><span class="o">(</span><span class="n">b</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
* Access the processing pre loop by java reflection
*/</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">pre</span><span class="o">()</span> <span class="o">{</span>
<span class="n">step</span><span class="o">();</span>
<span class="o">}</span>
<span class="cm">/**
* Recommended inclusion in a processing library
*/</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">dispose</span><span class="o">()</span> <span class="o">{</span>
<span class="n">setActive</span><span class="o">(</span><span class="kc">false</span><span class="o">);</span>
<span class="o">}</span>
<span class="cm">/**
*
* @return height float
*/</span>
<span class="kd">public</span> <span class="kt">float</span> <span class="nf">height</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">height</span><span class="o">;</span>
<span class="o">}</span>
<span class="cm">/**
*
* @return width float
*/</span>
<span class="kd">public</span> <span class="kt">float</span> <span class="nf">width</span><span class="o">()</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">width</span><span class="o">;</span>
<span class="o">}</span>
<span class="kd">private</span> <span class="kt">float</span> <span class="nf">map</span><span class="o">(</span><span class="kt">float</span> <span class="n">val</span><span class="o">,</span> <span class="kt">float</span> <span class="n">startIn</span><span class="o">,</span> <span class="kt">float</span> <span class="n">endIn</span><span class="o">,</span> <span class="kt">float</span> <span class="n">startOut</span><span class="o">,</span> <span class="kt">float</span> <span class="n">endOut</span><span class="o">)</span> <span class="o">{</span>
<span class="k">return</span> <span class="n">startOut</span> <span class="o">+</span> <span class="o">(</span><span class="n">endOut</span> <span class="o">-</span> <span class="n">startOut</span><span class="o">)</span> <span class="o">*</span> <span class="o">((</span><span class="n">val</span> <span class="o">-</span> <span class="n">startIn</span><span class="o">)</span> <span class="o">/</span> <span class="o">(</span><span class="n">endIn</span> <span class="o">-</span> <span class="n">startIn</span><span class="o">));</span>
<span class="o">}</span>
<span class="kd">private</span> <span class="kt">void</span> <span class="nf">setActive</span><span class="o">(</span><span class="kt">boolean</span> <span class="n">active</span><span class="o">)</span> <span class="o">{</span>
<span class="k">if</span> <span class="o">(</span><span class="n">active</span> <span class="o">!=</span> <span class="n">isActive</span><span class="o">)</span> <span class="o">{</span>
<span class="n">isActive</span> <span class="o">=</span> <span class="n">active</span><span class="o">;</span>
<span class="k">if</span> <span class="o">(</span><span class="n">active</span><span class="o">)</span> <span class="o">{</span>
<span class="n">parent</span><span class="o">.</span><span class="na">registerMethod</span><span class="o">(</span><span class="s">"dispose"</span><span class="o">,</span> <span class="k">this</span><span class="o">);</span>
<span class="n">parent</span><span class="o">.</span><span class="na">registerMethod</span><span class="o">(</span><span class="s">"pre"</span><span class="o">,</span> <span class="k">this</span><span class="o">);</span>
<span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
<span class="n">parent</span><span class="o">.</span><span class="na">unregisterMethod</span><span class="o">(</span><span class="s">"pre"</span><span class="o">,</span> <span class="k">this</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre>
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<h2 class="footer-heading">PBox2D for JRubyArt</h2>
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