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              <h1 id="demo-delaunator-001">Demo Delaunator 001</h1>
<p>Delauney triangulation and Voronoi cell visualisation</p>

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              <p><a href="../../demo/delaunator-001.html">Run code</a></p>

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            <div class="content"><div class='highlight'><pre>
<span class="hljs-comment">/** <span class="hljs-doctag">@ts</span>-expect-error */</span>
<span class="hljs-keyword">import</span> <span class="hljs-title class_">Delaunator</span> <span class="hljs-keyword">from</span> <span class="hljs-string">&#x27;https://cdn.skypack.dev/delaunator@5.0.0&#x27;</span>;</pre></div></div>
            
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              <p>The following functions are used to handle the Delaunay object</p>
<ul>
<li>Code adapted from the <a href="https://mapbox.github.io/delaunator/">Delaunator Guide website</a></li>
</ul>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> <span class="hljs-title function_">edgesOfTriangle</span> = (<span class="hljs-params">t</span>) =&gt; [<span class="hljs-number">3</span> * t, <span class="hljs-number">3</span> * t + <span class="hljs-number">1</span>, <span class="hljs-number">3</span> * t + <span class="hljs-number">2</span>];

<span class="hljs-keyword">const</span> <span class="hljs-title function_">pointsOfTriangle</span> = (<span class="hljs-params">del, t</span>) =&gt; {

    <span class="hljs-keyword">const</span> { triangles } = del;

    <span class="hljs-keyword">return</span> <span class="hljs-title function_">edgesOfTriangle</span>(t).<span class="hljs-title function_">map</span>(<span class="hljs-function"><span class="hljs-params">e</span> =&gt;</span> triangles[e]);
};

<span class="hljs-keyword">const</span> <span class="hljs-title function_">triangleOfEdge</span> = (<span class="hljs-params">e</span>) =&gt; <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">floor</span>(e / <span class="hljs-number">3</span>);

<span class="hljs-keyword">const</span> <span class="hljs-title function_">nextHalfedge</span> = (<span class="hljs-params">e</span>) =&gt; (e % <span class="hljs-number">3</span> === <span class="hljs-number">2</span>) ? e - <span class="hljs-number">2</span> : e + <span class="hljs-number">1</span>;

<span class="hljs-keyword">const</span> <span class="hljs-title function_">forEachTriangleEdge</span> = (<span class="hljs-params">pts, del, cb</span>) =&gt; {

    <span class="hljs-keyword">const</span> { triangles, halfedges } = del;

    <span class="hljs-keyword">const</span> len = triangles.<span class="hljs-property">length</span>;

    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> e = <span class="hljs-number">0</span>; e &lt; len; e++) {

        <span class="hljs-keyword">if</span> (e &gt; halfedges[e]) {

            <span class="hljs-keyword">const</span> p = pts[triangles[e]];
            <span class="hljs-keyword">const</span> q = pts[triangles[<span class="hljs-title function_">nextHalfedge</span>(e)]];

            <span class="hljs-title function_">cb</span>(e, p, q);
        }
    }
};

<span class="hljs-keyword">const</span> <span class="hljs-title function_">triangleCenter</span> = (<span class="hljs-params">pts, del, t</span>) =&gt; {

    <span class="hljs-keyword">const</span> vertices = <span class="hljs-title function_">pointsOfTriangle</span>(del, t).<span class="hljs-title function_">map</span>(<span class="hljs-function"><span class="hljs-params">p</span> =&gt;</span> pts[p]);

    <span class="hljs-keyword">return</span> <span class="hljs-title function_">circumcenter</span>(vertices[<span class="hljs-number">0</span>], vertices[<span class="hljs-number">1</span>], vertices[<span class="hljs-number">2</span>]);
};

<span class="hljs-keyword">const</span> <span class="hljs-title function_">circumcenter</span> = (<span class="hljs-params">a, b, c</span>) =&gt; {

    <span class="hljs-keyword">if</span> (a &amp;&amp; b &amp;&amp; c &amp;&amp; a.<span class="hljs-property">length</span> &amp;&amp; b.<span class="hljs-property">length</span> &amp;&amp; c.<span class="hljs-property">length</span>) {

        <span class="hljs-keyword">const</span> ad = a[<span class="hljs-number">0</span>] * a[<span class="hljs-number">0</span>] + a[<span class="hljs-number">1</span>] * a[<span class="hljs-number">1</span>],
            bd = b[<span class="hljs-number">0</span>] * b[<span class="hljs-number">0</span>] + b[<span class="hljs-number">1</span>] * b[<span class="hljs-number">1</span>],
            cd = c[<span class="hljs-number">0</span>] * c[<span class="hljs-number">0</span>] + c[<span class="hljs-number">1</span>] * c[<span class="hljs-number">1</span>];

        <span class="hljs-keyword">const</span> D = <span class="hljs-number">2</span> * (a[<span class="hljs-number">0</span>] * (b[<span class="hljs-number">1</span>] - c[<span class="hljs-number">1</span>]) + b[<span class="hljs-number">0</span>] * (c[<span class="hljs-number">1</span>] - a[<span class="hljs-number">1</span>]) + c[<span class="hljs-number">0</span>] * (a[<span class="hljs-number">1</span>] - b[<span class="hljs-number">1</span>]));

        <span class="hljs-keyword">return</span> [
            <span class="hljs-number">1</span> / D * (ad * (b[<span class="hljs-number">1</span>] - c[<span class="hljs-number">1</span>]) + bd * (c[<span class="hljs-number">1</span>] - a[<span class="hljs-number">1</span>]) + cd * (a[<span class="hljs-number">1</span>] - b[<span class="hljs-number">1</span>])),
            <span class="hljs-number">1</span> / D * (ad * (c[<span class="hljs-number">0</span>] - b[<span class="hljs-number">0</span>]) + bd * (a[<span class="hljs-number">0</span>] - c[<span class="hljs-number">0</span>]) + cd * (b[<span class="hljs-number">0</span>] - a[<span class="hljs-number">0</span>])),
        ];
    }
};

<span class="hljs-keyword">const</span> <span class="hljs-title function_">forEachVoronoiEdge</span> = (<span class="hljs-params">pts, del, cb</span>) =&gt; {

    <span class="hljs-keyword">if</span> (del) {

        <span class="hljs-keyword">const</span> { triangles, halfedges } = del;

        <span class="hljs-keyword">const</span> len = triangles.<span class="hljs-property">length</span>;

        <span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> e = <span class="hljs-number">0</span>; e &lt; len; e++) {

            <span class="hljs-keyword">if</span> (e &lt; halfedges[e]) {

                <span class="hljs-keyword">const</span> p = <span class="hljs-title function_">triangleCenter</span>(pts, del, <span class="hljs-title function_">triangleOfEdge</span>(e));
                <span class="hljs-keyword">const</span> q = <span class="hljs-title function_">triangleCenter</span>(pts, del, <span class="hljs-title function_">triangleOfEdge</span>(halfedges[e]));

                <span class="hljs-title function_">cb</span>(e, p, q);
            }
        }
    }
};</pre></div></div>
            
        </li>
        
        
        <li id="section-4">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-4">&#x00a7;</a>
              </div>
              <h4 id="scene-setup">Scene setup</h4>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-keyword">import</span> * <span class="hljs-keyword">as</span> scrawl <span class="hljs-keyword">from</span> <span class="hljs-string">&#x27;../source/scrawl.js&#x27;</span>;

<span class="hljs-keyword">import</span> { reportSpeed } <span class="hljs-keyword">from</span> <span class="hljs-string">&#x27;./utilities.js&#x27;</span>;

<span class="hljs-keyword">const</span> canvas = scrawl.<span class="hljs-title function_">findCanvas</span>(<span class="hljs-string">&#x27;mycanvas&#x27;</span>);</pre></div></div>
            
        </li>
        
        
        <li id="section-5">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-5">&#x00a7;</a>
              </div>
              <p>Namespacing boilerplate</p>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> namespace = canvas.<span class="hljs-property">name</span>;
<span class="hljs-keyword">const</span> <span class="hljs-title function_">name</span> = (<span class="hljs-params">n</span>) =&gt; <span class="hljs-string">`<span class="hljs-subst">${namespace}</span>-<span class="hljs-subst">${n}</span>`</span>;</pre></div></div>
            
        </li>
        
        
        <li id="section-6">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-6">&#x00a7;</a>
              </div>
              <p>Create a Block entity which covers the entire canvas; this will act as the area in which particles will be generated by the Emitter entity</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>scrawl.<span class="hljs-title function_">makeBlock</span>({

    <span class="hljs-attr">name</span>: <span class="hljs-title function_">name</span>(<span class="hljs-string">&#x27;field-block&#x27;</span>),
    <span class="hljs-attr">order</span>: <span class="hljs-number">1</span>,
    <span class="hljs-attr">dimensions</span>: [<span class="hljs-string">&#x27;100%&#x27;</span>, <span class="hljs-string">&#x27;100%&#x27;</span>],
    <span class="hljs-attr">method</span>: <span class="hljs-string">&#x27;none&#x27;</span>,
});


scrawl.<span class="hljs-title function_">makeWheel</span>({

    <span class="hljs-attr">name</span>: <span class="hljs-title function_">name</span>(<span class="hljs-string">&#x27;mouse-planet&#x27;</span>),
    <span class="hljs-attr">radius</span>: <span class="hljs-number">12</span>,
    <span class="hljs-attr">handle</span>: [<span class="hljs-string">&#x27;center&#x27;</span>, <span class="hljs-string">&#x27;center&#x27;</span>],
    <span class="hljs-attr">fillStyle</span>: <span class="hljs-string">&#x27;gold&#x27;</span>,
    <span class="hljs-attr">lockTo</span>: <span class="hljs-string">&#x27;mouse&#x27;</span>,
});</pre></div></div>
            
        </li>
        
        
        <li id="section-7">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-7">&#x00a7;</a>
              </div>
              <h4 id="particle-physics-animation-scene">Particle physics animation scene</h4>

            </div>
            
        </li>
        
        
        <li id="section-8">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-8">&#x00a7;</a>
              </div>
              <p>Create a World object which we can then assign to the particle emitter</p>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> myWorld = scrawl.<span class="hljs-title function_">makeWorld</span>({

    <span class="hljs-attr">name</span>: <span class="hljs-title function_">name</span>(<span class="hljs-string">&#x27;my-world&#x27;</span>),
    <span class="hljs-attr">tickMultiplier</span>: <span class="hljs-number">2</span>,

    <span class="hljs-attr">userAttributes</span>: [
        {
            <span class="hljs-attr">key</span>: <span class="hljs-string">&#x27;coords&#x27;</span>,
            <span class="hljs-attr">defaultValue</span>: [],
<span class="hljs-comment">/** <span class="hljs-doctag">@ts</span>-expect-error */</span>
            <span class="hljs-attr">getter</span>: <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) { <span class="hljs-keyword">return</span> [].<span class="hljs-title function_">concat</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">coords</span>) },
            <span class="hljs-attr">setter</span>: <span class="hljs-keyword">function</span> (<span class="hljs-params">emitter</span>) {

<span class="hljs-comment">/** <span class="hljs-doctag">@ts</span>-expect-error */</span>
                <span class="hljs-keyword">const</span> { coords } = <span class="hljs-variable language_">this</span>;
                coords.<span class="hljs-property">length</span> = <span class="hljs-number">0</span>;

                <span class="hljs-keyword">const</span> { particleStore } = emitter;

                particleStore.<span class="hljs-title function_">forEach</span>(<span class="hljs-function"><span class="hljs-params">p</span> =&gt;</span> {

                    <span class="hljs-keyword">const</span> pos = p.<span class="hljs-property">position</span>;

                    coords.<span class="hljs-title function_">push</span>([pos.<span class="hljs-property">x</span>, pos.<span class="hljs-property">y</span>]);
                });

                <span class="hljs-keyword">const</span> here = (canvas) ? canvas.<span class="hljs-property">here</span> : <span class="hljs-literal">false</span>;

                <span class="hljs-keyword">if</span> (here &amp;&amp; here.<span class="hljs-property">active</span>) coords.<span class="hljs-title function_">push</span>([here.<span class="hljs-property">x</span>, here.<span class="hljs-property">y</span>]);
            },
        },
    ],
});

<span class="hljs-keyword">let</span> delaunay = <span class="hljs-literal">false</span>;

<span class="hljs-keyword">const</span> buildDelaunayObject = <span class="hljs-keyword">function</span> (<span class="hljs-params">coords</span>) {

    <span class="hljs-keyword">return</span> <span class="hljs-title class_">Delaunator</span>.<span class="hljs-title function_">from</span>(coords);
};

scrawl.<span class="hljs-title function_">makeEmitter</span>({

    <span class="hljs-attr">name</span>: <span class="hljs-title function_">name</span>(<span class="hljs-string">&#x27;field-emitter&#x27;</span>),
    <span class="hljs-attr">world</span>: myWorld,

    <span class="hljs-attr">generationRate</span>: <span class="hljs-number">5</span>,

    <span class="hljs-attr">particleCount</span>: <span class="hljs-number">80</span>,
    <span class="hljs-attr">start</span>: [<span class="hljs-string">&#x27;center&#x27;</span>, <span class="hljs-string">&#x27;center&#x27;</span>],

    <span class="hljs-attr">killRadius</span>: <span class="hljs-number">500</span>,
    <span class="hljs-attr">killRadiusVariation</span>: <span class="hljs-number">0</span>,

    <span class="hljs-attr">rangeX</span>: <span class="hljs-number">24</span>,
    <span class="hljs-attr">rangeFromX</span>: -<span class="hljs-number">12</span>,
    <span class="hljs-attr">rangeY</span>: <span class="hljs-number">24</span>,
    <span class="hljs-attr">rangeFromY</span>: -<span class="hljs-number">12</span>,

    <span class="hljs-attr">artefact</span>: scrawl.<span class="hljs-title function_">makeStar</span>({

        <span class="hljs-attr">name</span>: <span class="hljs-title function_">name</span>(<span class="hljs-string">&#x27;particle-star-entity&#x27;</span>),

        <span class="hljs-attr">radius1</span>: <span class="hljs-number">8</span>,
        <span class="hljs-attr">radius2</span>: <span class="hljs-number">5</span>,

        <span class="hljs-attr">points</span>: <span class="hljs-number">5</span>,

        <span class="hljs-attr">handle</span>: [<span class="hljs-string">&#x27;center&#x27;</span>, <span class="hljs-string">&#x27;center&#x27;</span>],

        <span class="hljs-attr">fillStyle</span>: <span class="hljs-string">&#x27;aliceblue&#x27;</span>,
        <span class="hljs-attr">strokeStyle</span>: <span class="hljs-string">&#x27;orange&#x27;</span>,
        <span class="hljs-attr">method</span>: <span class="hljs-string">&#x27;fillThenDraw&#x27;</span>,

        <span class="hljs-attr">visibility</span>: <span class="hljs-literal">false</span>,

        <span class="hljs-attr">noUserInteraction</span>: <span class="hljs-literal">true</span>,
        <span class="hljs-attr">noPositionDependencies</span>: <span class="hljs-literal">true</span>,
        <span class="hljs-attr">noFilters</span>: <span class="hljs-literal">true</span>,
        <span class="hljs-attr">noDeltaUpdates</span>: <span class="hljs-literal">true</span>,
    }),

    <span class="hljs-attr">preAction</span>: <span class="hljs-keyword">function</span> (<span class="hljs-params">host</span>) {</pre></div></div>
            
        </li>
        
        
        <li id="section-9">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-9">&#x00a7;</a>
              </div>
              <p>generate coords</p>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-comment">/** <span class="hljs-doctag">@ts</span>-expect-error */</span>
        <span class="hljs-variable language_">this</span>.<span class="hljs-property">world</span>.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">coords</span>: <span class="hljs-variable language_">this</span> });

<span class="hljs-comment">/** <span class="hljs-doctag">@ts</span>-expect-error */</span>
        <span class="hljs-keyword">const</span> c = <span class="hljs-variable language_">this</span>.<span class="hljs-property">world</span>.<span class="hljs-title function_">get</span>(<span class="hljs-string">&#x27;coords&#x27;</span>);</pre></div></div>
            
        </li>
        
        
        <li id="section-10">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-10">&#x00a7;</a>
              </div>
              <p>Build a new Delaunay object for each iteration (think of this as a stress test)</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        <span class="hljs-keyword">if</span> (c.<span class="hljs-property">length</span>) delaunay = <span class="hljs-title function_">buildDelaunayObject</span>(c);

        <span class="hljs-keyword">if</span> (delaunay) {

            <span class="hljs-keyword">const</span> engine = host.<span class="hljs-property">engine</span>;

            engine.<span class="hljs-title function_">save</span>();

            engine.<span class="hljs-title function_">setTransform</span>(<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>);

            engine.<span class="hljs-property">lineWidth</span> = <span class="hljs-number">3</span>;
            engine.<span class="hljs-property">strokeStyle</span> = <span class="hljs-string">&#x27;gold&#x27;</span>;
            engine.<span class="hljs-property">globalAlpha</span> = <span class="hljs-number">0.4</span>;

            engine.<span class="hljs-title function_">beginPath</span>();

            <span class="hljs-title function_">forEachTriangleEdge</span>(c, delaunay, <span class="hljs-function">(<span class="hljs-params">e, p, q</span>) =&gt;</span> {

                <span class="hljs-keyword">if</span> (p &amp;&amp; q) {

                    engine.<span class="hljs-title function_">moveTo</span>(...p);
                    engine.<span class="hljs-title function_">lineTo</span>(...q);
                }
            });

            engine.<span class="hljs-title function_">stroke</span>();

            engine.<span class="hljs-property">strokeStyle</span> = <span class="hljs-string">&#x27;lightgreen&#x27;</span>;
            engine.<span class="hljs-property">globalAlpha</span> = <span class="hljs-number">1</span>;

            engine.<span class="hljs-title function_">beginPath</span>();

            <span class="hljs-title function_">forEachVoronoiEdge</span>(c, delaunay, <span class="hljs-function">(<span class="hljs-params">e, p, q</span>) =&gt;</span> {

                <span class="hljs-keyword">if</span> (p &amp;&amp; q) {

                    engine.<span class="hljs-title function_">moveTo</span>(...p);
                    engine.<span class="hljs-title function_">lineTo</span>(...q);
                }
            });

            engine.<span class="hljs-title function_">stroke</span>();

            engine.<span class="hljs-title function_">restore</span>();
        }
    },</pre></div></div>
            
        </li>
        
        
        <li id="section-11">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-11">&#x00a7;</a>
              </div>
              <p>The <code>stampAction</code> function just adds the stars to the scene</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-attr">stampAction</span>: <span class="hljs-keyword">function</span> (<span class="hljs-params">artefact, particle, host</span>) {

        <span class="hljs-keyword">const</span> [, , ...start] = particle.<span class="hljs-property">history</span>[<span class="hljs-number">0</span>];
        artefact.<span class="hljs-title function_">simpleStamp</span>(host, {start});
    },
});</pre></div></div>
            
        </li>
        
        
        <li id="section-12">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-12">&#x00a7;</a>
              </div>
              <h4 id="user-interaction">User interaction</h4>
<p>For this demo we will suppress touchmove functionality over the canvas</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>scrawl.<span class="hljs-title function_">addNativeListener</span>([<span class="hljs-string">&#x27;touchmove&#x27;</span>], <span class="hljs-function">(<span class="hljs-params">e</span>) =&gt;</span> {

    e.<span class="hljs-title function_">preventDefault</span>();
    e.<span class="hljs-property">returnValue</span> = <span class="hljs-literal">false</span>;

}, canvas.<span class="hljs-property">domElement</span>);</pre></div></div>
            
        </li>
        
        
        <li id="section-13">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-13">&#x00a7;</a>
              </div>
              <h4 id="scene-animation">Scene animation</h4>
<p>Function to display frames-per-second data, and other information relevant to the demo</p>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> report = <span class="hljs-title function_">reportSpeed</span>(<span class="hljs-string">&#x27;#reportmessage&#x27;</span>);</pre></div></div>
            
        </li>
        
        
        <li id="section-14">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-14">&#x00a7;</a>
              </div>
              <p>Create the Display cycle animation</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>scrawl.<span class="hljs-title function_">makeRender</span>({

    <span class="hljs-attr">name</span>: <span class="hljs-title function_">name</span>(<span class="hljs-string">&#x27;animation&#x27;</span>),
    <span class="hljs-attr">target</span>: canvas,
    <span class="hljs-attr">afterShow</span>: report,
});</pre></div></div>
            
        </li>
        
        
        <li id="section-15">
            <div class="annotation">
              
              <div class="sswrap ">
                <a class="ss" href="#section-15">&#x00a7;</a>
              </div>
              <h4 id="development-and-testing">Development and testing</h4>

            </div>
            
            <div class="content"><div class='highlight'><pre><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(scrawl.<span class="hljs-property">library</span>);</pre></div></div>
            
        </li>
        
    </ul>
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