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api.html
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<!doctype html>
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<section>
<h1>Embree API Example</h1>
<p>
On this page you find a
simple example application (a Embree 'hello world', if you will), to
demonstrate how easy it is to use Embree. The application creates a
triangle and a ray and performs a ray-triangle intersection using the
Embree API. The full source code is shown below and afterwards small
snippets of the code will be discussed in more detail. Build instructions
can be found at the bottom of the page. Please refer to the documentation
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<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
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<span class="normal">49</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="c1">// Copyright 2009-2021 Intel Corporation</span>
<span class="c1">// SPDX-License-Identifier: Apache-2.0</span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf"><embree3/rtcore.h></span><span class="cp"></span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf"><limits></span><span class="cp"></span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf"><iostream></span><span class="cp"></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"></span>
<span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">RTCDevice</span><span class="w"> </span><span class="n">device</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rtcNewDevice</span><span class="p">(</span><span class="nb">NULL</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">RTCScene</span><span class="w"> </span><span class="n">scene</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rtcNewScene</span><span class="p">(</span><span class="n">device</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">RTCGeometry</span><span class="w"> </span><span class="n">geom</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rtcNewGeometry</span><span class="p">(</span><span class="n">device</span><span class="p">,</span><span class="w"> </span><span class="n">RTC_GEOMETRY_TYPE_TRIANGLE</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="kt">float</span><span class="o">*</span><span class="w"> </span><span class="n">vb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="o">*</span><span class="p">)</span><span class="w"> </span><span class="n">rtcSetNewGeometryBuffer</span><span class="p">(</span><span class="n">geom</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">RTC_BUFFER_TYPE_VERTEX</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">RTC_FORMAT_FLOAT3</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="o">*</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">float</span><span class="p">),</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="c1">// 1st vertex</span>
<span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="c1">// 2nd vertex</span>
<span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">8</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="c1">// 3rd vertex</span>
<span class="w"> </span><span class="kt">unsigned</span><span class="o">*</span><span class="w"> </span><span class="n">ib</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">unsigned</span><span class="o">*</span><span class="p">)</span><span class="w"> </span><span class="n">rtcSetNewGeometryBuffer</span><span class="p">(</span><span class="n">geom</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">RTC_BUFFER_TYPE_INDEX</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">RTC_FORMAT_UINT3</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="o">*</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">unsigned</span><span class="p">),</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">ib</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">ib</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">ib</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcCommitGeometry</span><span class="p">(</span><span class="n">geom</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcAttachGeometry</span><span class="p">(</span><span class="n">scene</span><span class="p">,</span><span class="w"> </span><span class="n">geom</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcReleaseGeometry</span><span class="p">(</span><span class="n">geom</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcCommitScene</span><span class="p">(</span><span class="n">scene</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">RTCRayHit</span><span class="w"> </span><span class="n">rayhit</span><span class="p">;</span><span class="w"> </span>
<span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">org_x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">org_y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">org_z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">-1.f</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">dir_x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">dir_y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">dir_z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.f</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">tnear</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">tfar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">numeric_limits</span><span class="o"><</span><span class="kt">float</span><span class="o">>::</span><span class="n">infinity</span><span class="p">();</span><span class="w"></span>
<span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">hit</span><span class="p">.</span><span class="n">geomID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RTC_INVALID_GEOMETRY_ID</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span>
<span class="w"> </span><span class="n">RTCIntersectContext</span><span class="w"> </span><span class="n">context</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcInitIntersectContext</span><span class="p">(</span><span class="o">&</span><span class="n">context</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcIntersect1</span><span class="p">(</span><span class="n">scene</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">context</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">rayhit</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">rayhit</span><span class="p">.</span><span class="n">hit</span><span class="p">.</span><span class="n">geomID</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">RTC_INVALID_GEOMETRY_ID</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"Intersection at t = "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">tfar</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"No Intersection"</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="p">}</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcReleaseScene</span><span class="p">(</span><span class="n">scene</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">rtcReleaseDevice</span><span class="p">(</span><span class="n">device</span><span class="p">);</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">hello_embree.cpp</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2>Step by step</h2>
<p>
We first create several Embree objects: A
Embree device with a default configuration (see sec. 5.1 and 7.1 in the
documention for details), a Embree scene, and a Embree geometry to
represent our triangle.
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">RTCDevice</span><span class="w"> </span><span class="n">device</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rtcNewDevice</span><span class="p">(</span><span class="nb">NULL</span><span class="p">);</span><span class="w"></span>
<span class="n">RTCScene</span><span class="w"> </span><span class="n">scene</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rtcNewScene</span><span class="p">(</span><span class="n">device</span><span class="p">);</span><span class="w"></span>
<span class="n">RTCGeometry</span><span class="w"> </span><span class="n">geometry</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">rtcNewGeometry</span><span class="p">(</span><span class="n">device</span><span class="p">,</span><span class="w"> </span><span class="n">RTC_GEOMETRY_TYPE_TRIANGLE</span><span class="p">);</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Embree device, scene, and geometry.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
A scene is a collection of geometry objects. Scenes are what
the intersect / occluded API functions work on. You can think of a scene as
an acceleration structure, e.g. a bounding-volume hierarchy.
</p>
<p>
Next,
we instruct Embree to create vertex and index buffers into which we copy
the geomety data. For complex scenes, shared buffers are often better
choice but special care must be taken to ensure proper alignment and
padding. This is described in more detail in the API documentation.
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span>
<span class="normal">6</span>
<span class="normal">7</span>
<span class="normal">8</span>
<span class="normal">9</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="kt">float</span><span class="o">*</span><span class="w"> </span><span class="n">vb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="o">*</span><span class="p">)</span><span class="w"> </span><span class="n">rtcSetNewGeometryBuffer</span><span class="p">(</span><span class="n">geom</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">RTC_BUFFER_TYPE_VERTEX</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">RTC_FORMAT_FLOAT3</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="o">*</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">float</span><span class="p">),</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span><span class="w"></span>
<span class="n">vb</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="c1">// 1st vertex</span>
<span class="n">vb</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="c1">// 2nd vertex</span>
<span class="n">vb</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">7</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.f</span><span class="p">;</span><span class="w"> </span><span class="n">vb</span><span class="p">[</span><span class="mi">8</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="c1">// 3rd vertex</span>
<span class="kt">unsigned</span><span class="o">*</span><span class="w"> </span><span class="n">ib</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">unsigned</span><span class="o">*</span><span class="p">)</span><span class="w"> </span><span class="n">rtcSetNewGeometryBuffer</span><span class="p">(</span><span class="n">geom</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">RTC_BUFFER_TYPE_INDEX</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">RTC_FORMAT_UINT3</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="o">*</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">unsigned</span><span class="p">),</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span><span class="w"></span>
<span class="n">ib</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">ib</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">ib</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Vertex and index buffers.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
After setting the geometry data the
geometry can be committed and attached to the scene. Embree objects such as
<code>RTCDevice</code>, <code>RTCScene</code> and <code>RTCGeometry</code>
are reference-counted. This means, that the scene takes ownership of the
geometry when we attach it and we can release the geometry handle. The API
function <code>rtcAttachGeometry</code> returns a geometry ID which can be
used identify intersected objects when the scene contains multiple geometry
objects. We finish the setup by committing the scene, after which the scene
can be intersected.
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">rtcCommitGeometry</span><span class="p">(</span><span class="n">geometry</span><span class="p">);</span><span class="w"></span>
<span class="n">rtcAttachGeometry</span><span class="p">(</span><span class="n">scene</span><span class="p">,</span><span class="w"> </span><span class="n">geometry</span><span class="p">);</span><span class="w"></span>
<span class="n">rtcReleaseGeometry</span><span class="p">(</span><span class="n">geometry</span><span class="p">);</span><span class="w"></span>
<span class="n">rtcCommitScene</span><span class="p">(</span><span class="n">scene</span><span class="p">);</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Attach and commit</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
To perform a ray intersect, we obviously have to create a ray
first. Embree also expects an intersection context which can be used
for advanced features such as intersection filters and instancing.
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span>
<span class="normal">6</span>
<span class="normal">7</span>
<span class="normal">8</span>
<span class="normal">9</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">RTCRayHit</span><span class="w"> </span><span class="n">rayhit</span><span class="p">;</span><span class="w"> </span>
<span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">org_x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">org_y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">org_z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">-1.f</span><span class="p">;</span><span class="w"></span>
<span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">dir_x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">dir_y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">dir_z</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.f</span><span class="p">;</span><span class="w"></span>
<span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">tnear</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.f</span><span class="p">;</span><span class="w"></span>
<span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">tfar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">numeric_limits</span><span class="o"><</span><span class="kt">float</span><span class="o">>::</span><span class="n">infinity</span><span class="p">();</span><span class="w"></span>
<span class="n">rayhit</span><span class="p">.</span><span class="n">hit</span><span class="p">.</span><span class="n">geomID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">RTC_INVALID_GEOMETRY_ID</span><span class="p">;</span><span class="w"></span>
<span class="n">RTCIntersectContext</span><span class="w"> </span><span class="n">context</span><span class="p">;</span><span class="w"></span>
<span class="n">rtcInitIntersectContext</span><span class="p">(</span><span class="o">&</span><span class="n">context</span><span class="p">);</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Intersecting the triangle.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
We set the ray values <code>tnear</code> to
0 and <code>tfar</code> to infinity to indicate that the ray starts at
origin <code>(org_x, org_y, org_z)</code> and is unbounded. We also set
<code>geomID</code> to <code>RTC_INVALID_GEOMETRY_ID</code>. If an
intersection occured, <code>geomID</code> will contain the ID of the
geometry that has been intersected. In this case, the value
<code>tfar</code> will contain the ray parameter which we can compute the
point at which the ray and triangle intersect as
<code>(org_x, org_y, org_z) + t * (dir_x, dir_y, dir_z)</code>.
</p>
<p>
Now
we can call Embree's intersect function and check if the ray intersects the
triangle.
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span>
<span class="normal">6</span>
<span class="normal">7</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">rtcIntersect1</span><span class="p">(</span><span class="n">scene</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">context</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">rayhit</span><span class="p">);</span><span class="w"></span>
<span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">rayhit</span><span class="p">.</span><span class="n">hit</span><span class="p">.</span><span class="n">geomID</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">RTC_INVALID_GEOMETRY_ID</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"Intersection at t = "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">rayhit</span><span class="p">.</span><span class="n">ray</span><span class="p">.</span><span class="n">tfar</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span><span class="w"></span>
<span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"No Intersection"</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Performing a ray intersection with the scene.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
At the end of an application all resources
that where allocated through Embree should be released. Note that the
geometry will be released automatically, when the (last) scene the geometry
is attached to is released.
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">rtcReleaseScene</span><span class="p">(</span><span class="n">scene</span><span class="p">);</span><span class="w"></span>
<span class="n">rtcReleaseDevice</span><span class="p">(</span><span class="n">device</span><span class="p">);</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Be neat and clean up.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2>Building the example</h2>
<p>
To build and run the
example application you can download the latest <a href=https://www.github.com/embree/embree/releases/latest>Embree
release</a>, the <a href=../api_examples/hello_embree/hello_embree.cpp><code>hello_embree.cpp</code></a> source code, and a simple
<a href=../api_examples/hello_embree/CMakeLists.txt><code>CMakeLists.txt</code></a> file.
</p>
<p>
After extracting the Embree release archive and placing <code>hello_embree.cpp</code> and
<code>CMakeLists.txt</code> into the same folder, you can run
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">cmake</span><span class="w"> </span><span class="o">-</span><span class="n">B</span><span class="w"> </span><span class="n">build</span><span class="w"> </span><span class="o">-</span><span class="n">Dembree_DIR</span><span class="o">=/</span><span class="n">path</span><span class="o">/</span><span class="n">to</span><span class="o">/</span><span class="n">extracted</span><span class="o">/</span><span class="n">embree</span><span class="o">/</span><span class="n">release</span><span class="o">/</span><span class="n">lib</span><span class="o">/</span><span class="n">cmake</span><span class="o">/</span><span class="n">embree</span><span class="o">-</span><span class="n">VERSION</span><span class="w"></span>
<span class="n">cmake</span><span class="w"> </span><span class="o">--</span><span class="n">build</span><span class="w"> </span><span class="n">build</span><span class="w"></span>
<span class="p">.</span><span class="o">/</span><span class="n">build</span><span class="o">/</span><span class="n">hello_embree</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Build and run example on Unix-based systems.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
on Unix-based systems or
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">cmake</span><span class="w"> </span><span class="o">-</span><span class="n">B</span><span class="w"> </span><span class="n">build</span><span class="w"> </span><span class="o">-</span><span class="n">Dembree_DIR</span><span class="o">=</span><span class="n">C</span><span class="o">:</span><span class="err">\</span><span class="n">path</span><span class="err">\</span><span class="n">to</span><span class="err">\</span><span class="n">extracted</span><span class="err">\</span><span class="n">embree</span><span class="err">\</span><span class="n">release</span><span class="err">\</span><span class="n">lib</span><span class="err">\</span><span class="n">cmake</span><span class="err">\</span><span class="n">embree</span><span class="o">-</span><span class="n">VERSION</span><span class="w"></span>
<span class="n">cmake</span><span class="w"> </span><span class="o">--</span><span class="n">build</span><span class="w"> </span><span class="n">build</span><span class="w"></span>
<span class="n">build</span><span class="err">\</span><span class="n">Debug</span><span class="err">\</span><span class="n">hello_embree</span><span class="p">.</span><span class="n">exe</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Build and run example on Windows.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2></h2>
<p>
in a developer command prompt for Visual
Studio on windows.
</p>
<p>
The CMake variable <code>embree_DIR</code> has to be
set to the directory which contains the <code>embree-config.cmake</code> file
in the extracted release archive.
</p>
<p>
If everything went smoothly you should get the following output
</p>
</section>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<figure class="figure">
<table class="arvacodetable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span></pre></div></td><td class="code"><div class="arvacode"><pre><span></span><span class="n">Intersection</span><span class="w"> </span><span class="n">at</span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"></span>
</pre></div>
</td></tr></table>
<figcaption class="figure-caption">Output of the example application.</figcaption>
</figure>
</div>
</div>
</div>
<div class="container-lg text"
>
<div class="row justify-content-center py-2">
<div class="col-8">
<section>
<h2>Next steps</h2>
<p>
Some suggestions on how to continue from here:
<ul>
<li>Modify the ray such that it does not intersect the triangle.</li>
<li>Add another triangle to the scene.</li>
<li>Add a <code>RTC_GEOMETRY_TYPE_QUAD</code> geometry to the scene and check
if a ray intersects the correct geometry by inspecting the geomerty IDs.</li>
<li>Take a look at the <a href=https://raw.githubusercontent.com/embree/embree/master/readme.pdf>API documentation</a>.</li>
<li>Take a look at the <a href=https://github.com/embree/embree/tree/master/tutorials>Embree tutorials</a>.</li>
</ul>
</p>
</section>
</div>
</div>
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