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      <title>glPolygonOffset - OpenGL ES 3.1 Reference Pages</title>
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      <div class="refentry" id="glPolygonOffset">
        <div class="titlepage"/>
        <div class="refnamediv">
          <h2>Name</h2>
          <p>glPolygonOffset — set the scale and units used to calculate depth values</p>
        </div>
        <div class="refsynopsisdiv">
          <h2>C Specification</h2>
          <div class="funcsynopsis">
            <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
              <tr>
                <td>
                  <code class="funcdef">void <strong class="fsfunc">glPolygonOffset</strong>(</code>
                </td>
                <td>GLfloat <var class="pdparam">factor</var>, </td>
              </tr>
              <tr>
                <td> </td>
                <td>GLfloat <var class="pdparam">units</var><code>)</code>;</td>
              </tr>
            </table>
            <div class="funcprototype-spacer"> </div>
          </div>
        </div>
        <div class="refsect1" id="parameters">
          <h2>Parameters</h2>
          <div class="variablelist">
            <dl class="variablelist">
              <dt>
                <span class="term">
                  <em class="parameter">
                    <code>factor</code>
                  </em>
                </span>
              </dt>
              <dd>
                <p>
                      Specifies a scale factor that is used to create a variable
                      depth offset for each polygon. The initial value is 0.
                  </p>
              </dd>
              <dt>
                <span class="term">
                  <em class="parameter">
                    <code>units</code>
                  </em>
                </span>
              </dt>
              <dd>
                <p>
                      Is multiplied by an implementation-specific value to
                      create a constant depth offset. The initial value is 0.
                  </p>
              </dd>
            </dl>
          </div>
        </div>
        <div class="refsect1" id="description">
          <h2>Description</h2>
          <p>
              When <code class="constant">GL_POLYGON_OFFSET_FILL</code> is enabled, each
              fragment's <span class="emphasis"><em>depth</em></span> value will be offset after it is interpolated
              from the <span class="emphasis"><em>depth</em></span> values of the appropriate vertices.
              The value of the offset is
              <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                  
                  <mml:mrow>
                      <mml:mrow>
                          <mml:mi mathvariant="italic">factor</mml:mi>
                          <mml:mo>×</mml:mo>
                          <mml:mi mathvariant="italic">DZ</mml:mi>
                      </mml:mrow>
                      <mml:mo>+</mml:mo>
                      <mml:mrow>
                          <mml:mi mathvariant="italic">r</mml:mi>
                          <mml:mo>×</mml:mo>
                          <mml:mi mathvariant="italic">units</mml:mi>
                      </mml:mrow>
                  </mml:mrow>
              </mml:math>,
              where
              <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                  
                  <mml:mi mathvariant="italic">DZ</mml:mi>
              </mml:math>
              is a measurement of the change in depth relative to the screen
              area of the polygon, and
              <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">r</mml:mi></mml:math>
              is the smallest value that is guaranteed to
              produce a resolvable offset for a given implementation.
              The offset is added before the depth test is performed and before
              the value is written into the depth buffer.
          </p>
          <p>
              <code class="function">glPolygonOffset</code> is useful for applying decals.
          </p>
        </div>
        <div class="refsect1" id="associatedgets">
          <h2>Associated Gets</h2>
          <p>
              <a class="citerefentry" href="glIsEnabled.xhtml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument
              <code class="constant">GL_POLYGON_OFFSET_FILL</code>.
          </p>
          <p>
              <a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_POLYGON_OFFSET_FACTOR</code> or
              <code class="constant">GL_POLYGON_OFFSET_UNITS</code>.
          </p>
        </div>
        <div class="refsect1" id="versions">
          <h2>API Version Support</h2>
          <div class="informaltable">
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                <col style="text-align: center; " class="lastvers"/>
              </colgroup>
              <thead>
                <tr>
                  <th style="text-align: left; border-right: 2px solid ; ">
                   
              </th>
                  <th style="text-align: center; border-bottom: 2px solid ; " colspan="3">
                  <span class="bold"><strong>OpenGL ES API Version</strong></span>
              </th>
                </tr>
                <tr>
                  <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                  <span class="bold"><strong>Function Name</strong></span>
              </th>
                  <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                  <span class="bold"><strong>2.0</strong></span>
              </th>
                  <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                  <span class="bold"><strong>3.0</strong></span>
              </th>
                  <th style="text-align: center; border-bottom: 2px solid ; ">
                  <span class="bold"><strong>3.1</strong></span>
              </th>
                </tr>
              </thead>
              <tbody>
                <tr>
                  <td style="text-align: left; border-right: 2px solid ; ">glPolygonOffset</td>
                  <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                  <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                  <td style="text-align: center; ">✔</td>
                </tr>
              </tbody>
            </table>
          </div>
        </div>
        <div class="refsect1" id="seealso">
          <h2>See Also</h2>
          <p>
              <a class="citerefentry" href="glDepthFunc.xhtml"><span class="citerefentry"><span class="refentrytitle">glDepthFunc</span></span></a>,
              <a class="citerefentry" href="glEnable.xhtml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>,
              <a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>,
              <a class="citerefentry" href="glIsEnabled.xhtml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a>
          </p>
        </div>
        <div class="refsect1" id="Copyright">
          <h2>Copyright</h2>
          <p>
              Copyright <span class="trademark"/>© 1991-2006 Silicon Graphics, Inc.
              Copyright <span class="trademark"/>© 2010-2014 Khronos Group.
              This document is licensed under the SGI Free Software B License.
              For details, see
              <a class="link" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
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