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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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                <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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