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<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glOrtho</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glOrtho"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glOrtho — multiply the current matrix with an orthographic matrix</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glOrtho</b>(</code></td><td>GLdouble  </td><td><var class="pdparam">left</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">right</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">bottom</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">top</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">nearVal</var>, </td></tr><tr><td> </td><td>GLdouble  </td><td><var class="pdparam">farVal</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>left</code></em>, </span><span class="term"><em class="parameter"><code>right</code></em></span></dt><dd><p>
                    Specify the coordinates for the left and right vertical clipping planes.
                </p></dd><dt><span class="term"><em class="parameter"><code>bottom</code></em>, </span><span class="term"><em class="parameter"><code>top</code></em></span></dt><dd><p>
                    Specify the coordinates for the bottom and top horizontal clipping planes.
                </p></dd><dt><span class="term"><em class="parameter"><code>nearVal</code></em>, </span><span class="term"><em class="parameter"><code>farVal</code></em></span></dt><dd><p>
                    Specify the distances to the nearer and farther depth clipping planes.
                    These values are negative if the plane is to be behind the viewer.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glOrtho</code> describes a transformation that produces a parallel projection.
            The current matrix (see <a class="citerefentry" href="glMatrixMode.xml"><span class="citerefentry"><span class="refentrytitle">glMatrixMode</span></span></a>) is multiplied by this matrix
            and the result replaces the current matrix, as if
            <a class="citerefentry" href="glMultMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glMultMatrix</span></span></a> were called with the following matrix
            as its argument:
        </p><p>
            </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mfenced open="(" close=")">
                    <mml:mtable>
                        <mml:mtr>
                            <mml:mtd>
                                <mml:mfenced open="" close="">
                                    <mml:mfrac>
                                        <mml:mn>2</mml:mn>
                                        <mml:mfenced open="" close="">
                                            <mml:mrow>
                                                <mml:mi mathvariant="italic">right</mml:mi>
                                                <mml:mo>-</mml:mo>
                                                <mml:mi mathvariant="italic">left</mml:mi>
                                            </mml:mrow>
                                        </mml:mfenced>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mfenced open="" close="">
                                    <mml:msub><mml:mi mathvariant="italic">t</mml:mi>
                                    <mml:mi mathvariant="italic">x</mml:mi>
                                    </mml:msub>
                                </mml:mfenced>
                            </mml:mtd>
                        </mml:mtr>
                        <mml:mtr>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mfenced open="" close="">
                                    <mml:mfrac>
                                        <mml:mn>2</mml:mn>
                                        <mml:mfenced open="" close="">
                                            <mml:mrow>
                                                <mml:mi mathvariant="italic">top</mml:mi>
                                                <mml:mo>-</mml:mo>
                                                <mml:mi mathvariant="italic">bottom</mml:mi>
                                            </mml:mrow>
                                        </mml:mfenced>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mfenced open="" close="">
                                    <mml:msub><mml:mi mathvariant="italic">t</mml:mi>
                                    <mml:mi mathvariant="italic">y</mml:mi>
                                    </mml:msub>
                                </mml:mfenced>
                            </mml:mtd>
                        </mml:mtr>
                        <mml:mtr>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mfenced open="" close="">
                                    <mml:mfrac>
                                        <mml:mn>-2</mml:mn>
                                        <mml:mfenced open="" close="">
                                            <mml:mrow>
                                                <mml:mi mathvariant="italic">farVal</mml:mi>
                                                <mml:mo>-</mml:mo>
                                                <mml:mi mathvariant="italic">nearVal</mml:mi>
                                            </mml:mrow>
                                        </mml:mfenced>
                                    </mml:mfrac>
                                </mml:mfenced>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mfenced open="" close="">
                                    <mml:msub><mml:mi mathvariant="italic">t</mml:mi>
                                    <mml:mi mathvariant="italic">z</mml:mi>
                                    </mml:msub>
                                </mml:mfenced>
                            </mml:mtd>
                        </mml:mtr>
                        <mml:mtr>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>0</mml:mn>
                            </mml:mtd>
                            <mml:mtd>
                                <mml:mn>1</mml:mn>
                            </mml:mtd>
                        </mml:mtr>
                    </mml:mtable>
                </mml:mfenced>
            </mml:math></div><p>
        </p><p>
            where
            </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">t</mml:mi>
                    <mml:mi mathvariant="italic">x</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mo>-</mml:mo>
                        <mml:mfenced open="" close="">
                            <mml:mfrac>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mi mathvariant="italic">right</mml:mi>
                                        <mml:mo>+</mml:mo>
                                        <mml:mi mathvariant="italic">left</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mi mathvariant="italic">right</mml:mi>
                                        <mml:mo>-</mml:mo>
                                        <mml:mi mathvariant="italic">left</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                            </mml:mfrac>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></div><p>
            </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">t</mml:mi>
                    <mml:mi mathvariant="italic">y</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mo>-</mml:mo>
                        <mml:mfenced open="" close="">
                            <mml:mfrac>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mi mathvariant="italic">top</mml:mi>
                                        <mml:mo>+</mml:mo>
                                        <mml:mi mathvariant="italic">bottom</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mi mathvariant="italic">top</mml:mi>
                                        <mml:mo>-</mml:mo>
                                        <mml:mi mathvariant="italic">bottom</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                            </mml:mfrac>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></div><p>
            </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">t</mml:mi>
                    <mml:mi mathvariant="italic">z</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mo>-</mml:mo>
                        <mml:mfenced open="" close="">
                            <mml:mfrac>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mi mathvariant="italic">farVal</mml:mi>
                                        <mml:mo>+</mml:mo>
                                        <mml:mi mathvariant="italic">nearVal</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mi mathvariant="italic">farVal</mml:mi>
                                        <mml:mo>-</mml:mo>
                                        <mml:mi mathvariant="italic">nearVal</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                            </mml:mfrac>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></div><p>
        </p><p>
            Typically, the matrix mode is <code class="constant">GL_PROJECTION</code>, and
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mfenced open="(" close=")">
                    <mml:mi mathvariant="italic">left</mml:mi>
                    <mml:mi mathvariant="italic">bottom</mml:mi>
                    <mml:mrow>
                        <mml:mo>-</mml:mo>
                        <mml:mi mathvariant="italic">nearVal</mml:mi>
                    </mml:mrow>
                </mml:mfenced>
            </mml:math>
            and 
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mfenced open="(" close=")">
                    <mml:mi mathvariant="italic">right</mml:mi>
                    <mml:mi mathvariant="italic">top</mml:mi>
                    <mml:mrow>
                        <mml:mo>-</mml:mo>
                        <mml:mi mathvariant="italic">nearVal</mml:mi>
                    </mml:mrow>
                </mml:mfenced>
            </mml:math>
            specify the points on the near clipping plane that are mapped
            to the lower left and upper right corners of the window,
            respectively,
            assuming that the eye is located at (0, 0, 0).
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:mo>-</mml:mo>
                    <mml:mi mathvariant="italic">farVal</mml:mi>
                </mml:mrow>
            </mml:math>
            specifies the location of the far clipping plane.
            Both <em class="parameter"><code>nearVal</code></em> and <em class="parameter"><code>farVal</code></em> can be either positive or negative.
        </p><p>
            Use <a class="citerefentry" href="glPushMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glPushMatrix</span></span></a> and <a class="citerefentry" href="glPopMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glPopMatrix</span></span></a> to save and restore
            the current matrix stack.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if
            <em class="parameter"><code>left</code></em> = <em class="parameter"><code>right</code></em>, or
            <em class="parameter"><code>bottom</code></em> = <em class="parameter"><code>top</code></em>, or
            <em class="parameter"><code>near</code></em> = <em class="parameter"><code>far</code></em>.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glOrtho</code>
            is executed between the execution of
            <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
            and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MATRIX_MODE</code>
        </p><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_COLOR_MATRIX</code>
        </p><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MODELVIEW_MATRIX</code>
        </p><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_PROJECTION_MATRIX</code>
        </p><p>
            <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_TEXTURE_MATRIX</code>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glFrustum.xml"><span class="citerefentry"><span class="refentrytitle">glFrustum</span></span></a>,
            <a class="citerefentry" href="glMatrixMode.xml"><span class="citerefentry"><span class="refentrytitle">glMatrixMode</span></span></a>,
            <a class="citerefentry" href="glMultMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glMultMatrix</span></span></a>,
            <a class="citerefentry" href="glPushMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glPushMatrix</span></span></a>,
            <a class="citerefentry" href="glViewport.xml"><span class="citerefentry"><span class="refentrytitle">glViewport</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>
