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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 V1.78.1" /></head><body><div class="refentry"><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" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glOrthof</strong>(</code></td><td>GLfloat <var class="pdparam">left</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">right</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">bottom</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">top</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">near</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">far</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glOrthox</strong>(</code></td><td>GLfixed <var class="pdparam">left</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">right</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">bottom</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">top</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">near</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">far</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term">
		<em class="parameter"><code>left</code></em>,
		<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>,
		<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>near</code></em>,
		<em class="parameter"><code>far</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"><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><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
	    <mml:mrow>
		<mml:mo>(</mml:mo>
		<mml:mtable class="matrix">
		    <mml:mtr>
			<mml:mtd>
			    <mml:mfrac>
				<mml:mn>2</mml:mn>
				<mml:mrow><mml:mi>right</mml:mi><mml:mo>-</mml:mo><mml:mi>left</mml:mi></mml:mrow>
			    </mml:mfrac>
			</mml:mtd>
			<mml:mtd><mml:mn>0</mml:mn></mml:mtd>
			<mml:mtd><mml:mn>0</mml:mn></mml:mtd>
			<mml:mtd><mml:msub><mml:mi>t</mml:mi><mml:mi>x</mml:mi></mml:msub></mml:mtd>
		    </mml:mtr>
		    <mml:mtr>
			<mml:mtd><mml:mn>0</mml:mn></mml:mtd>
			<mml:mtd>
			    <mml:mfrac>
				<mml:mn>2</mml:mn>
				<mml:mrow><mml:mi>top</mml:mi><mml:mo>-</mml:mo><mml:mi>bottom</mml:mi></mml:mrow>
			    </mml:mfrac>
			</mml:mtd>
			<mml:mtd><mml:mn>0</mml:mn></mml:mtd>
			<mml:mtd><mml:msub><mml:mi>t</mml:mi><mml:mi>y</mml:mi></mml:msub></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:mfrac>
				<mml:mrow><mml:mo>-</mml:mo><mml:mn>2</mml:mn></mml:mrow>
				<mml:mrow><mml:mi>far</mml:mi><mml:mo>-</mml:mo><mml:mi>near</mml:mi></mml:mrow>
			    </mml:mfrac>
			</mml:mtd>
			<mml:mtd><mml:msub><mml:mi>t</mml:mi><mml:mi>z</mml:mi></mml:msub></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:mo>)</mml:mo>
	    </mml:mrow>
	</mml:math></div><p>where</p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mtable>
	    <mml:mtr><mml:mtd>
		<mml:msub><mml:mi>t</mml:mi><mml:mi>x</mml:mi></mml:msub>
		<mml:mgroupalign></mml:mgroupalign>
		<mml:mo>=</mml:mo>
		<mml:mgroupalign></mml:mgroupalign>
		<mml:mo>-</mml:mo>
		<mml:mfrac>
		    <mml:mrow><mml:mi>right</mml:mi><mml:mo>+</mml:mo><mml:mi>left</mml:mi></mml:mrow>
		    <mml:mrow><mml:mi>right</mml:mi><mml:mo>-</mml:mo><mml:mi>left</mml:mi></mml:mrow>
		</mml:mfrac>
	    </mml:mtd></mml:mtr>
	    <mml:mtr><mml:mtd>
		<mml:msub><mml:mi>t</mml:mi><mml:mi>y</mml:mi></mml:msub>
		<mml:mgroupalign></mml:mgroupalign>
		<mml:mo>=</mml:mo>
		<mml:mgroupalign></mml:mgroupalign>
		<mml:mo>-</mml:mo>
		<mml:mfrac>
		    <mml:mrow><mml:mi>top</mml:mi><mml:mo>+</mml:mo><mml:mi>bottom</mml:mi></mml:mrow>
		    <mml:mrow><mml:mi>top</mml:mi><mml:mo>-</mml:mo><mml:mi>bottom</mml:mi></mml:mrow>
		</mml:mfrac>
	    </mml:mtd></mml:mtr>
	    <mml:mtr><mml:mtd>
		<mml:msub><mml:mi>t</mml:mi><mml:mi>z</mml:mi></mml:msub>
		<mml:mgroupalign></mml:mgroupalign>
		<mml:mo>=</mml:mo>
		<mml:mgroupalign></mml:mgroupalign>
		<mml:mo>-</mml:mo>
		<mml:mfrac>
		    <mml:mrow><mml:mi>far</mml:mi><mml:mo>+</mml:mo><mml:mi>near</mml:mi></mml:mrow>
		    <mml:mrow><mml:mi>far</mml:mi><mml:mo>-</mml:mo><mml:mi>near</mml:mi></mml:mrow>
		</mml:mfrac>
	    </mml:mtd></mml:mtr>
	</mml:mtable></mml:math></div><p>Typically, the matrix mode is
	<code class="constant">GL_PROJECTION</code>, and
	(<em class="parameter"><code>left</code></em>, <em class="parameter"><code>bottom</code></em>,
	-<em class="parameter"><code>near</code></em>) and
	(<em class="parameter"><code>right</code></em>, <em class="parameter"><code>top</code></em>,
	-<em class="parameter"><code>near</code></em>)
	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).
	-<em class="parameter"><code>far</code></em>
	specifies the location of the far clipping plane. Both
	<em class="parameter"><code>near</code></em> and <em class="parameter"><code>far</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"><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></div><div class="refsect1"><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"><a id="copyright"></a><h2>Copyright</h2><p>
	    Copyright <span class="trademark"></span>© 2003-2004
	    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>