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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>glGetLight</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glGetLight"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glGetLight — return light source parameter values</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">glGetLightfv</b>(</code></td><td>GLenum </td><td><var class="pdparam">light</var>, </td></tr><tr><td> </td><td>GLenum </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat * </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glGetLightiv</b>(</code></td><td>GLenum </td><td><var class="pdparam">light</var>, </td></tr><tr><td> </td><td>GLenum </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint * </td><td><var class="pdparam">params</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>light</code></em></span></dt><dd><p>
- Specifies a light source.
- The number of possible lights depends on the implementation,
- but at least eight lights are supported.
- They are identified by symbolic names of the form <code class="constant">GL_LIGHT</code>
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>
- where
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>
- ranges from 0 to the value of <code class="constant">GL_MAX_LIGHTS</code> - 1.
- </p></dd><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p>
- Specifies a light source parameter for <em class="parameter"><code>light</code></em>.
- Accepted symbolic names are
- <code class="constant">GL_AMBIENT</code>,
- <code class="constant">GL_DIFFUSE</code>,
- <code class="constant">GL_SPECULAR</code>,
- <code class="constant">GL_POSITION</code>,
- <code class="constant">GL_SPOT_DIRECTION</code>,
- <code class="constant">GL_SPOT_EXPONENT</code>,
- <code class="constant">GL_SPOT_CUTOFF</code>,
- <code class="constant">GL_CONSTANT_ATTENUATION</code>,
- <code class="constant">GL_LINEAR_ATTENUATION</code>, and
- <code class="constant">GL_QUADRATIC_ATTENUATION</code>.
- </p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p>
- Returns the requested data.
- </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
- <code class="function">glGetLight</code> returns in <em class="parameter"><code>params</code></em> the value or values of a light source parameter.
- <em class="parameter"><code>light</code></em> names the light and is a symbolic name of the form <code class="constant">GL_LIGHT</code>
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>
- where i ranges from 0 to the value of <code class="constant">GL_MAX_LIGHTS</code> - 1.
- <code class="constant">GL_MAX_LIGHTS</code> is an implementation dependent constant that is
- greater than or equal to eight.
- <em class="parameter"><code>pname</code></em> specifies one of ten light source parameters,
- again by symbolic name.
- </p><p>
- The following parameters are defined:
- </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_AMBIENT</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns four integer or floating-point values representing the
- ambient intensity of the light source.
- Integer values,
- when requested,
- are linearly mapped from the internal floating-point representation
- such that 1.0 maps to the most positive representable integer value,
- and
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mn>-1.0</mml:mn>
- </mml:math>
- maps to the most negative representable integer value.
- If the internal value is outside the range
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mfenced open="[" close="]">
- <mml:mn>-1</mml:mn>
- <mml:mn>1</mml:mn>
- </mml:mfenced>
- </mml:math>,
- the corresponding integer return value is undefined. The initial value is
- (0, 0, 0, 1).
- </p></dd><dt><span class="term"><code class="constant">GL_DIFFUSE</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns four integer or floating-point values representing the
- diffuse intensity of the light source.
- Integer values,
- when requested,
- are linearly mapped from the internal floating-point representation
- such that 1.0 maps to the most positive representable integer value,
- and
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mn>-1.0</mml:mn>
- </mml:math>
- maps to the most negative representable integer value.
- If the internal value is outside the range
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mfenced open="[" close="]">
- <mml:mn>-1</mml:mn>
- <mml:mn>1</mml:mn>
- </mml:mfenced>
- </mml:math>,
- the corresponding integer return value is undefined. The initial value
- for <code class="constant">GL_LIGHT0</code> is (1, 1, 1, 1); for other lights, the
- initial value is (0, 0, 0, 0).
- </p></dd><dt><span class="term"><code class="constant">GL_SPECULAR</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns four integer or floating-point values representing the
- specular intensity of the light source.
- Integer values,
- when requested,
- are linearly mapped from the internal floating-point representation
- such that 1.0 maps to the most positive representable integer value,
- and
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mn>-1.0</mml:mn>
- </mml:math>
- maps to the most negative representable integer value.
- If the internal value is outside the range
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mfenced open="[" close="]">
- <mml:mn>-1</mml:mn>
- <mml:mn>1</mml:mn>
- </mml:mfenced>
- </mml:math>,
- the corresponding integer return value is undefined. The initial value
- for <code class="constant">GL_LIGHT0</code> is (1, 1, 1, 1); for other lights, the
- initial value is (0, 0, 0, 0).
- </p></dd><dt><span class="term"><code class="constant">GL_POSITION</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns four integer or floating-point values representing the
- position of the light source.
- Integer values,
- when requested,
- are computed by rounding the internal floating-point values to the
- nearest integer value.
- The returned values are those maintained in eye coordinates.
- They will not be equal to the values specified using <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>,
- unless the modelview matrix was identity at the time <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a> was
- called. The initial value is (0, 0, 1, 0).
- </p></dd><dt><span class="term"><code class="constant">GL_SPOT_DIRECTION</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns three integer or floating-point values representing the
- direction of the light source.
- Integer values,
- when requested,
- are computed by rounding the internal floating-point values to the
- nearest integer value.
- The returned values are those maintained in eye coordinates.
- They will not be equal to the values specified using <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>,
- unless the modelview matrix was identity at the time <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a> was called.
- Although spot direction is normalized before being used in the lighting
- equation,
- the returned values are the transformed versions of the specified values
- prior to normalization. The initial value is
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
-
- <mml:mfenced open="(" close=")">
- <mml:mn>0</mml:mn>
- <mml:mn>0</mml:mn>
- <mml:mn>-1</mml:mn>
- </mml:mfenced>
- </mml:math>.
- </p></dd><dt><span class="term"><code class="constant">GL_SPOT_EXPONENT</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns a single integer or floating-point value representing the
- spot exponent of the light.
- An integer value,
- when requested,
- is computed by rounding the internal floating-point representation to
- the nearest integer. The initial value is 0.
- </p></dd><dt><span class="term"><code class="constant">GL_SPOT_CUTOFF</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns a single integer or floating-point value representing the
- spot cutoff angle of the light.
- An integer value,
- when requested,
- is computed by rounding the internal floating-point representation to
- the nearest integer. The initial value is 180.
- </p></dd><dt><span class="term"><code class="constant">GL_CONSTANT_ATTENUATION</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns a single integer or floating-point value representing the
- constant (not distance-related) attenuation of the light.
- An integer value,
- when requested,
- is computed by rounding the internal floating-point representation to
- the nearest integer. The initial value is 1.
- </p></dd><dt><span class="term"><code class="constant">GL_LINEAR_ATTENUATION</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns a single integer or floating-point value representing the
- linear attenuation of the light.
- An integer value,
- when requested,
- is computed by rounding the internal floating-point representation to
- the nearest integer. The initial value is 0.
- </p></dd><dt><span class="term"><code class="constant">GL_QUADRATIC_ATTENUATION</code></span></dt><dd><p>
- <em class="parameter"><code>params</code></em> returns a single integer or floating-point value representing the
- quadratic attenuation of the light.
- An integer value,
- when requested,
- is computed by rounding the internal floating-point representation to
- the nearest integer. The initial value is 0.
- </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
- It is always the case that <code class="constant">GL_LIGHT</code>
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>
- = <code class="constant">GL_LIGHT0</code> +
- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>.
- </p><p>
- If an error is generated,
- no change is made to the contents of <em class="parameter"><code>params</code></em>.
- </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
- <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>light</code></em> or <em class="parameter"><code>pname</code></em> is not an
- accepted value.
- </p><p>
- <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glGetLight</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="seealso"></a><h2>See Also</h2><p>
- <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</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>
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