<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" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glGetLightfv</b>(</code></td><td>GLenum <var class="pdparam">light</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat * <var class="pdparam">params</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glGetLightxv</b>(</code></td><td>GLenum <var class="pdparam">light</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfixed * <var class="pdparam">params</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></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

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">

<mml:mi>GL_LIGHTi</mml:mi> where

<mml:mi>0</mml:mi><mml:mo>&lt;</mml:mo><mml:mi>i</mml:mi><mml:mo>&lt;</mml:mo>

<mml:mi>GL_MAX_LIGHTS</mml:mi>

</mml:math>

</p></dd><dt><span class="term">

<em class="parameter"><code>pname</code></em>

</span></dt><dd><p>

Specifies a light source parameter for light.

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

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">

<mml:mi>GL_LIGHTi</mml:mi> for

<mml:mi>0</mml:mi><mml:mo>&lt;</mml:mo><mml:mi>i</mml:mi><mml:mo>&lt;</mml:mo>

<mml:mi>GL_MAX_LIGHTS</mml:mi>

</mml:math>

where <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 ten light 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 fixed-point or floating-point values that

specify the ambient RGBA intensity of the light. Both

fixed-point and floating-point values are mapped

directly. Neither fixed-point nor floating-point values

are clamped.

The initial ambient light intensity 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 fixed-point or floating-point values that

specify the diffuse RGBA intensity of the light. Both

fixed-point and floating-point values are mapped

directly. Neither fixed-point nor floating-point values

are clamped.

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 fixed-point or floating-point values that

specify the specular RGBA intensity of the light. Both

fixed-point and floating-point values are mapped

directly. Neither fixed-point nor floating-point values

are clamped.

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 fixed-point or floating-point values representing the

position of the light source.

Both fixed-point and floating-point values are mapped

directly.

The returned values are those maintained in eye coordinates.

They will not be equal to the values specified using <a class="citerefentry" href="glLight"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>,

unless the modelview matrix was identity at the time <a class="citerefentry" href="glLight"><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 fixed-point or floating-point values that

specify the direction of the light in homogeneous object

coordinates. Both fixed-point and floating-point values

are mapped directly. Neither fixed-point nor

floating-point values are clamped.

The initial direction is (0, 0, -1).

</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 fixed-point or floating-point value that

specifies the intensity distribution of the light.

Fixed-point and floating-point values are mapped

directly. Only values in the range [0, 128] are

accepted.

The initial spot exponent 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 fixed-point or floating-point value that

specifies the maximum spread angle of a light source.

Fixed-point and floating-point values are mapped

directly. Only values in the range [0, 90] and the special

value 180 are accepted. If the angle between the

direction of the light and the direction from the light

to the vertex being lighted is greater than the spot

cutoff angle, the light is completely masked.

Otherwise, its intensity is controlled by the spot

exponent and the attenuation factors. The initial spot

cutoff is 180.

</p></dd><dt><span class="term">

<code class="constant">GL_CONSTANT_ATTENUATION</code>,

<code class="constant">GL_LINEAR_ATTENUATION</code>,

<code class="constant">GL_QUADRATIC_ATTENUATION</code>

</span></dt><dd><p><em class="parameter"><code>params</code></em>

returns a single fixed-point or floating-point value that

specifies one of the three light attenuation factors.

Fixed-point and floating-point values are mapped

directly. Only nonnegative values are accepted. If the

light is positional, rather than directional, its

intensity is attenuated by the reciprocal of the sum of

the constant factor, the linear factor times the distance

between the light and the vertex being lighted, and the

quadratic factor times the square of the same distance.

The initial attenuation factors are (1, 0, 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

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">

<mml:mi>GL_LIGHTi</mml:mi><mml:mo>=</mml:mo>

<mml:mi>GL_LIGHT0</mml:mi><mml:mo>+</mml:mo><code class="constant">i</code>.

</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></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>

<a class="citerefentry" href="glLight"><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>© 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>