[clinton/guile-figl.git] / upstream-doc / man2 / glLightModel.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
              "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glLightModel">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glLightModel</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glLightModel</refname>
        <refpurpose>set the lighting model parameters</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glLightModelf</function></funcdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>GLfloat <parameter>param</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glLightModeli</function></funcdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>GLint <parameter>param</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>pname</parameter></term>
            <listitem>
                <para>
                    Specifies a single-valued lighting model parameter.
                    <constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant>,
                    <constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant>, and
                    <constant>GL_LIGHT_MODEL_TWO_SIDE</constant> are accepted.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>param</parameter></term>
            <listitem>
                <para>
                    Specifies the value that <parameter>param</parameter> will be set to.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glLightModelfv</function></funcdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>const GLfloat * <parameter>params</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glLightModeliv</function></funcdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>const GLint * <parameter>params</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters2"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>pname</parameter></term>
            <listitem>
                <para>
                    Specifies a lighting model parameter.
                    <constant>GL_LIGHT_MODEL_AMBIENT</constant>,
                    <constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant>,
                    <constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant>, and
                    <constant>GL_LIGHT_MODEL_TWO_SIDE</constant> are accepted.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>params</parameter></term>
            <listitem>
                <para>
                    Specifies a pointer to the value or values that <parameter>params</parameter> will be set to.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glLightModel</function> sets the lighting model parameter.
            <parameter>pname</parameter> names a parameter and <parameter>params</parameter> gives the new value.
            There are three lighting model parameters:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_LIGHT_MODEL_AMBIENT</constant></term>
                <listitem>
                    <para>
                    </para>
                    <para>
                        <parameter>params</parameter> contains four integer or floating-point values that specify
                        the ambient RGBA intensity of the entire scene.
                        Integer values are mapped linearly such that the most positive representable
                        value maps to 1.0,
                        and the most negative representable value maps to 
                        <inlineequation><mml:math>
                            <!-- eqn: -1.0:-->
                            <mml:mn>-1.0</mml:mn>
                        </mml:math></inlineequation>.
                        Floating-point values are mapped directly.
                        Neither integer nor floating-point values are clamped.
                        The initial ambient scene intensity is (0.2, 0.2, 0.2, 1.0).
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant></term>
                <listitem>
                    <para>
                    </para>
                    <para>
                        <parameter>params</parameter> must be either <constant>GL_SEPARATE_SPECULAR_COLOR</constant> or
                        <constant>GL_SINGLE_COLOR</constant>.
                        <constant>GL_SINGLE_COLOR</constant> specifies that a single color is generated from the
                        lighting computation for a vertex.  <constant>GL_SEPARATE_SPECULAR_COLOR</constant>
                        specifies that the specular color computation of lighting be stored
                        separately from the remainder of the lighting computation.  The specular
                        color is summed into the generated fragment's color after the application
                        of texture mapping (if enabled).  The initial value is <constant>GL_SINGLE_COLOR</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant></term>
                <listitem>
                    <para>
                    </para>
                    <para>
                        <parameter>params</parameter> is a single integer or floating-point value that specifies
                        how specular reflection angles are computed.
                        If <parameter>params</parameter> is 0 (or 0.0), specular reflection angles take the
                        view direction to be parallel to and in the direction of the -<emphasis>z</emphasis> axis,
                        regardless of the location of the vertex in eye coordinates.
                        Otherwise, specular reflections are computed from the origin
                        of the eye coordinate system.
                        The initial value is 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_LIGHT_MODEL_TWO_SIDE</constant></term>
                <listitem>
                    <para>
                    </para>
                    <para>
                        <parameter>params</parameter> is a single integer or floating-point value that specifies
                        whether one- or two-sided lighting calculations are done for polygons.
                        It has no effect on the lighting calculations for points,
                        lines,
                        or bitmaps.
                        If <parameter>params</parameter> is 0 (or 0.0), one-sided lighting is specified,
                        and only the <emphasis>front</emphasis> material parameters are used in the
                        lighting equation.
                        Otherwise, two-sided lighting is specified.
                        In this case, vertices of back-facing polygons are lighted using the
                        <emphasis>back</emphasis> material parameters
                        and have their normals reversed before the lighting equation is evaluated.
                        Vertices of front-facing polygons are always lighted using the
                        <emphasis>front</emphasis> material parameters,
                        with no change to their normals. The initial value is 0.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
        <para>
            In RGBA mode, the lighted color of a vertex is the sum of
            the material emission intensity,
            the product of the material ambient reflectance and the lighting model full-scene
            ambient intensity,
            and the contribution of each enabled light source.
            Each light source contributes the sum of three terms:
            ambient, diffuse, and specular.
            The ambient light source contribution is the product of the material ambient
            reflectance and the light's ambient intensity.
            The diffuse light source contribution is the product of the material diffuse
            reflectance,
            the light's diffuse intensity,
            and the dot product of the vertex's normal with the normalized vector from
            the vertex to the light source.
            The specular light source contribution is the product of the material specular
            reflectance,
            the light's specular intensity,
            and the dot product of the normalized vertex-to-eye and vertex-to-light
            vectors,
            raised to the power of the shininess of the material.
            All three light source contributions are attenuated equally based on
            the distance from the vertex to the light source and on light source
            direction, spread exponent, and spread cutoff angle.
            All dot products are replaced with 0 if they evaluate to a negative value.
        </para>
        <para>
            The alpha component of the resulting lighted color is set to the alpha value
            of the material diffuse reflectance.
        </para>
        <para>
            In color index mode,
            the value of the lighted index of a vertex ranges from the ambient
            to the specular values passed to <citerefentry><refentrytitle>glMaterial</refentrytitle></citerefentry> using <constant>GL_COLOR_INDEXES</constant>.
            Diffuse and specular coefficients,
            computed with a (.30, .59, .11) weighting of the lights' colors,
            the shininess of the material,
            and the same reflection and attenuation equations as in the RGBA case,
            determine how much above ambient the resulting index is.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            <constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant> is available only if the GL version is
            1.2 or greater.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is not an accepted value.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is
            <constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant> and <parameter>params</parameter> is not one of
            <constant>GL_SINGLE_COLOR</constant> or <constant>GL_SEPARATE_SPECULAR_COLOR</constant>.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glLightModel</function> is executed between
            the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_AMBIENT</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_TWO_SIDE</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_LIGHTING</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glLight</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glMaterial</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
        </para>
    </refsect1>
</refentry>
Commit	Line	Data
7faf1d71 AW	1	<?xml version="1.0" encoding="UTF-8"?>
	2	<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
	3	"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
	4	<refentry id="glLightModel">
	5	<refmeta>
	6	<refmetainfo>
	7	<copyright>
	8	<year>1991-2006</year>
	9	<holder>Silicon Graphics, Inc.</holder>
	10	</copyright>
	11	</refmetainfo>
	12	<refentrytitle>glLightModel</refentrytitle>
	13	<manvolnum>3G</manvolnum>
	14	</refmeta>
	15	<refnamediv>
	16	<refname>glLightModel</refname>
	17	<refpurpose>set the lighting model parameters</refpurpose>
	18	</refnamediv>
	19	<refsynopsisdiv><title>C Specification</title>
	20	<funcsynopsis>
	21	<funcprototype>
	22	<funcdef>void <function>glLightModelf</function></funcdef>
	23	<paramdef>GLenum <parameter>pname</parameter></paramdef>
	24	<paramdef>GLfloat <parameter>param</parameter></paramdef>
	25	</funcprototype>
	26	</funcsynopsis>
	27	<funcsynopsis>
	28	<funcprototype>
	29	<funcdef>void <function>glLightModeli</function></funcdef>
	30	<paramdef>GLenum <parameter>pname</parameter></paramdef>
	31	<paramdef>GLint <parameter>param</parameter></paramdef>
	32	</funcprototype>
	33	</funcsynopsis>
	34	</refsynopsisdiv>
	35	<!-- eqn: ignoring delim $$ -->
	36	<refsect1 id="parameters"><title>Parameters</title>
	37	<variablelist>
	38	<varlistentry>
	39	<term><parameter>pname</parameter></term>
	40	<listitem>
	41	<para>
	42	Specifies a single-valued lighting model parameter.
	43	<constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant>,
	44	<constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant>, and
	45	<constant>GL_LIGHT_MODEL_TWO_SIDE</constant> are accepted.
	46	</para>
	47	</listitem>
	48	</varlistentry>
	49	<varlistentry>
	50	<term><parameter>param</parameter></term>
	51	<listitem>
	52	<para>
	53	Specifies the value that <parameter>param</parameter> will be set to.
	54	</para>
	55	</listitem>
	56	</varlistentry>
	57	</variablelist>
	58	</refsect1>
	59	<refsynopsisdiv><title>C Specification</title>
	60	<funcsynopsis>
	61	<funcprototype>
	62	<funcdef>void <function>glLightModelfv</function></funcdef>
	63	<paramdef>GLenum <parameter>pname</parameter></paramdef>
	64	<paramdef>const GLfloat * <parameter>params</parameter></paramdef>
65	</funcprototype>
66	</funcsynopsis>
67	<funcsynopsis>
68	<funcprototype>
69	<funcdef>void <function>glLightModeliv</function></funcdef>
70	<paramdef>GLenum <parameter>pname</parameter></paramdef>
71	<paramdef>const GLint * <parameter>params</parameter></paramdef>
72	</funcprototype>
73	</funcsynopsis>
74	</refsynopsisdiv>
75	<refsect1 id="parameters2"><title>Parameters</title>
76	<variablelist>
77	<varlistentry>
78	<term><parameter>pname</parameter></term>
79	<listitem>
80	<para>
81	Specifies a lighting model parameter.
82	<constant>GL_LIGHT_MODEL_AMBIENT</constant>,
83	<constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant>,
84	<constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant>, and
85	<constant>GL_LIGHT_MODEL_TWO_SIDE</constant> are accepted.
86	</para>
87	</listitem>
88	</varlistentry>
89	<varlistentry>
90	<term><parameter>params</parameter></term>
91	<listitem>
92	<para>
93	Specifies a pointer to the value or values that <parameter>params</parameter> will be set to.
94	</para>
95	</listitem>
96	</varlistentry>
97	</variablelist>
98	</refsect1>
99	<refsect1 id="description"><title>Description</title>
100	<para>
101	<function>glLightModel</function> sets the lighting model parameter.
102	<parameter>pname</parameter> names a parameter and <parameter>params</parameter> gives the new value.
103	There are three lighting model parameters:
104	</para>
105	<variablelist>
106	<varlistentry>
107	<term><constant>GL_LIGHT_MODEL_AMBIENT</constant></term>
108	<listitem>
109	<para>
110	</para>
111	<para>
112	<parameter>params</parameter> contains four integer or floating-point values that specify
113	the ambient RGBA intensity of the entire scene.
114	Integer values are mapped linearly such that the most positive representable
115	value maps to 1.0,
116	and the most negative representable value maps to
117	<inlineequation><mml:math>
118	<!-- eqn: -1.0:-->
119	<mml:mn>-1.0</mml:mn>
120	</mml:math></inlineequation>.
121	Floating-point values are mapped directly.
122	Neither integer nor floating-point values are clamped.
123	The initial ambient scene intensity is (0.2, 0.2, 0.2, 1.0).
124	</para>
125	</listitem>
126	</varlistentry>
127	<varlistentry>
128	<term><constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant></term>
129	<listitem>
130	<para>
131	</para>
132	<para>
133	<parameter>params</parameter> must be either <constant>GL_SEPARATE_SPECULAR_COLOR</constant> or
134	<constant>GL_SINGLE_COLOR</constant>.
135	<constant>GL_SINGLE_COLOR</constant> specifies that a single color is generated from the
136	lighting computation for a vertex. <constant>GL_SEPARATE_SPECULAR_COLOR</constant>
137	specifies that the specular color computation of lighting be stored
138	separately from the remainder of the lighting computation. The specular
139	color is summed into the generated fragment's color after the application
140	of texture mapping (if enabled). The initial value is <constant>GL_SINGLE_COLOR</constant>.
141	</para>
142	</listitem>
143	</varlistentry>
144	<varlistentry>
145	<term><constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant></term>
146	<listitem>
147	<para>
148	</para>
149	<para>
150	<parameter>params</parameter> is a single integer or floating-point value that specifies
151	how specular reflection angles are computed.
152	If <parameter>params</parameter> is 0 (or 0.0), specular reflection angles take the
153	view direction to be parallel to and in the direction of the -<emphasis>z</emphasis> axis,
154	regardless of the location of the vertex in eye coordinates.
155	Otherwise, specular reflections are computed from the origin
156	of the eye coordinate system.
157	The initial value is 0.
158	</para>
159	</listitem>
160	</varlistentry>
161	<varlistentry>
162	<term><constant>GL_LIGHT_MODEL_TWO_SIDE</constant></term>
163	<listitem>
164	<para>
165	</para>
166	<para>
167	<parameter>params</parameter> is a single integer or floating-point value that specifies
168	whether one- or two-sided lighting calculations are done for polygons.
169	It has no effect on the lighting calculations for points,
170	lines,
171	or bitmaps.
172	If <parameter>params</parameter> is 0 (or 0.0), one-sided lighting is specified,
173	and only the <emphasis>front</emphasis> material parameters are used in the
174	lighting equation.
175	Otherwise, two-sided lighting is specified.
176	In this case, vertices of back-facing polygons are lighted using the
177	<emphasis>back</emphasis> material parameters
178	and have their normals reversed before the lighting equation is evaluated.
179	Vertices of front-facing polygons are always lighted using the
180	<emphasis>front</emphasis> material parameters,
181	with no change to their normals. The initial value is 0.
182	</para>
183	</listitem>
184	</varlistentry>
185	</variablelist>
186	<para>
187	In RGBA mode, the lighted color of a vertex is the sum of
188	the material emission intensity,
189	the product of the material ambient reflectance and the lighting model full-scene
190	ambient intensity,
191	and the contribution of each enabled light source.
192	Each light source contributes the sum of three terms:
193	ambient, diffuse, and specular.
194	The ambient light source contribution is the product of the material ambient
195	reflectance and the light's ambient intensity.
196	The diffuse light source contribution is the product of the material diffuse
197	reflectance,
198	the light's diffuse intensity,
199	and the dot product of the vertex's normal with the normalized vector from
200	the vertex to the light source.
201	The specular light source contribution is the product of the material specular
202	reflectance,
203	the light's specular intensity,
204	and the dot product of the normalized vertex-to-eye and vertex-to-light
205	vectors,
206	raised to the power of the shininess of the material.
207	All three light source contributions are attenuated equally based on
208	the distance from the vertex to the light source and on light source
209	direction, spread exponent, and spread cutoff angle.
210	All dot products are replaced with 0 if they evaluate to a negative value.
211	</para>
212	<para>
213	The alpha component of the resulting lighted color is set to the alpha value
214	of the material diffuse reflectance.
215	</para>
216	<para>
217	In color index mode,
218	the value of the lighted index of a vertex ranges from the ambient
219	to the specular values passed to <citerefentry><refentrytitle>glMaterial</refentrytitle></citerefentry> using <constant>GL_COLOR_INDEXES</constant>.
220	Diffuse and specular coefficients,
221	computed with a (.30, .59, .11) weighting of the lights' colors,
222	the shininess of the material,
223	and the same reflection and attenuation equations as in the RGBA case,
224	determine how much above ambient the resulting index is.
225	</para>
226	</refsect1>
227	<refsect1 id="notes"><title>Notes</title>
228	<para>
229	<constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant> is available only if the GL version is
230	1.2 or greater.
231	</para>
232	</refsect1>
233	<refsect1 id="errors"><title>Errors</title>
234	<para>
235	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is not an accepted value.
236	</para>
237	<para>
238	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is
239	<constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant> and <parameter>params</parameter> is not one of
240	<constant>GL_SINGLE_COLOR</constant> or <constant>GL_SEPARATE_SPECULAR_COLOR</constant>.
241	</para>
242	<para>
243	<constant>GL_INVALID_OPERATION</constant> is generated if <function>glLightModel</function> is executed between
244	the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
245	</para>
246	</refsect1>
247	<refsect1 id="associatedgets"><title>Associated Gets</title>
248	<para>
249	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_AMBIENT</constant>
250	</para>
251	<para>
252	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_COLOR_CONTROL</constant>
253	</para>
254	<para>
255	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_LOCAL_VIEWER</constant>
256	</para>
257	<para>
258	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LIGHT_MODEL_TWO_SIDE</constant>
259	</para>
260	<para>
261	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_LIGHTING</constant>
262	</para>
263	</refsect1>
264	<refsect1 id="seealso"><title>See Also</title>
265	<para>
266	<citerefentry><refentrytitle>glLight</refentrytitle></citerefentry>,
267	<citerefentry><refentrytitle>glMaterial</refentrytitle></citerefentry>
268	</para>
269	</refsect1>
270	<refsect1 id="Copyright"><title>Copyright</title>
271	<para>
272	Copyright <trademark class="copyright"></trademark> 1991-2006
273	Silicon Graphics, Inc. This document is licensed under the SGI
274	Free Software B License. For details, see
275	<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
276	</para>
277	</refsect1>
278	</refentry>