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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="gluNurbsProperty"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>gluNurbsProperty</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>gluNurbsProperty</refname> | |
17 | <refpurpose>set a NURBS property</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>gluNurbsProperty</function></funcdef> | |
23 | <paramdef>GLUnurbs* <parameter>nurb</parameter></paramdef> | |
24 | <paramdef>GLenum <parameter>property</parameter></paramdef> | |
25 | <paramdef>GLfloat <parameter>value</parameter></paramdef> | |
26 | </funcprototype> | |
27 | </funcsynopsis> | |
28 | </refsynopsisdiv> | |
29 | <!-- eqn: ignoring delim $$ --> | |
30 | <refsect1 id="parameters"><title>Parameters</title> | |
31 | <variablelist> | |
32 | <varlistentry> | |
33 | <term><parameter>nurb</parameter></term> | |
34 | <listitem> | |
35 | <para> | |
36 | Specifies the NURBS object (created with <citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>). | |
37 | </para> | |
38 | </listitem> | |
39 | </varlistentry> | |
40 | <varlistentry> | |
41 | <term><parameter>property</parameter></term> | |
42 | <listitem> | |
43 | <para> | |
44 | Specifies the property to be set. Valid values are | |
45 | <constant>GLU_SAMPLING_TOLERANCE</constant>, | |
46 | <constant>GLU_DISPLAY_MODE</constant>, | |
47 | <constant>GLU_CULLING</constant>, | |
48 | <constant>GLU_AUTO_LOAD_MATRIX</constant>, | |
49 | <constant>GLU_PARAMETRIC_TOLERANCE</constant>, | |
50 | <constant>GLU_SAMPLING_METHOD</constant>, | |
51 | <constant>GLU_U_STEP</constant>, | |
52 | <constant>GLU_V_STEP</constant>, or | |
53 | <constant>GLU_NURBS_MODE</constant>. | |
54 | </para> | |
55 | </listitem> | |
56 | </varlistentry> | |
57 | <varlistentry> | |
58 | <term><parameter>value</parameter></term> | |
59 | <listitem> | |
60 | <para> | |
61 | Specifies the value of the indicated property. | |
62 | It may be a numeric value or one of | |
63 | <constant>GLU_OUTLINE_POLYGON</constant>, | |
64 | <constant>GLU_FILL</constant>, | |
65 | <constant>GLU_OUTLINE_PATCH</constant>, | |
66 | <constant>GLU_TRUE</constant>, | |
67 | <constant>GLU_FALSE</constant>, | |
68 | <constant>GLU_PATH_LENGTH</constant>, | |
69 | <constant>GLU_PARAMETRIC_ERROR</constant>, | |
70 | <constant>GLU_DOMAIN_DISTANCE</constant>, | |
71 | <constant>GLU_NURBS_RENDERER</constant>, or | |
72 | <constant>GLU_NURBS_TESSELLATOR</constant>. | |
73 | </para> | |
74 | </listitem> | |
75 | </varlistentry> | |
76 | </variablelist> | |
77 | </refsect1> | |
78 | <refsect1 id="description"><title>Description</title> | |
79 | <para> | |
80 | <function>gluNurbsProperty</function> is used to control properties stored in a NURBS object. These | |
81 | properties affect the way that a NURBS curve is rendered. The accepted | |
82 | values for <parameter>property</parameter> are as follows: | |
83 | </para> | |
84 | <variablelist> | |
85 | <varlistentry> | |
86 | <term><constant>GLU_NURBS_MODE</constant></term> | |
87 | <listitem> | |
88 | <para> | |
89 | <parameter>value</parameter> should be set to be either <constant>GLU_NURBS_RENDERER</constant> or | |
90 | <constant>GLU_NURBS_TESSELLATOR</constant>. When set to <constant>GLU_NURBS_RENDERER</constant>, NURBS objects | |
91 | are tessellated into OpenGL primitives and sent to the pipeline for | |
92 | rendering. When set to <constant>GLU_NURBS_TESSELLATOR</constant>, NURBS objects are | |
93 | tessellated into OpenGL primitives but the vertices, normals, colors, and/or textures are | |
94 | retrieved back through a callback interface (see <citerefentry><refentrytitle>gluNurbsCallback</refentrytitle></citerefentry>). This allows the user to cache the | |
95 | tessellated results for further processing. | |
96 | The initial value is <constant>GLU_NURBS_RENDERER</constant>. | |
97 | </para> | |
98 | </listitem> | |
99 | </varlistentry> | |
100 | <varlistentry> | |
101 | <term><constant>GLU_SAMPLING_METHOD</constant> </term> | |
102 | <listitem> | |
103 | <para> | |
104 | Specifies how a NURBS surface should be | |
105 | tessellated. | |
106 | <parameter>value</parameter> may be one of <constant>GLU_PATH_LENGTH</constant>, | |
107 | <constant>GLU_PARAMETRIC_ERROR</constant>, <constant>GLU_DOMAIN_DISTANCE</constant>, | |
108 | <constant>GLU_OBJECT_PATH_LENGTH</constant>, or | |
109 | <constant>GLU_OBJECT_PARAMETRIC_ERROR</constant>. | |
110 | When set to <constant>GLU_PATH_LENGTH</constant>, the surface is rendered so that | |
111 | the maximum length, in | |
112 | pixels, of the edges of the tessellation polygons is no greater than | |
113 | what is specified by <constant>GLU_SAMPLING_TOLERANCE</constant>. | |
114 | </para> | |
115 | <para> | |
116 | <constant>GLU_PARAMETRIC_ERROR</constant> specifies that the surface is rendered in such a | |
117 | way that the value specified by <constant>GLU_PARAMETRIC_TOLERANCE</constant> describes the | |
118 | maximum distance, in pixels, between the tessellation polygons and the | |
119 | surfaces they approximate. | |
120 | </para> | |
121 | <para> | |
122 | <constant>GLU_DOMAIN_DISTANCE</constant> allows users to specify, in parametric coordinates, | |
123 | how many sample points per unit length are taken in <emphasis>u</emphasis>, <emphasis>v</emphasis> | |
124 | direction. | |
125 | </para> | |
126 | <para> | |
127 | <constant>GLU_OBJECT_PATH_LENGTH</constant> is similar to <constant>GLU_PATH_LENGTH</constant> | |
128 | except that it is view independent; that is, the surface is rendered so that the maximum length, in object space, of edges of the tessellation polygons is no greater than what is specified by <constant>GLU_SAMPLING_TOLERANCE</constant>. | |
129 | </para> | |
130 | <para> | |
131 | <constant>GLU_OBJECT_PARAMETRIC_ERROR</constant> is similar to <constant>GLU_PARAMETRIC_ERROR</constant> except that it is view independent; that is, the surface is rendered in such a way that the value specified by <constant>GLU_PARAMETRIC_TOLERANCE</constant> describes the maximum distance, in object space, between the tessellation polygons and the surfaces they approximate. | |
132 | </para> | |
133 | <para> | |
134 | The initial value of <constant>GLU_SAMPLING_METHOD</constant> is <constant>GLU_PATH_LENGTH</constant>. | |
135 | </para> | |
136 | </listitem> | |
137 | </varlistentry> | |
138 | <varlistentry> | |
139 | <term><constant>GLU_SAMPLING_TOLERANCE</constant></term> | |
140 | <listitem> | |
141 | <para> | |
142 | Specifies the maximum length, in pixels or in object space length unit, | |
143 | to use when the sampling method is set to <constant>GLU_PATH_LENGTH</constant> or | |
144 | <constant>GLU_OBJECT_PATH_LENGTH</constant>. | |
145 | The NURBS code is conservative when rendering a curve | |
146 | or surface, so the actual length can be somewhat shorter. The initial | |
147 | value is 50.0 pixels. | |
148 | </para> | |
149 | </listitem> | |
150 | </varlistentry> | |
151 | <varlistentry> | |
152 | <term><constant>GLU_PARAMETRIC_TOLERANCE</constant></term> | |
153 | <listitem> | |
154 | <para> | |
155 | Specifies the maximum distance, in pixels or in object space length unit, | |
156 | to use when the sampling method is <constant>GLU_PARAMETRIC_ERROR</constant> or | |
157 | <constant>GLU_OBJECT_PARAMETRIC_ERROR</constant>. | |
158 | The initial value is 0.5. | |
159 | </para> | |
160 | </listitem> | |
161 | </varlistentry> | |
162 | <varlistentry> | |
163 | <term><constant>GLU_U_STEP</constant></term> | |
164 | <listitem> | |
165 | <para> | |
166 | Specifies the number of sample points per unit length taken | |
167 | along the <emphasis>u</emphasis> axis in parametric coordinates. It is needed when | |
168 | <constant>GLU_SAMPLING_METHOD</constant> is set to <constant>GLU_DOMAIN_DISTANCE</constant>. | |
169 | The initial value is 100. | |
170 | </para> | |
171 | </listitem> | |
172 | </varlistentry> | |
173 | <varlistentry> | |
174 | <term><constant>GLU_V_STEP</constant></term> | |
175 | <listitem> | |
176 | <para> | |
177 | Specifies the number of sample points per unit length taken | |
178 | along the <emphasis>v</emphasis> axis in parametric coordinate. It is needed when | |
179 | <constant>GLU_SAMPLING_METHOD</constant> is set to <constant>GLU_DOMAIN_DISTANCE</constant>. The initial | |
180 | value is 100. | |
181 | </para> | |
182 | </listitem> | |
183 | </varlistentry> | |
184 | <varlistentry> | |
185 | <term><constant>GLU_DISPLAY_MODE</constant></term> | |
186 | <listitem> | |
187 | <para> | |
188 | <parameter>value</parameter> can be set to | |
189 | <constant>GLU_OUTLINE_POLYGON</constant>, <constant>GLU_FILL</constant>, or | |
190 | <constant>GLU_OUTLINE_PATCH</constant>. | |
191 | When <constant>GLU_NURBS_MODE</constant> is set to be <constant>GLU_NURBS_RENDERER</constant>, | |
192 | <parameter>value</parameter> defines how a NURBS surface should be rendered. | |
193 | When <parameter>value</parameter> is set to <constant>GLU_FILL</constant>, the surface is rendered as a | |
194 | set of polygons. When <parameter>value</parameter> is set to | |
195 | <constant>GLU_OUTLINE_POLYGON</constant>, the NURBS library draws only the outlines | |
196 | of the polygons created by tessellation. When <parameter>value</parameter> is set to | |
197 | <constant>GLU_OUTLINE_PATCH</constant> just the outlines of patches and trim | |
198 | curves defined by the user are drawn. | |
199 | </para> | |
200 | <para> | |
201 | When <constant>GLU_NURBS_MODE</constant> is set to be <constant>GLU_NURBS_TESSELLATOR</constant>, | |
202 | <parameter>value</parameter> defines how a NURBS surface should be tessellated. | |
203 | When <constant>GLU_DISPLAY_MODE</constant> is set to <constant>GLU_FILL</constant> or | |
204 | <constant>GLU_OUTLINE_POLYGON</constant>, | |
205 | the NURBS surface is tessellated into OpenGL triangle primitives that can be | |
206 | retrieved back through callback functions. If <constant>GLU_DISPLAY_MODE</constant> is set to | |
207 | <constant>GLU_OUTLINE_PATCH</constant>, only the outlines of the patches and trim curves are generated as a sequence of line strips that can be retrieved back through callback functions. | |
208 | </para> | |
209 | <para> | |
210 | The initial value is <constant>GLU_FILL</constant>. | |
211 | </para> | |
212 | </listitem> | |
213 | </varlistentry> | |
214 | <varlistentry> | |
215 | <term><constant>GLU_CULLING</constant></term> | |
216 | <listitem> | |
217 | <para> | |
218 | <parameter>value</parameter> is a boolean value that, when set to <constant>GLU_TRUE</constant>, indicates that | |
219 | a NURBS curve should be discarded prior to tessellation if its control points | |
220 | lie outside the current viewport. The initial value is <constant>GLU_FALSE</constant>. | |
221 | </para> | |
222 | </listitem> | |
223 | </varlistentry> | |
224 | <varlistentry> | |
225 | <term><constant>GLU_AUTO_LOAD_MATRIX</constant></term> | |
226 | <listitem> | |
227 | <para> | |
228 | <parameter>value</parameter> is a boolean value. When set to <constant>GLU_TRUE</constant>, the NURBS code | |
229 | downloads the projection matrix, the modelview matrix, and the | |
230 | viewport from the GL server to compute sampling and | |
231 | culling | |
232 | matrices for each NURBS curve that is rendered. Sampling and culling matrices | |
233 | are required to determine the tessellation of a NURBS surface into line segments | |
234 | or polygons and to cull a NURBS surface if it lies outside the viewport. | |
235 | </para> | |
236 | <para> | |
237 | If this mode is set to <constant>GLU_FALSE</constant>, then the program needs | |
238 | to provide a projection matrix, a modelview matrix, and a viewport | |
239 | for the NURBS renderer to use to construct sampling and culling matrices. | |
240 | This can be done with the <citerefentry><refentrytitle>gluLoadSamplingMatrices</refentrytitle></citerefentry> function. | |
241 | This mode is initially set to <constant>GLU_TRUE</constant>. | |
242 | Changing it from <constant>GLU_TRUE</constant> to <constant>GLU_FALSE</constant> does not affect | |
243 | the sampling and culling matrices until | |
244 | <citerefentry><refentrytitle>gluLoadSamplingMatrices</refentrytitle></citerefentry> | |
245 | is called. | |
246 | </para> | |
247 | </listitem> | |
248 | </varlistentry> | |
249 | </variablelist> | |
250 | </refsect1> | |
251 | <refsect1 id="notes"><title>Notes</title> | |
252 | <para> | |
253 | If <constant>GLU_AUTO_LOAD_MATRIX</constant> is true, sampling and culling may be | |
254 | executed incorrectly if NURBS routines are compiled into a display list. | |
255 | </para> | |
256 | <para> | |
257 | A <parameter>property</parameter> of | |
258 | <constant>GLU_PARAMETRIC_TOLERANCE</constant>, | |
259 | <constant>GLU_SAMPLING_METHOD</constant>, | |
260 | <constant>GLU_U_STEP</constant>, or | |
261 | <constant>GLU_V_STEP</constant>, | |
262 | or a <parameter>value</parameter> of | |
263 | <constant>GLU_PATH_LENGTH</constant>, | |
264 | <constant>GLU_PARAMETRIC_ERROR</constant>, | |
265 | <constant>GLU_DOMAIN_DISTANCE</constant> | |
266 | are only available if the GLU version is 1.1 or greater. They are not | |
267 | valid parameters in GLU 1.0. | |
268 | </para> | |
269 | <para> | |
270 | <citerefentry><refentrytitle>gluGetString</refentrytitle></citerefentry> can | |
271 | be used to determine the GLU version. | |
272 | </para> | |
273 | <para> | |
274 | <constant>GLU_NURBS_MODE</constant> is only available if the GLU version is 1.3 or | |
275 | greater. | |
276 | </para> | |
277 | <para> | |
278 | The <constant>GLU_OBJECT_PATH_LENGTH</constant> and <constant>GLU_OBJECT_PARAMETRIC_ERROR</constant> | |
279 | values for the <constant>GLU_SAMPLING_METHOD</constant> property are only available if | |
280 | the GLU version is 1.3 or greater. | |
281 | </para> | |
282 | </refsect1> | |
283 | <refsect1 id="seealso"><title>See Also</title> | |
284 | <para> | |
285 | <citerefentry><refentrytitle>gluGetNurbsProperty</refentrytitle></citerefentry>, | |
286 | <citerefentry><refentrytitle>gluGetString</refentrytitle></citerefentry>, | |
287 | <citerefentry><refentrytitle>gluLoadSamplingMatrices</refentrytitle></citerefentry>, | |
288 | <citerefentry><refentrytitle>gluNewNurbsRenderer</refentrytitle></citerefentry>, | |
289 | <citerefentry><refentrytitle>gluNurbsCallback</refentrytitle></citerefentry> | |
290 | </para> | |
291 | </refsect1> | |
292 | <refsect1 id="Copyright"><title>Copyright</title> | |
293 | <para> | |
294 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
295 | Silicon Graphics, Inc. This document is licensed under the SGI | |
296 | Free Software B License. For details, see | |
297 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
298 | </para> | |
299 | </refsect1> | |
300 | </refentry> |