upstream-man-pages/man2/xhtml/glPointSize.xml

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   3 <?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>glPointSize</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glPointSize"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glPointSize — specify the diameter of rasterized points</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">glPointSize</b>(</code></td><td>GLfloat  </td><td><var class="pdparam">size</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>size</code></em></span></dt><dd><p>
   4                     Specifies the diameter of rasterized points.
   5                     The initial value is 1.
   6                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
   7             <code class="function">glPointSize</code> specifies the rasterized diameter of both aliased and antialiased
   8             points.  Using a point size other than 1 has different effects, depending
   9             on whether point antialiasing is enabled.  To enable and disable point
  10             antialiasing, call <a class="citerefentry" href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and <a class="citerefentry" href="glDisable.xml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a> with argument
  11             <code class="constant">GL_POINT_SMOOTH</code>. Point antialiasing is initially disabled.
  12         </p><p>
  13             The specified point size is multiplied with a distance attenuation factor
  14             and clamped to the specified point size range, and further clamped to the
  15             implementation-dependent point size range to produce the derived point size
  16             using
  17         </p><p>
  18             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  19
  20                 <mml:mrow>
  21                     <mml:mi mathvariant="italic">pointSize</mml:mi>
  22                     <mml:mo>=</mml:mo>
  23                     <mml:mrow>
  24                         <mml:mi mathvariant="italic">clamp</mml:mi>
  25                         <mml:mo>⁢</mml:mo>
  26                         <mml:mfenced open="(" close=")">
  27                             <mml:mrow>
  28                                 <mml:mi mathvariant="italic">size</mml:mi>
  29                                 <mml:mo>×</mml:mo>
  30                                 <mml:msqrt>
  31                                     <mml:mfenced open="" close="">
  32                                         <mml:mfenced open="(" close=")">
  33                                             <mml:mfrac>
  34                                                 <mml:mn>1</mml:mn>
  35                                                 <mml:mfenced open="" close="">
  36                                                     <mml:mrow>
  37                                                         <mml:mi mathvariant="italic">a</mml:mi>
  38                                                         <mml:mo>+</mml:mo>
  39                                                         <mml:mrow>
  40                                                             <mml:mi mathvariant="italic">b</mml:mi>
  41                                                             <mml:mo>×</mml:mo>
  42                                                             <mml:mi mathvariant="italic">d</mml:mi>
  43                                                         </mml:mrow>
  44                                                         <mml:mo>+</mml:mo>
  45                                                         <mml:mrow>
  46                                                             <mml:mi mathvariant="italic">c</mml:mi>
  47                                                             <mml:mo>×</mml:mo>
  48                                                             <mml:mfenced open="" close="">
  49                                                                 <mml:msup><mml:mi mathvariant="italic">d</mml:mi>
  50                                                                 <mml:mn>2</mml:mn>
  51                                                                 </mml:msup>
  52                                                             </mml:mfenced>
  53                                                         </mml:mrow>
  54                                                     </mml:mrow>
  55                                                 </mml:mfenced>
  56                                             </mml:mfrac>
  57                                         </mml:mfenced>
  58                                     </mml:mfenced>
  59                                 </mml:msqrt>
  60                             </mml:mrow>
  61                         </mml:mfenced>
  62                     </mml:mrow>
  63                 </mml:mrow>
  64             </mml:math></div><p>
  65         </p><p>
  66             where
  67             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">d</mml:mi></mml:math>
  68             is the eye-coordinate distance from the eye to the vertex, and
  69             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">a</mml:mi></mml:math>,
  70             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">b</mml:mi></mml:math>,
  71             and
  72             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">c</mml:mi></mml:math>
  73             are the distance attenuation coefficients (see
  74             <a class="citerefentry" href="glPointParameter.xml"><span class="citerefentry"><span class="refentrytitle">glPointParameter</span></span></a>).
  75         </p><p>
  76             If multisampling is disabled, the computed point size is used as the
  77             point's width.
  78         </p><p>
  79             If multisampling is enabled, the point may be faded by modifying the point
  80             alpha value (see <a class="citerefentry" href="glSampleCoverage.xml"><span class="citerefentry"><span class="refentrytitle">glSampleCoverage</span></span></a>) instead of allowing the point width
  81             to go below a given threshold (see <a class="citerefentry" href="glPointParameter.xml"><span class="citerefentry"><span class="refentrytitle">glPointParameter</span></span></a>).  In this case,
  82             the width is further modified in the following manner:
  83         </p><p>
  84             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  85
  86                 <mml:mrow>
  87                     <mml:mi mathvariant="italic">pointWidth</mml:mi>
  88                     <mml:mo>=</mml:mo>
  89                     <mml:mfenced open="{" close="">
  90                         <mml:mrow>
  91                             <mml:mtable>
  92                                 <mml:mtr><mml:mtd>
  93                                     <mml:mi mathvariant="italic">pointSize</mml:mi>
  94                                 </mml:mtd></mml:mtr>
  95                                 <mml:mtr><mml:mtd>
  96                                     <mml:mi mathvariant="italic">threshold</mml:mi>
  97                                 </mml:mtd></mml:mtr>
  98                             </mml:mtable>
  99                             <mml:mo>⁢</mml:mo>
 100                             <mml:mtable>
 101                                 <mml:mtr><mml:mtd>
 102                                     <mml:mrow>
 103                                         <mml:mi mathvariant="italic">pointSize</mml:mi>
 104                                         <mml:mo>&gt;=</mml:mo>
 105                                         <mml:mi mathvariant="italic">threshold</mml:mi>
 106                                     </mml:mrow>
 107                                 </mml:mtd></mml:mtr>
 108                                 <mml:mtr><mml:mtd>
 109                                     <mml:mi mathvariant="italic">otherwise</mml:mi>
 110                                 </mml:mtd></mml:mtr>
 111                             </mml:mtable>
 112                         </mml:mrow>
 113                     </mml:mfenced>
 114                 </mml:mrow>
 115             </mml:math></div><p>
 116         </p><p>
 117             The point alpha value is modified by computing:
 118         </p><p>
 119             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 120
 121                 <mml:mrow>
 122                     <mml:mi mathvariant="italic">pointAlpha</mml:mi>
 123                     <mml:mo>=</mml:mo>
 124                     <mml:mfenced open="{" close="">
 125                         <mml:mrow>
 126                             <mml:mtable>
 127                                 <mml:mtr><mml:mtd>
 128                                     <mml:mn>1</mml:mn>
 129                                 </mml:mtd></mml:mtr>
 130                                 <mml:mtr><mml:mtd>
 131                                     <mml:msup><mml:mfenced open="(" close=")">
 132                                         <mml:mfrac>
 133                                             <mml:mi mathvariant="italic">pointSize</mml:mi>
 134                                             <mml:mi mathvariant="italic">threshold</mml:mi>
 135                                         </mml:mfrac>
 136                                     </mml:mfenced>
 137                                     <mml:mn>2</mml:mn>
 138                                     </mml:msup>
 139                                 </mml:mtd></mml:mtr>
 140                             </mml:mtable>
 141                             <mml:mo>⁢</mml:mo>
 142                             <mml:mtable>
 143                                 <mml:mtr><mml:mtd>
 144                                     <mml:mrow>
 145                                         <mml:mi mathvariant="italic">pointSize</mml:mi>
 146                                         <mml:mo>&gt;=</mml:mo>
 147                                         <mml:mi mathvariant="italic">threshold</mml:mi>
 148                                     </mml:mrow>
 149                                 </mml:mtd></mml:mtr>
 150                                 <mml:mtr><mml:mtd>
 151                                     <mml:mi mathvariant="italic">otherwise</mml:mi>
 152                                 </mml:mtd></mml:mtr>
 153                             </mml:mtable>
 154                         </mml:mrow>
 155                     </mml:mfenced>
 156                 </mml:mrow>
 157             </mml:math></div><p>
 158         </p><p>
 159             If point antialiasing is disabled, the actual size is determined by
 160             rounding the supplied size to the nearest integer.  (If the rounding
 161             results in the value 0, it is as if the point size were 1.)  If the rounded
 162             size is odd, then the center point
 163             (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 164
 165                 <mml:mi mathvariant="italic">x</mml:mi>
 166             </mml:math>,
 167             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 168
 169                 <mml:mi mathvariant="italic">y</mml:mi>
 170             </mml:math>)
 171             of the pixel fragment
 172             that represents the point is computed as
 173         </p><p>
 174             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 175
 176                 <mml:mfenced open="(" close=")">
 177                     <mml:mrow>
 178                         <mml:mfenced open="&#x230A;" close="&#x230B;">
 179                             <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 180                             <mml:mi mathvariant="italic">w</mml:mi>
 181                             </mml:msub>
 182                         </mml:mfenced>
 183                         <mml:mo>+</mml:mo>
 184                         <mml:mn>.5</mml:mn>
 185                     </mml:mrow>
 186                     <mml:mrow>
 187                         <mml:mfenced open="&#x230A;" close="&#x230B;">
 188                             <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 189                             <mml:mi mathvariant="italic">w</mml:mi>
 190                             </mml:msub>
 191                         </mml:mfenced>
 192                         <mml:mo>+</mml:mo>
 193                         <mml:mn>.5</mml:mn>
 194                     </mml:mrow>
 195                 </mml:mfenced>
 196             </mml:math>
 197         </p><p>
 198             where
 199             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">w</mml:mi></mml:math>
 200             subscripts indicate window coordinates.  All pixels that lie
 201             within the square grid of the rounded size centered at
 202             (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 203
 204                 <mml:mi mathvariant="italic">x</mml:mi>
 205             </mml:math>,
 206             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 207
 208                 <mml:mi mathvariant="italic">y</mml:mi>
 209             </mml:math>)
 210             make
 211             up the fragment.  If the size is even, the center point is
 212         </p><p>
 213             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 214
 215                 <mml:mfenced open="(" close=")">
 216                     <mml:mfenced open="&#x230A;" close="&#x230B;">
 217                         <mml:mrow>
 218                             <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 219                             <mml:mi mathvariant="italic">w</mml:mi>
 220                             </mml:msub>
 221                             <mml:mo>+</mml:mo>
 222                             <mml:mn>.5</mml:mn>
 223                         </mml:mrow>
 224                     </mml:mfenced>
 225                     <mml:mfenced open="&#x230A;" close="&#x230B;">
 226                         <mml:mrow>
 227                             <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 228                             <mml:mi mathvariant="italic">w</mml:mi>
 229                             </mml:msub>
 230                             <mml:mo>+</mml:mo>
 231                             <mml:mn>.5</mml:mn>
 232                         </mml:mrow>
 233                     </mml:mfenced>
 234                 </mml:mfenced>
 235             </mml:math>
 236         </p><p>
 237             and the rasterized fragment's centers are the half-integer window
 238             coordinates within the square of the rounded size centered at
 239             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 240
 241                 <mml:mfenced open="(" close=")">
 242                     <mml:mi mathvariant="italic">x</mml:mi>
 243                     <mml:mi mathvariant="italic">y</mml:mi>
 244                 </mml:mfenced>
 245             </mml:math>.
 246             All pixel fragments produced in rasterizing a nonantialiased point are
 247             assigned the same associated data, that of the vertex corresponding to the
 248             point.
 249         </p><p>
 250             If antialiasing is enabled, then point rasterization produces a fragment
 251             for each pixel square that intersects the region lying within the circle
 252             having diameter equal to the current point size and centered at the point's
 253             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 254
 255                 <mml:mfenced open="(" close=")">
 256                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 257                     <mml:mi mathvariant="italic">w</mml:mi>
 258                     </mml:msub>
 259                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 260                     <mml:mi mathvariant="italic">w</mml:mi>
 261                     </mml:msub>
 262                 </mml:mfenced>
 263             </mml:math>.
 264             The coverage value for each fragment is the
 265             window coordinate area of the intersection of the circular region with the
 266             corresponding pixel square.  This value is saved and used in the final
 267             rasterization step.  The data associated with each fragment is the data
 268             associated with the point being rasterized.
 269         </p><p>
 270             Not all sizes are supported when point antialiasing is enabled.  If an
 271             unsupported size is requested, the nearest supported size is used.  Only
 272             size 1 is guaranteed to be supported; others depend on the implementation.
 273             To query the range of supported sizes and the size difference between
 274             supported sizes within the range, call <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with arguments
 275             <code class="constant">GL_SMOOTH_POINT_SIZE_RANGE</code> and <code class="constant">GL_SMOOTH_POINT_SIZE_GRANULARITY</code>.
 276             For aliased points, query the supported ranges and granularity with
 277             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with arguments <code class="constant">GL_ALIASED_POINT_SIZE_RANGE</code>.
 278         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
 279             The point size specified by <code class="function">glPointSize</code> is always returned when
 280             <code class="constant">GL_POINT_SIZE</code> is queried.  Clamping and rounding for aliased and
 281             antialiased points have no effect on the specified value.
 282         </p><p>
 283             A non-antialiased point size may be clamped to an implementation-dependent
 284             maximum.  Although this maximum cannot be queried, it must be no less than
 285             the maximum value for antialiased points, rounded to the nearest integer
 286             value.
 287         </p><p>
 288             <code class="constant">GL_POINT_SIZE_RANGE</code> and <code class="constant">GL_POINT_SIZE_GRANULARITY</code> are
 289             deprecated in GL versions 1.2 and greater.  Their functionality has been
 290             replaced by <code class="constant">GL_SMOOTH_POINT_SIZE_RANGE</code> and
 291             <code class="constant">GL_SMOOTH_POINT_SIZE_GRANULARITY</code>.
 292         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 293             <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>size</code></em> is less than or equal to 0.
 294         </p><p>
 295             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glPointSize</code>
 296             is executed between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
 297             and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 298         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 299             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_ALIASED_POINT_SIZE_RANGE</code>
 300         </p><p>
 301             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_POINT_SIZE</code>
 302         </p><p>
 303             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_POINT_SIZE_MIN</code>
 304         </p><p>
 305             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_POINT_SIZE_MAX</code>
 306         </p><p>
 307             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_POINT_FADE_THRESHOLD_SIZE</code>
 308         </p><p>
 309             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_POINT_DISTANCE_ATTENUATION</code>
 310         </p><p>
 311             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SMOOTH_POINT_SIZE_RANGE</code>
 312         </p><p>
 313             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SMOOTH_POINT_SIZE_GRANULARITY</code>
 314         </p><p>
 315             <a class="citerefentry" href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_POINT_SMOOTH</code>
 316         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 317             <a class="citerefentry" href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>,
 318             <a class="citerefentry" href="glPointParameter.xml"><span class="citerefentry"><span class="refentrytitle">glPointParameter</span></span></a>
 319         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 320             Copyright <span class="trademark"></span>© 1991-2006
 321             Silicon Graphics, Inc. This document is licensed under the SGI
 322             Free Software B License. For details, see
 323             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 324         </p></div></div></body></html>