| 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="glLogicOp"> |
| 5 | <refmeta> |
| 6 | <refmetainfo> |
| 7 | <copyright> |
| 8 | <year>1991-2006</year> |
| 9 | <holder>Silicon Graphics, Inc.</holder> |
| 10 | </copyright> |
| 11 | </refmetainfo> |
| 12 | <refentrytitle>glLogicOp</refentrytitle> |
| 13 | <manvolnum>3G</manvolnum> |
| 14 | </refmeta> |
| 15 | <refnamediv> |
| 16 | <refname>glLogicOp</refname> |
| 17 | <refpurpose>specify a logical pixel operation for rendering</refpurpose> |
| 18 | </refnamediv> |
| 19 | <refsynopsisdiv><title>C Specification</title> |
| 20 | <funcsynopsis> |
| 21 | <funcprototype> |
| 22 | <funcdef>void <function>glLogicOp</function></funcdef> |
| 23 | <paramdef>GLenum <parameter>opcode</parameter></paramdef> |
| 24 | </funcprototype> |
| 25 | </funcsynopsis> |
| 26 | </refsynopsisdiv> |
| 27 | <refsect1 id="parameters"><title>Parameters</title> |
| 28 | <variablelist> |
| 29 | <varlistentry> |
| 30 | <term><parameter>opcode</parameter></term> |
| 31 | <listitem> |
| 32 | <para> |
| 33 | Specifies a symbolic constant that selects a logical operation. |
| 34 | The following symbols are accepted: |
| 35 | <constant>GL_CLEAR</constant>, |
| 36 | <constant>GL_SET</constant>, |
| 37 | <constant>GL_COPY</constant>, |
| 38 | <constant>GL_COPY_INVERTED</constant>, |
| 39 | <constant>GL_NOOP</constant>, |
| 40 | <constant>GL_INVERT</constant>, |
| 41 | <constant>GL_AND</constant>, |
| 42 | <constant>GL_NAND</constant>, |
| 43 | <constant>GL_OR</constant>, |
| 44 | <constant>GL_NOR</constant>, |
| 45 | <constant>GL_XOR</constant>, |
| 46 | <constant>GL_EQUIV</constant>, |
| 47 | <constant>GL_AND_REVERSE</constant>, |
| 48 | <constant>GL_AND_INVERTED</constant>, |
| 49 | <constant>GL_OR_REVERSE</constant>, and |
| 50 | <constant>GL_OR_INVERTED</constant>. The initial value is <constant>GL_COPY</constant>. |
| 51 | </para> |
| 52 | </listitem> |
| 53 | </varlistentry> |
| 54 | </variablelist> |
| 55 | </refsect1> |
| 56 | <refsect1 id="description"><title>Description</title> |
| 57 | <para> |
| 58 | <function>glLogicOp</function> specifies a logical operation that, |
| 59 | when enabled, |
| 60 | is applied between the incoming RGBA color |
| 61 | and the RGBA color at the corresponding location in the |
| 62 | frame buffer. |
| 63 | To enable or disable the logical operation, call |
| 64 | <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> |
| 65 | using the symbolic constant <constant>GL_COLOR_LOGIC_OP</constant>. The initial value is |
| 66 | disabled. |
| 67 | </para> |
| 68 | <para> |
| 69 | </para> |
| 70 | <informaltable frame="topbot"> |
| 71 | <tgroup cols="2" align="left"> |
| 72 | <colspec/> |
| 73 | <colspec/> |
| 74 | <thead> |
| 75 | <row> |
| 76 | <entry rowsep="1" align="left"><emphasis role="bold"> |
| 77 | Opcode |
| 78 | </emphasis></entry> |
| 79 | <entry rowsep="1" align="left"><emphasis role="bold"> |
| 80 | Resulting Operation |
| 81 | </emphasis></entry> |
| 82 | </row> |
| 83 | </thead> |
| 84 | <tbody> |
| 85 | <row> |
| 86 | <entry align="left"> |
| 87 | <constant>GL_CLEAR</constant> |
| 88 | </entry> |
| 89 | <entry align="center"> |
| 90 | 0 |
| 91 | </entry> |
| 92 | </row> |
| 93 | <row> |
| 94 | <entry align="left"> |
| 95 | <constant>GL_SET</constant> |
| 96 | </entry> |
| 97 | <entry align="center"> |
| 98 | 1 |
| 99 | </entry> |
| 100 | </row> |
| 101 | <row> |
| 102 | <entry align="left"> |
| 103 | <constant>GL_COPY</constant> |
| 104 | </entry> |
| 105 | <entry align="center"> |
| 106 | s |
| 107 | </entry> |
| 108 | </row> |
| 109 | <row> |
| 110 | <entry align="left"> |
| 111 | <constant>GL_COPY_INVERTED</constant> |
| 112 | </entry> |
| 113 | <entry align="center"> |
| 114 | ~s |
| 115 | </entry> |
| 116 | </row> |
| 117 | <row> |
| 118 | <entry align="left"> |
| 119 | <constant>GL_NOOP</constant> |
| 120 | </entry> |
| 121 | <entry align="center"> |
| 122 | d |
| 123 | </entry> |
| 124 | </row> |
| 125 | <row> |
| 126 | <entry align="left"> |
| 127 | <constant>GL_INVERT</constant> |
| 128 | </entry> |
| 129 | <entry align="center"> |
| 130 | ~d |
| 131 | </entry> |
| 132 | </row> |
| 133 | <row> |
| 134 | <entry align="left"> |
| 135 | <constant>GL_AND</constant> |
| 136 | </entry> |
| 137 | <entry align="center"> |
| 138 | s & d |
| 139 | </entry> |
| 140 | </row> |
| 141 | <row> |
| 142 | <entry align="left"> |
| 143 | <constant>GL_NAND</constant> |
| 144 | </entry> |
| 145 | <entry align="center"> |
| 146 | ~(s & d) |
| 147 | </entry> |
| 148 | </row> |
| 149 | <row> |
| 150 | <entry align="left"> |
| 151 | <constant>GL_OR</constant> |
| 152 | </entry> |
| 153 | <entry align="center"> |
| 154 | s | d |
| 155 | </entry> |
| 156 | </row> |
| 157 | <row> |
| 158 | <entry align="left"> |
| 159 | <constant>GL_NOR</constant> |
| 160 | </entry> |
| 161 | <entry align="center"> |
| 162 | ~(s | d) |
| 163 | </entry> |
| 164 | </row> |
| 165 | <row> |
| 166 | <entry align="left"> |
| 167 | <constant>GL_XOR</constant> |
| 168 | </entry> |
| 169 | <entry align="center"> |
| 170 | s ^ d |
| 171 | </entry> |
| 172 | </row> |
| 173 | <row> |
| 174 | <entry align="left"> |
| 175 | <constant>GL_EQUIV</constant> |
| 176 | </entry> |
| 177 | <entry align="center"> |
| 178 | ~(s ^ d) |
| 179 | </entry> |
| 180 | </row> |
| 181 | <row> |
| 182 | <entry align="left"> |
| 183 | <constant>GL_AND_REVERSE</constant> |
| 184 | </entry> |
| 185 | <entry align="center"> |
| 186 | s & ~d |
| 187 | </entry> |
| 188 | </row> |
| 189 | <row> |
| 190 | <entry align="left"> |
| 191 | <constant>GL_AND_INVERTED</constant> |
| 192 | </entry> |
| 193 | <entry align="center"> |
| 194 | ~s & d |
| 195 | </entry> |
| 196 | </row> |
| 197 | <row> |
| 198 | <entry align="left"> |
| 199 | <constant>GL_OR_REVERSE</constant> |
| 200 | </entry> |
| 201 | <entry align="center"> |
| 202 | s | ~d |
| 203 | </entry> |
| 204 | </row> |
| 205 | <row> |
| 206 | <entry align="left"> |
| 207 | <constant>GL_OR_INVERTED</constant> |
| 208 | </entry> |
| 209 | <entry align="center"> |
| 210 | ~s | d |
| 211 | </entry> |
| 212 | </row> |
| 213 | </tbody> |
| 214 | </tgroup> |
| 215 | </informaltable> |
| 216 | <para> |
| 217 | <parameter>opcode</parameter> is a symbolic constant chosen from the list above. |
| 218 | In the explanation of the logical operations, |
| 219 | <emphasis>s</emphasis> represents the incoming color and |
| 220 | <emphasis>d</emphasis> represents the color in the frame buffer. |
| 221 | Standard C-language operators are used. |
| 222 | As these bitwise operators suggest, |
| 223 | the logical operation is applied independently to each bit pair of the |
| 224 | source and destination colors. |
| 225 | </para> |
| 226 | </refsect1> |
| 227 | <refsect1 id="notes"><title>Notes</title> |
| 228 | <para> |
| 229 | When more than one RGBA color buffer is enabled for drawing, |
| 230 | logical operations are performed separately for each enabled buffer, |
| 231 | using for the destination value the contents of that buffer |
| 232 | (see <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>). |
| 233 | </para> |
| 234 | <para> |
| 235 | Logic operations have no effect on floating point draw buffers. However, if |
| 236 | <constant>GL_COLOR_LOGIC_OP</constant> is enabled, blending is still disabled |
| 237 | in this case. |
| 238 | </para> |
| 239 | </refsect1> |
| 240 | <refsect1 id="errors"><title>Errors</title> |
| 241 | <para> |
| 242 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>opcode</parameter> is not an accepted value. |
| 243 | </para> |
| 244 | </refsect1> |
| 245 | <refsect1 id="associatedgets"><title>Associated Gets</title> |
| 246 | <para> |
| 247 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LOGIC_OP_MODE</constant>. |
| 248 | </para> |
| 249 | <para> |
| 250 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_COLOR_LOGIC_OP</constant>. |
| 251 | </para> |
| 252 | </refsect1> |
| 253 | <refsect1 id="seealso"><title>See Also</title> |
| 254 | <para> |
| 255 | <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>, |
| 256 | <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>, |
| 257 | <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, |
| 258 | <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry> |
| 259 | </para> |
| 260 | </refsect1> |
| 261 | <refsect1 id="Copyright"><title>Copyright</title> |
| 262 | <para> |
| 263 | Copyright <trademark class="copyright"></trademark> 1991-2006 |
| 264 | Silicon Graphics, Inc. This document is licensed under the SGI |
| 265 | Free Software B License. For details, see |
| 266 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. |
| 267 | </para> |
| 268 | </refsect1> |
| 269 | </refentry> |