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="glBlendFunc"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glBlendFunc</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glBlendFunc</refname> | |
17 | <refpurpose>specify pixel arithmetic</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glBlendFunc</function></funcdef> | |
23 | <paramdef>GLenum <parameter>sfactor</parameter></paramdef> | |
24 | <paramdef>GLenum <parameter>dfactor</parameter></paramdef> | |
25 | </funcprototype> | |
26 | </funcsynopsis> | |
27 | </refsynopsisdiv> | |
28 | <!-- eqn: ignoring delim $$ --> | |
29 | <refsect1 id="parameters"><title>Parameters</title> | |
30 | <variablelist> | |
31 | <varlistentry> | |
32 | <term><parameter>sfactor</parameter></term> | |
33 | <listitem> | |
34 | <para> | |
35 | Specifies how the red, green, blue, | |
36 | and alpha source blending factors are computed. | |
37 | The following symbolic constants are accepted: | |
38 | <constant>GL_ZERO</constant>, | |
39 | <constant>GL_ONE</constant>, | |
40 | <constant>GL_SRC_COLOR</constant>, | |
41 | <constant>GL_ONE_MINUS_SRC_COLOR</constant>, | |
42 | <constant>GL_DST_COLOR</constant>, | |
43 | <constant>GL_ONE_MINUS_DST_COLOR</constant>, | |
44 | <constant>GL_SRC_ALPHA</constant>, | |
45 | <constant>GL_ONE_MINUS_SRC_ALPHA</constant>, | |
46 | <constant>GL_DST_ALPHA</constant>, | |
47 | <constant>GL_ONE_MINUS_DST_ALPHA</constant>, | |
48 | <constant>GL_CONSTANT_COLOR</constant>, | |
49 | <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>, | |
50 | <constant>GL_CONSTANT_ALPHA</constant>, | |
51 | <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>, and | |
52 | <constant>GL_SRC_ALPHA_SATURATE</constant>. | |
53 | The initial value is <constant>GL_ONE</constant>. | |
54 | </para> | |
55 | </listitem> | |
56 | </varlistentry> | |
57 | <varlistentry> | |
58 | <term><parameter>dfactor</parameter></term> | |
59 | <listitem> | |
60 | <para> | |
61 | Specifies how the red, green, blue, | |
62 | and alpha destination blending factors are computed. | |
63 | The following symbolic constants are accepted: | |
64 | <constant>GL_ZERO</constant>, | |
65 | <constant>GL_ONE</constant>, | |
66 | <constant>GL_SRC_COLOR</constant>, | |
67 | <constant>GL_ONE_MINUS_SRC_COLOR</constant>, | |
68 | <constant>GL_DST_COLOR</constant>, | |
69 | <constant>GL_ONE_MINUS_DST_COLOR</constant>, | |
70 | <constant>GL_SRC_ALPHA</constant>, | |
71 | <constant>GL_ONE_MINUS_SRC_ALPHA</constant>, | |
72 | <constant>GL_DST_ALPHA</constant>, | |
73 | <constant>GL_ONE_MINUS_DST_ALPHA</constant>. | |
74 | <constant>GL_CONSTANT_COLOR</constant>, | |
75 | <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>, | |
76 | <constant>GL_CONSTANT_ALPHA</constant>, and | |
77 | <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>. | |
78 | The initial value is <constant>GL_ZERO</constant>. | |
79 | </para> | |
80 | </listitem> | |
81 | </varlistentry> | |
82 | </variablelist> | |
83 | </refsect1> | |
84 | <refsect1 id="description"><title>Description</title> | |
85 | <para> | |
86 | In RGBA mode, pixels can be drawn using a function that blends | |
87 | the incoming (source) RGBA values with the RGBA values | |
88 | that are already in the frame buffer (the destination values). | |
89 | Blending is initially disabled. | |
90 | Use <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument <constant>GL_BLEND</constant> | |
91 | to enable and disable blending. | |
92 | </para> | |
93 | <para> | |
94 | <function>glBlendFunc</function> defines the operation of blending when it is enabled. | |
95 | <parameter>sfactor</parameter> specifies which method is used to scale the | |
96 | source color components. | |
97 | <parameter>dfactor</parameter> specifies which method is used to scale the | |
98 | destination color components. | |
99 | The possible methods are described in the following table. | |
100 | Each method defines four scale factors, | |
101 | one each for red, green, blue, and alpha. | |
102 | In the table and in subsequent equations, source and destination | |
103 | color components are referred to as | |
104 | <inlineequation><mml:math> | |
105 | <!-- eqn: ( R sub s , G sub s , B sub s , A sub s ):--> | |
106 | <mml:mfenced open="(" close=")"> | |
107 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
108 | <mml:mi mathvariant="italic">s</mml:mi> | |
109 | </mml:msub> | |
110 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
111 | <mml:mi mathvariant="italic">s</mml:mi> | |
112 | </mml:msub> | |
113 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
114 | <mml:mi mathvariant="italic">s</mml:mi> | |
115 | </mml:msub> | |
116 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
117 | <mml:mi mathvariant="italic">s</mml:mi> | |
118 | </mml:msub> | |
119 | </mml:mfenced> | |
120 | </mml:math></inlineequation> | |
121 | and | |
122 | <inlineequation><mml:math> | |
123 | <!-- eqn: ( R sub d , G sub d , B sub d , A sub d ):--> | |
124 | <mml:mfenced open="(" close=")"> | |
125 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
126 | <mml:mi mathvariant="italic">d</mml:mi> | |
127 | </mml:msub> | |
128 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
129 | <mml:mi mathvariant="italic">d</mml:mi> | |
130 | </mml:msub> | |
131 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
132 | <mml:mi mathvariant="italic">d</mml:mi> | |
133 | </mml:msub> | |
134 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
135 | <mml:mi mathvariant="italic">d</mml:mi> | |
136 | </mml:msub> | |
137 | </mml:mfenced> | |
138 | </mml:math></inlineequation>. | |
139 | The color specified by <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry> is referred to as | |
140 | <inlineequation><mml:math> | |
141 | <!-- eqn: ( R sub c , G sub c , B sub c , A sub c ):--> | |
142 | <mml:mfenced open="(" close=")"> | |
143 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
144 | <mml:mi mathvariant="italic">c</mml:mi> | |
145 | </mml:msub> | |
146 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
147 | <mml:mi mathvariant="italic">c</mml:mi> | |
148 | </mml:msub> | |
149 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
150 | <mml:mi mathvariant="italic">c</mml:mi> | |
151 | </mml:msub> | |
152 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
153 | <mml:mi mathvariant="italic">c</mml:mi> | |
154 | </mml:msub> | |
155 | </mml:mfenced> | |
156 | </mml:math></inlineequation>. | |
157 | They are understood to have integer values between 0 and | |
158 | <inlineequation><mml:math> | |
159 | <!-- eqn: ( k sub R , k sub G , k sub B , k sub A ):--> | |
160 | <mml:mfenced open="(" close=")"> | |
161 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
162 | <mml:mi mathvariant="italic">R</mml:mi> | |
163 | </mml:msub> | |
164 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
165 | <mml:mi mathvariant="italic">G</mml:mi> | |
166 | </mml:msub> | |
167 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
168 | <mml:mi mathvariant="italic">B</mml:mi> | |
169 | </mml:msub> | |
170 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
171 | <mml:mi mathvariant="italic">A</mml:mi> | |
172 | </mml:msub> | |
173 | </mml:mfenced> | |
174 | </mml:math></inlineequation>, | |
175 | where | |
176 | </para> | |
177 | <para> | |
178 | <para> | |
179 | <inlineequation><mml:math> | |
180 | <!-- eqn: k sub c = 2 sup {m sub c} - 1:--> | |
181 | <mml:mrow> | |
182 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
183 | <mml:mi mathvariant="italic">c</mml:mi> | |
184 | </mml:msub> | |
185 | <mml:mo>=</mml:mo> | |
186 | <mml:mrow> | |
187 | <mml:msup><mml:mn>2</mml:mn> | |
188 | <mml:mfenced open="" close=""> | |
189 | <mml:msub><mml:mi mathvariant="italic">m</mml:mi> | |
190 | <mml:mi mathvariant="italic">c</mml:mi> | |
191 | </mml:msub> | |
192 | </mml:mfenced> | |
193 | </mml:msup> | |
194 | <mml:mo>-</mml:mo> | |
195 | <mml:mn>1</mml:mn> | |
196 | </mml:mrow> | |
197 | </mml:mrow> | |
198 | </mml:math></inlineequation> | |
199 | </para> | |
200 | </para> | |
201 | <para> | |
202 | and | |
203 | <inlineequation><mml:math> | |
204 | <!-- eqn: ( m sub R , m sub G , m sub B , m sub A ):--> | |
205 | <mml:mfenced open="(" close=")"> | |
206 | <mml:msub><mml:mi mathvariant="italic">m</mml:mi> | |
207 | <mml:mi mathvariant="italic">R</mml:mi> | |
208 | </mml:msub> | |
209 | <mml:msub><mml:mi mathvariant="italic">m</mml:mi> | |
210 | <mml:mi mathvariant="italic">G</mml:mi> | |
211 | </mml:msub> | |
212 | <mml:msub><mml:mi mathvariant="italic">m</mml:mi> | |
213 | <mml:mi mathvariant="italic">B</mml:mi> | |
214 | </mml:msub> | |
215 | <mml:msub><mml:mi mathvariant="italic">m</mml:mi> | |
216 | <mml:mi mathvariant="italic">A</mml:mi> | |
217 | </mml:msub> | |
218 | </mml:mfenced> | |
219 | </mml:math></inlineequation> | |
220 | is the number of red, | |
221 | green, | |
222 | blue, | |
223 | and alpha bitplanes. | |
224 | </para> | |
225 | <para> | |
226 | Source and destination scale factors are referred to as | |
227 | <inlineequation><mml:math> | |
228 | <!-- eqn: ( s sub R , s sub G , s sub B , s sub A ):--> | |
229 | <mml:mfenced open="(" close=")"> | |
230 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
231 | <mml:mi mathvariant="italic">R</mml:mi> | |
232 | </mml:msub> | |
233 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
234 | <mml:mi mathvariant="italic">G</mml:mi> | |
235 | </mml:msub> | |
236 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
237 | <mml:mi mathvariant="italic">B</mml:mi> | |
238 | </mml:msub> | |
239 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
240 | <mml:mi mathvariant="italic">A</mml:mi> | |
241 | </mml:msub> | |
242 | </mml:mfenced> | |
243 | </mml:math></inlineequation> | |
244 | and | |
245 | <inlineequation><mml:math> | |
246 | <!-- eqn: ( d sub R , d sub G , d sub B , d sub A ):--> | |
247 | <mml:mfenced open="(" close=")"> | |
248 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
249 | <mml:mi mathvariant="italic">R</mml:mi> | |
250 | </mml:msub> | |
251 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
252 | <mml:mi mathvariant="italic">G</mml:mi> | |
253 | </mml:msub> | |
254 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
255 | <mml:mi mathvariant="italic">B</mml:mi> | |
256 | </mml:msub> | |
257 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
258 | <mml:mi mathvariant="italic">A</mml:mi> | |
259 | </mml:msub> | |
260 | </mml:mfenced> | |
261 | </mml:math></inlineequation>. | |
262 | The scale factors described in the table, | |
263 | denoted | |
264 | <inlineequation><mml:math> | |
265 | <!-- eqn: ( f sub R , f sub G , f sub B , f sub A ):--> | |
266 | <mml:mfenced open="(" close=")"> | |
267 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
268 | <mml:mi mathvariant="italic">R</mml:mi> | |
269 | </mml:msub> | |
270 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
271 | <mml:mi mathvariant="italic">G</mml:mi> | |
272 | </mml:msub> | |
273 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
274 | <mml:mi mathvariant="italic">B</mml:mi> | |
275 | </mml:msub> | |
276 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
277 | <mml:mi mathvariant="italic">A</mml:mi> | |
278 | </mml:msub> | |
279 | </mml:mfenced> | |
280 | </mml:math></inlineequation>, | |
281 | represent either source or destination factors. | |
282 | All scale factors have range | |
283 | <inlineequation><mml:math> | |
284 | <!-- eqn: [0,1]:--> | |
285 | <mml:mfenced open="[" close="]"> | |
286 | <mml:mn>0</mml:mn> | |
287 | <mml:mn>1</mml:mn> | |
288 | </mml:mfenced> | |
289 | </mml:math></inlineequation>. | |
290 | </para> | |
291 | <para> | |
292 | </para> | |
293 | <informaltable frame="topbot"> | |
294 | <tgroup cols="2" align="left"> | |
295 | <colspec/> | |
296 | <colspec/> | |
297 | <thead> | |
298 | <row> | |
299 | <entry rowsep="1" align="left"><emphasis role="bold"> | |
300 | Parameter | |
301 | </emphasis></entry> | |
302 | <entry rowsep="1" align="left"><emphasis role="bold"> | |
303 | <inlineequation><mml:math> | |
304 | <!-- eqn: ( f sub R , f sub G , f sub B , f sub A ):--> | |
305 | <mml:mfenced open="(" close=")"> | |
306 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
307 | <mml:mi mathvariant="italic">R</mml:mi> | |
308 | </mml:msub> | |
309 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
310 | <mml:mi mathvariant="italic">G</mml:mi> | |
311 | </mml:msub> | |
312 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
313 | <mml:mi mathvariant="italic">B</mml:mi> | |
314 | </mml:msub> | |
315 | <mml:msub><mml:mi mathvariant="italic">f</mml:mi> | |
316 | <mml:mi mathvariant="italic">A</mml:mi> | |
317 | </mml:msub> | |
318 | </mml:mfenced> | |
319 | </mml:math></inlineequation> | |
320 | </emphasis></entry> | |
321 | </row> | |
322 | </thead> | |
323 | <tbody> | |
324 | <row> | |
325 | <entry align="left"> | |
326 | <constant>GL_ZERO</constant> | |
327 | </entry> | |
328 | <entry align="left"> | |
329 | <inlineequation><mml:math> | |
330 | <!-- eqn: ( 0, 0, 0, 0 ):--> | |
331 | <mml:mfenced open="(" close=")"> | |
332 | <mml:mn>0</mml:mn> | |
333 | <mml:mn>0</mml:mn> | |
334 | <mml:mn>0</mml:mn> | |
335 | <mml:mn>0</mml:mn> | |
336 | </mml:mfenced> | |
337 | </mml:math></inlineequation> | |
338 | </entry> | |
339 | </row> | |
340 | <row> | |
341 | <entry align="left"> | |
342 | <constant>GL_ONE</constant> | |
343 | </entry> | |
344 | <entry align="left"> | |
345 | <inlineequation><mml:math> | |
346 | <!-- eqn: ( 1, 1, 1, 1 ):--> | |
347 | <mml:mfenced open="(" close=")"> | |
348 | <mml:mn>1</mml:mn> | |
349 | <mml:mn>1</mml:mn> | |
350 | <mml:mn>1</mml:mn> | |
351 | <mml:mn>1</mml:mn> | |
352 | </mml:mfenced> | |
353 | </mml:math></inlineequation> | |
354 | </entry> | |
355 | </row> | |
356 | <row> | |
357 | <entry align="left"> | |
358 | <constant>GL_SRC_COLOR</constant> | |
359 | </entry> | |
360 | <entry align="left"> | |
361 | <inlineequation><mml:math> | |
362 | <!-- eqn: ( R sub s / k sub R , G sub s / k sub G , B sub s / k sub B , A sub s / k sub A ):--> | |
363 | <mml:mfenced open="(" close=")"> | |
364 | <mml:mfrac> | |
365 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
366 | <mml:mi mathvariant="italic">s</mml:mi> | |
367 | </mml:msub> | |
368 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
369 | <mml:mi mathvariant="italic">R</mml:mi> | |
370 | </mml:msub> | |
371 | </mml:mfrac> | |
372 | <mml:mfrac> | |
373 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
374 | <mml:mi mathvariant="italic">s</mml:mi> | |
375 | </mml:msub> | |
376 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
377 | <mml:mi mathvariant="italic">G</mml:mi> | |
378 | </mml:msub> | |
379 | </mml:mfrac> | |
380 | <mml:mfrac> | |
381 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
382 | <mml:mi mathvariant="italic">s</mml:mi> | |
383 | </mml:msub> | |
384 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
385 | <mml:mi mathvariant="italic">B</mml:mi> | |
386 | </mml:msub> | |
387 | </mml:mfrac> | |
388 | <mml:mfrac> | |
389 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
390 | <mml:mi mathvariant="italic">s</mml:mi> | |
391 | </mml:msub> | |
392 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
393 | <mml:mi mathvariant="italic">A</mml:mi> | |
394 | </mml:msub> | |
395 | </mml:mfrac> | |
396 | </mml:mfenced> | |
397 | </mml:math></inlineequation> | |
398 | </entry> | |
399 | </row> | |
400 | <row> | |
401 | <entry align="left"> | |
402 | <constant>GL_ONE_MINUS_SRC_COLOR</constant> | |
403 | </entry> | |
404 | <entry align="left"> | |
405 | <inlineequation><mml:math> | |
406 | <!-- eqn: ( 1, 1, 1, 1 ) - (R sub s / k sub R , G sub s / k sub G , B sub s / k sub B , A sub s / k sub A ):--> | |
407 | <mml:mrow> | |
408 | <mml:mfenced open="(" close=")"> | |
409 | <mml:mn>1</mml:mn> | |
410 | <mml:mn>1</mml:mn> | |
411 | <mml:mn>1</mml:mn> | |
412 | <mml:mn>1</mml:mn> | |
413 | </mml:mfenced> | |
414 | <mml:mo>-</mml:mo> | |
415 | <mml:mfenced open="(" close=")"> | |
416 | <mml:mfrac> | |
417 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
418 | <mml:mi mathvariant="italic">s</mml:mi> | |
419 | </mml:msub> | |
420 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
421 | <mml:mi mathvariant="italic">R</mml:mi> | |
422 | </mml:msub> | |
423 | </mml:mfrac> | |
424 | <mml:mfrac> | |
425 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
426 | <mml:mi mathvariant="italic">s</mml:mi> | |
427 | </mml:msub> | |
428 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
429 | <mml:mi mathvariant="italic">G</mml:mi> | |
430 | </mml:msub> | |
431 | </mml:mfrac> | |
432 | <mml:mfrac> | |
433 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
434 | <mml:mi mathvariant="italic">s</mml:mi> | |
435 | </mml:msub> | |
436 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
437 | <mml:mi mathvariant="italic">B</mml:mi> | |
438 | </mml:msub> | |
439 | </mml:mfrac> | |
440 | <mml:mfrac> | |
441 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
442 | <mml:mi mathvariant="italic">s</mml:mi> | |
443 | </mml:msub> | |
444 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
445 | <mml:mi mathvariant="italic">A</mml:mi> | |
446 | </mml:msub> | |
447 | </mml:mfrac> | |
448 | </mml:mfenced> | |
449 | </mml:mrow> | |
450 | </mml:math></inlineequation> | |
451 | </entry> | |
452 | </row> | |
453 | <row> | |
454 | <entry align="left"> | |
455 | <constant>GL_DST_COLOR</constant> | |
456 | </entry> | |
457 | <entry align="left"> | |
458 | <inlineequation><mml:math> | |
459 | <!-- eqn: ( R sub d / k sub R , G sub d / k sub G , B sub d / k sub B , A sub d / k sub A ):--> | |
460 | <mml:mfenced open="(" close=")"> | |
461 | <mml:mfrac> | |
462 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
463 | <mml:mi mathvariant="italic">d</mml:mi> | |
464 | </mml:msub> | |
465 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
466 | <mml:mi mathvariant="italic">R</mml:mi> | |
467 | </mml:msub> | |
468 | </mml:mfrac> | |
469 | <mml:mfrac> | |
470 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
471 | <mml:mi mathvariant="italic">d</mml:mi> | |
472 | </mml:msub> | |
473 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
474 | <mml:mi mathvariant="italic">G</mml:mi> | |
475 | </mml:msub> | |
476 | </mml:mfrac> | |
477 | <mml:mfrac> | |
478 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
479 | <mml:mi mathvariant="italic">d</mml:mi> | |
480 | </mml:msub> | |
481 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
482 | <mml:mi mathvariant="italic">B</mml:mi> | |
483 | </mml:msub> | |
484 | </mml:mfrac> | |
485 | <mml:mfrac> | |
486 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
487 | <mml:mi mathvariant="italic">d</mml:mi> | |
488 | </mml:msub> | |
489 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
490 | <mml:mi mathvariant="italic">A</mml:mi> | |
491 | </mml:msub> | |
492 | </mml:mfrac> | |
493 | </mml:mfenced> | |
494 | </mml:math></inlineequation> | |
495 | </entry> | |
496 | </row> | |
497 | <row> | |
498 | <entry align="left"> | |
499 | <constant>GL_ONE_MINUS_DST_COLOR</constant> | |
500 | </entry> | |
501 | <entry align="left"> | |
502 | <inlineequation><mml:math> | |
503 | <!-- eqn: ( 1, 1, 1, 1 ) - (R sub d / k sub R , G sub d / k sub G , B sub d / k sub B , A sub d / k sub A ):--> | |
504 | <mml:mrow> | |
505 | <mml:mfenced open="(" close=")"> | |
506 | <mml:mn>1</mml:mn> | |
507 | <mml:mn>1</mml:mn> | |
508 | <mml:mn>1</mml:mn> | |
509 | <mml:mn>1</mml:mn> | |
510 | </mml:mfenced> | |
511 | <mml:mo>-</mml:mo> | |
512 | <mml:mfenced open="(" close=")"> | |
513 | <mml:mfrac> | |
514 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
515 | <mml:mi mathvariant="italic">d</mml:mi> | |
516 | </mml:msub> | |
517 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
518 | <mml:mi mathvariant="italic">R</mml:mi> | |
519 | </mml:msub> | |
520 | </mml:mfrac> | |
521 | <mml:mfrac> | |
522 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
523 | <mml:mi mathvariant="italic">d</mml:mi> | |
524 | </mml:msub> | |
525 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
526 | <mml:mi mathvariant="italic">G</mml:mi> | |
527 | </mml:msub> | |
528 | </mml:mfrac> | |
529 | <mml:mfrac> | |
530 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
531 | <mml:mi mathvariant="italic">d</mml:mi> | |
532 | </mml:msub> | |
533 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
534 | <mml:mi mathvariant="italic">B</mml:mi> | |
535 | </mml:msub> | |
536 | </mml:mfrac> | |
537 | <mml:mfrac> | |
538 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
539 | <mml:mi mathvariant="italic">d</mml:mi> | |
540 | </mml:msub> | |
541 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
542 | <mml:mi mathvariant="italic">A</mml:mi> | |
543 | </mml:msub> | |
544 | </mml:mfrac> | |
545 | </mml:mfenced> | |
546 | </mml:mrow> | |
547 | </mml:math></inlineequation> | |
548 | </entry> | |
549 | </row> | |
550 | <row> | |
551 | <entry align="left"> | |
552 | <constant>GL_SRC_ALPHA</constant> | |
553 | </entry> | |
554 | <entry align="left"> | |
555 | <inlineequation><mml:math> | |
556 | <!-- eqn: ( A sub s / k sub A , A sub s / k sub A , A sub s / k sub A , A sub s / k sub A ):--> | |
557 | <mml:mfenced open="(" close=")"> | |
558 | <mml:mfrac> | |
559 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
560 | <mml:mi mathvariant="italic">s</mml:mi> | |
561 | </mml:msub> | |
562 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
563 | <mml:mi mathvariant="italic">A</mml:mi> | |
564 | </mml:msub> | |
565 | </mml:mfrac> | |
566 | <mml:mfrac> | |
567 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
568 | <mml:mi mathvariant="italic">s</mml:mi> | |
569 | </mml:msub> | |
570 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
571 | <mml:mi mathvariant="italic">A</mml:mi> | |
572 | </mml:msub> | |
573 | </mml:mfrac> | |
574 | <mml:mfrac> | |
575 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
576 | <mml:mi mathvariant="italic">s</mml:mi> | |
577 | </mml:msub> | |
578 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
579 | <mml:mi mathvariant="italic">A</mml:mi> | |
580 | </mml:msub> | |
581 | </mml:mfrac> | |
582 | <mml:mfrac> | |
583 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
584 | <mml:mi mathvariant="italic">s</mml:mi> | |
585 | </mml:msub> | |
586 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
587 | <mml:mi mathvariant="italic">A</mml:mi> | |
588 | </mml:msub> | |
589 | </mml:mfrac> | |
590 | </mml:mfenced> | |
591 | </mml:math></inlineequation> | |
592 | </entry> | |
593 | </row> | |
594 | <row> | |
595 | <entry align="left"> | |
596 | <constant>GL_ONE_MINUS_SRC_ALPHA</constant> | |
597 | </entry> | |
598 | <entry align="left"> | |
599 | <inlineequation><mml:math> | |
600 | <!-- eqn: ( 1, 1, 1, 1 ) - (A sub s / k sub A , A sub s / k sub A , A sub s / k sub A , A sub s / k sub A ):--> | |
601 | <mml:mrow> | |
602 | <mml:mfenced open="(" close=")"> | |
603 | <mml:mn>1</mml:mn> | |
604 | <mml:mn>1</mml:mn> | |
605 | <mml:mn>1</mml:mn> | |
606 | <mml:mn>1</mml:mn> | |
607 | </mml:mfenced> | |
608 | <mml:mo>-</mml:mo> | |
609 | <mml:mfenced open="(" close=")"> | |
610 | <mml:mfrac> | |
611 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
612 | <mml:mi mathvariant="italic">s</mml:mi> | |
613 | </mml:msub> | |
614 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
615 | <mml:mi mathvariant="italic">A</mml:mi> | |
616 | </mml:msub> | |
617 | </mml:mfrac> | |
618 | <mml:mfrac> | |
619 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
620 | <mml:mi mathvariant="italic">s</mml:mi> | |
621 | </mml:msub> | |
622 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
623 | <mml:mi mathvariant="italic">A</mml:mi> | |
624 | </mml:msub> | |
625 | </mml:mfrac> | |
626 | <mml:mfrac> | |
627 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
628 | <mml:mi mathvariant="italic">s</mml:mi> | |
629 | </mml:msub> | |
630 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
631 | <mml:mi mathvariant="italic">A</mml:mi> | |
632 | </mml:msub> | |
633 | </mml:mfrac> | |
634 | <mml:mfrac> | |
635 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
636 | <mml:mi mathvariant="italic">s</mml:mi> | |
637 | </mml:msub> | |
638 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
639 | <mml:mi mathvariant="italic">A</mml:mi> | |
640 | </mml:msub> | |
641 | </mml:mfrac> | |
642 | </mml:mfenced> | |
643 | </mml:mrow> | |
644 | </mml:math></inlineequation> | |
645 | </entry> | |
646 | </row> | |
647 | <row> | |
648 | <entry align="left"> | |
649 | <constant>GL_DST_ALPHA</constant> | |
650 | </entry> | |
651 | <entry align="left"> | |
652 | <inlineequation><mml:math> | |
653 | <!-- eqn: ( A sub d / k sub A , A sub d / k sub A , A sub d / k sub A , A sub d / k sub A ):--> | |
654 | <mml:mfenced open="(" close=")"> | |
655 | <mml:mfrac> | |
656 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
657 | <mml:mi mathvariant="italic">d</mml:mi> | |
658 | </mml:msub> | |
659 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
660 | <mml:mi mathvariant="italic">A</mml:mi> | |
661 | </mml:msub> | |
662 | </mml:mfrac> | |
663 | <mml:mfrac> | |
664 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
665 | <mml:mi mathvariant="italic">d</mml:mi> | |
666 | </mml:msub> | |
667 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
668 | <mml:mi mathvariant="italic">A</mml:mi> | |
669 | </mml:msub> | |
670 | </mml:mfrac> | |
671 | <mml:mfrac> | |
672 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
673 | <mml:mi mathvariant="italic">d</mml:mi> | |
674 | </mml:msub> | |
675 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
676 | <mml:mi mathvariant="italic">A</mml:mi> | |
677 | </mml:msub> | |
678 | </mml:mfrac> | |
679 | <mml:mfrac> | |
680 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
681 | <mml:mi mathvariant="italic">d</mml:mi> | |
682 | </mml:msub> | |
683 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
684 | <mml:mi mathvariant="italic">A</mml:mi> | |
685 | </mml:msub> | |
686 | </mml:mfrac> | |
687 | </mml:mfenced> | |
688 | </mml:math></inlineequation> | |
689 | </entry> | |
690 | </row> | |
691 | <row> | |
692 | <entry align="left"> | |
693 | <constant>GL_ONE_MINUS_DST_ALPHA</constant> | |
694 | </entry> | |
695 | <entry align="left"> | |
696 | <inlineequation><mml:math> | |
697 | <!-- eqn: ( 1, 1, 1, 1 ) - ( A sub d / k sub A , A sub d / k sub A , A sub d / k sub A , A sub d / k sub A ):--> | |
698 | <mml:mrow> | |
699 | <mml:mfenced open="(" close=")"> | |
700 | <mml:mn>1</mml:mn> | |
701 | <mml:mn>1</mml:mn> | |
702 | <mml:mn>1</mml:mn> | |
703 | <mml:mn>1</mml:mn> | |
704 | </mml:mfenced> | |
705 | <mml:mo>-</mml:mo> | |
706 | <mml:mfenced open="(" close=")"> | |
707 | <mml:mfrac> | |
708 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
709 | <mml:mi mathvariant="italic">d</mml:mi> | |
710 | </mml:msub> | |
711 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
712 | <mml:mi mathvariant="italic">A</mml:mi> | |
713 | </mml:msub> | |
714 | </mml:mfrac> | |
715 | <mml:mfrac> | |
716 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
717 | <mml:mi mathvariant="italic">d</mml:mi> | |
718 | </mml:msub> | |
719 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
720 | <mml:mi mathvariant="italic">A</mml:mi> | |
721 | </mml:msub> | |
722 | </mml:mfrac> | |
723 | <mml:mfrac> | |
724 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
725 | <mml:mi mathvariant="italic">d</mml:mi> | |
726 | </mml:msub> | |
727 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
728 | <mml:mi mathvariant="italic">A</mml:mi> | |
729 | </mml:msub> | |
730 | </mml:mfrac> | |
731 | <mml:mfrac> | |
732 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
733 | <mml:mi mathvariant="italic">d</mml:mi> | |
734 | </mml:msub> | |
735 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
736 | <mml:mi mathvariant="italic">A</mml:mi> | |
737 | </mml:msub> | |
738 | </mml:mfrac> | |
739 | </mml:mfenced> | |
740 | </mml:mrow> | |
741 | </mml:math></inlineequation> | |
742 | </entry> | |
743 | </row> | |
744 | <row> | |
745 | <entry align="left"> | |
746 | <constant>GL_CONSTANT_COLOR</constant> | |
747 | </entry> | |
748 | <entry align="left"> | |
749 | <inlineequation><mml:math> | |
750 | <!-- eqn: ( R sub c, G sub c, B sub c, A sub c ):--> | |
751 | <mml:mfenced open="(" close=")"> | |
752 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
753 | <mml:mi mathvariant="italic">c</mml:mi> | |
754 | </mml:msub> | |
755 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
756 | <mml:mi mathvariant="italic">c</mml:mi> | |
757 | </mml:msub> | |
758 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
759 | <mml:mi mathvariant="italic">c</mml:mi> | |
760 | </mml:msub> | |
761 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
762 | <mml:mi mathvariant="italic">c</mml:mi> | |
763 | </mml:msub> | |
764 | </mml:mfenced> | |
765 | </mml:math></inlineequation> | |
766 | </entry> | |
767 | </row> | |
768 | <row> | |
769 | <entry align="left"> | |
770 | <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant> | |
771 | </entry> | |
772 | <entry align="left"> | |
773 | <inlineequation><mml:math> | |
774 | <!-- eqn: ( 1, 1, 1, 1 ) - ( R sub c, G sub c, B sub c, A sub c ):--> | |
775 | <mml:mrow> | |
776 | <mml:mfenced open="(" close=")"> | |
777 | <mml:mn>1</mml:mn> | |
778 | <mml:mn>1</mml:mn> | |
779 | <mml:mn>1</mml:mn> | |
780 | <mml:mn>1</mml:mn> | |
781 | </mml:mfenced> | |
782 | <mml:mo>-</mml:mo> | |
783 | <mml:mfenced open="(" close=")"> | |
784 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
785 | <mml:mi mathvariant="italic">c</mml:mi> | |
786 | </mml:msub> | |
787 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
788 | <mml:mi mathvariant="italic">c</mml:mi> | |
789 | </mml:msub> | |
790 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
791 | <mml:mi mathvariant="italic">c</mml:mi> | |
792 | </mml:msub> | |
793 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
794 | <mml:mi mathvariant="italic">c</mml:mi> | |
795 | </mml:msub> | |
796 | </mml:mfenced> | |
797 | </mml:mrow> | |
798 | </mml:math></inlineequation> | |
799 | </entry> | |
800 | </row> | |
801 | <row> | |
802 | <entry align="left"> | |
803 | <constant>GL_CONSTANT_ALPHA</constant> | |
804 | </entry> | |
805 | <entry align="left"> | |
806 | <inlineequation><mml:math> | |
807 | <!-- eqn: ( A sub c, A sub c, A sub c, A sub c ):--> | |
808 | <mml:mfenced open="(" close=")"> | |
809 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
810 | <mml:mi mathvariant="italic">c</mml:mi> | |
811 | </mml:msub> | |
812 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
813 | <mml:mi mathvariant="italic">c</mml:mi> | |
814 | </mml:msub> | |
815 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
816 | <mml:mi mathvariant="italic">c</mml:mi> | |
817 | </mml:msub> | |
818 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
819 | <mml:mi mathvariant="italic">c</mml:mi> | |
820 | </mml:msub> | |
821 | </mml:mfenced> | |
822 | </mml:math></inlineequation> | |
823 | </entry> | |
824 | </row> | |
825 | <row> | |
826 | <entry align="left"> | |
827 | <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant> | |
828 | </entry> | |
829 | <entry align="left"> | |
830 | <inlineequation><mml:math> | |
831 | <!-- eqn: ( 1, 1, 1, 1 ) - ( A sub c, A sub c, A sub c, A sub c ):--> | |
832 | <mml:mrow> | |
833 | <mml:mfenced open="(" close=")"> | |
834 | <mml:mn>1</mml:mn> | |
835 | <mml:mn>1</mml:mn> | |
836 | <mml:mn>1</mml:mn> | |
837 | <mml:mn>1</mml:mn> | |
838 | </mml:mfenced> | |
839 | <mml:mo>-</mml:mo> | |
840 | <mml:mfenced open="(" close=")"> | |
841 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
842 | <mml:mi mathvariant="italic">c</mml:mi> | |
843 | </mml:msub> | |
844 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
845 | <mml:mi mathvariant="italic">c</mml:mi> | |
846 | </mml:msub> | |
847 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
848 | <mml:mi mathvariant="italic">c</mml:mi> | |
849 | </mml:msub> | |
850 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
851 | <mml:mi mathvariant="italic">c</mml:mi> | |
852 | </mml:msub> | |
853 | </mml:mfenced> | |
854 | </mml:mrow> | |
855 | </mml:math></inlineequation> | |
856 | </entry> | |
857 | </row> | |
858 | <row> | |
859 | <entry align="left"> | |
860 | <constant>GL_SRC_ALPHA_SATURATE</constant> | |
861 | </entry> | |
862 | <entry align="left"> | |
863 | <inlineequation><mml:math> | |
864 | <!-- eqn: ( i, i, i, 1 ):--> | |
865 | <mml:mfenced open="(" close=")"> | |
866 | <mml:mi mathvariant="italic">i</mml:mi> | |
867 | <mml:mi mathvariant="italic">i</mml:mi> | |
868 | <mml:mi mathvariant="italic">i</mml:mi> | |
869 | <mml:mn>1</mml:mn> | |
870 | </mml:mfenced> | |
871 | </mml:math></inlineequation> | |
872 | </entry> | |
873 | </row> | |
874 | </tbody> | |
875 | </tgroup> | |
876 | </informaltable> | |
877 | <para> | |
878 | In the table, | |
879 | </para> | |
880 | <para> | |
881 | <para> | |
882 | <inlineequation><mml:math> | |
883 | <!-- eqn: i = min (A sub s , k sub A - A sub d ) / k sub A:--> | |
884 | <mml:mrow> | |
885 | <mml:mi mathvariant="italic">i</mml:mi> | |
886 | <mml:mo>=</mml:mo> | |
887 | <mml:mfrac> | |
888 | <mml:mrow> | |
889 | <mml:mi mathvariant="italic">min</mml:mi> | |
890 | <mml:mo>⁡</mml:mo> | |
891 | <mml:mfenced open="(" close=")"> | |
892 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
893 | <mml:mi mathvariant="italic">s</mml:mi> | |
894 | </mml:msub> | |
895 | <mml:mrow> | |
896 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
897 | <mml:mi mathvariant="italic">A</mml:mi> | |
898 | </mml:msub> | |
899 | <mml:mo>-</mml:mo> | |
900 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
901 | <mml:mi mathvariant="italic">d</mml:mi> | |
902 | </mml:msub> | |
903 | </mml:mrow> | |
904 | </mml:mfenced> | |
905 | </mml:mrow> | |
906 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
907 | <mml:mi mathvariant="italic">A</mml:mi> | |
908 | </mml:msub> | |
909 | </mml:mfrac> | |
910 | </mml:mrow> | |
911 | </mml:math></inlineequation> | |
912 | </para> | |
913 | </para> | |
914 | <para> | |
915 | To determine the blended RGBA values of a pixel when drawing in RGBA mode, | |
916 | the system uses the following equations: | |
917 | </para> | |
918 | <para> | |
919 | <para> | |
920 | <inlineequation><mml:math> | |
921 | <!-- eqn: R sub d = min ( k sub R, R sub s s sub R + R sub d d sub R ):--> | |
922 | <mml:mrow> | |
923 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
924 | <mml:mi mathvariant="italic">d</mml:mi> | |
925 | </mml:msub> | |
926 | <mml:mo>=</mml:mo> | |
927 | <mml:mrow> | |
928 | <mml:mi mathvariant="italic">min</mml:mi> | |
929 | <mml:mo>⁡</mml:mo> | |
930 | <mml:mfenced open="(" close=")"> | |
931 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
932 | <mml:mi mathvariant="italic">R</mml:mi> | |
933 | </mml:msub> | |
934 | <mml:mrow> | |
935 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
936 | <mml:mi mathvariant="italic">s</mml:mi> | |
937 | </mml:msub> | |
938 | <mml:mo>⁢</mml:mo> | |
939 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
940 | <mml:mi mathvariant="italic">R</mml:mi> | |
941 | </mml:msub> | |
942 | <mml:mo>+</mml:mo> | |
943 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
944 | <mml:mi mathvariant="italic">d</mml:mi> | |
945 | </mml:msub> | |
946 | <mml:mo>⁢</mml:mo> | |
947 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
948 | <mml:mi mathvariant="italic">R</mml:mi> | |
949 | </mml:msub> | |
950 | </mml:mrow> | |
951 | </mml:mfenced> | |
952 | </mml:mrow> | |
953 | </mml:mrow> | |
954 | </mml:math></inlineequation> | |
955 | <inlineequation><mml:math> | |
956 | <!-- eqn: G sub d = min ( k sub G, G sub s s sub G + G sub d d sub G ):--> | |
957 | <mml:mrow> | |
958 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
959 | <mml:mi mathvariant="italic">d</mml:mi> | |
960 | </mml:msub> | |
961 | <mml:mo>=</mml:mo> | |
962 | <mml:mrow> | |
963 | <mml:mi mathvariant="italic">min</mml:mi> | |
964 | <mml:mo>⁡</mml:mo> | |
965 | <mml:mfenced open="(" close=")"> | |
966 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
967 | <mml:mi mathvariant="italic">G</mml:mi> | |
968 | </mml:msub> | |
969 | <mml:mrow> | |
970 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
971 | <mml:mi mathvariant="italic">s</mml:mi> | |
972 | </mml:msub> | |
973 | <mml:mo>⁢</mml:mo> | |
974 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
975 | <mml:mi mathvariant="italic">G</mml:mi> | |
976 | </mml:msub> | |
977 | <mml:mo>+</mml:mo> | |
978 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
979 | <mml:mi mathvariant="italic">d</mml:mi> | |
980 | </mml:msub> | |
981 | <mml:mo>⁢</mml:mo> | |
982 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
983 | <mml:mi mathvariant="italic">G</mml:mi> | |
984 | </mml:msub> | |
985 | </mml:mrow> | |
986 | </mml:mfenced> | |
987 | </mml:mrow> | |
988 | </mml:mrow> | |
989 | </mml:math></inlineequation> | |
990 | <inlineequation><mml:math> | |
991 | <!-- eqn: B sub d = min ( k sub B, B sub s s sub B + B sub d d sub B ):--> | |
992 | <mml:mrow> | |
993 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
994 | <mml:mi mathvariant="italic">d</mml:mi> | |
995 | </mml:msub> | |
996 | <mml:mo>=</mml:mo> | |
997 | <mml:mrow> | |
998 | <mml:mi mathvariant="italic">min</mml:mi> | |
999 | <mml:mo>⁡</mml:mo> | |
1000 | <mml:mfenced open="(" close=")"> | |
1001 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
1002 | <mml:mi mathvariant="italic">B</mml:mi> | |
1003 | </mml:msub> | |
1004 | <mml:mrow> | |
1005 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
1006 | <mml:mi mathvariant="italic">s</mml:mi> | |
1007 | </mml:msub> | |
1008 | <mml:mo>⁢</mml:mo> | |
1009 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
1010 | <mml:mi mathvariant="italic">B</mml:mi> | |
1011 | </mml:msub> | |
1012 | <mml:mo>+</mml:mo> | |
1013 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
1014 | <mml:mi mathvariant="italic">d</mml:mi> | |
1015 | </mml:msub> | |
1016 | <mml:mo>⁢</mml:mo> | |
1017 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
1018 | <mml:mi mathvariant="italic">B</mml:mi> | |
1019 | </mml:msub> | |
1020 | </mml:mrow> | |
1021 | </mml:mfenced> | |
1022 | </mml:mrow> | |
1023 | </mml:mrow> | |
1024 | </mml:math></inlineequation> | |
1025 | <inlineequation><mml:math> | |
1026 | <!-- eqn: A sub d = min ( k sub A, A sub s s sub A + A sub d d sub A ):--> | |
1027 | <mml:mrow> | |
1028 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
1029 | <mml:mi mathvariant="italic">d</mml:mi> | |
1030 | </mml:msub> | |
1031 | <mml:mo>=</mml:mo> | |
1032 | <mml:mrow> | |
1033 | <mml:mi mathvariant="italic">min</mml:mi> | |
1034 | <mml:mo>⁡</mml:mo> | |
1035 | <mml:mfenced open="(" close=")"> | |
1036 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
1037 | <mml:mi mathvariant="italic">A</mml:mi> | |
1038 | </mml:msub> | |
1039 | <mml:mrow> | |
1040 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
1041 | <mml:mi mathvariant="italic">s</mml:mi> | |
1042 | </mml:msub> | |
1043 | <mml:mo>⁢</mml:mo> | |
1044 | <mml:msub><mml:mi mathvariant="italic">s</mml:mi> | |
1045 | <mml:mi mathvariant="italic">A</mml:mi> | |
1046 | </mml:msub> | |
1047 | <mml:mo>+</mml:mo> | |
1048 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
1049 | <mml:mi mathvariant="italic">d</mml:mi> | |
1050 | </mml:msub> | |
1051 | <mml:mo>⁢</mml:mo> | |
1052 | <mml:msub><mml:mi mathvariant="italic">d</mml:mi> | |
1053 | <mml:mi mathvariant="italic">A</mml:mi> | |
1054 | </mml:msub> | |
1055 | </mml:mrow> | |
1056 | </mml:mfenced> | |
1057 | </mml:mrow> | |
1058 | </mml:mrow> | |
1059 | </mml:math></inlineequation> | |
1060 | </para> | |
1061 | </para> | |
1062 | <para> | |
1063 | Despite the apparent precision of the above equations, | |
1064 | blending arithmetic is not exactly specified, | |
1065 | because blending operates with imprecise integer color values. | |
1066 | However, | |
1067 | a blend factor that should be equal to 1 | |
1068 | is guaranteed not to modify its multiplicand, | |
1069 | and a blend factor equal to 0 reduces its multiplicand to 0. | |
1070 | For example, | |
1071 | when <parameter>sfactor</parameter> is <constant>GL_SRC_ALPHA</constant>, | |
1072 | <parameter>dfactor</parameter> is <constant>GL_ONE_MINUS_SRC_ALPHA</constant>, | |
1073 | and | |
1074 | <inlineequation><mml:math> | |
1075 | <!-- eqn: A sub s:--> | |
1076 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
1077 | <mml:mi mathvariant="italic">s</mml:mi> | |
1078 | </mml:msub> | |
1079 | </mml:math></inlineequation> | |
1080 | is equal to | |
1081 | <inlineequation><mml:math> | |
1082 | <!-- eqn: k sub A:--> | |
1083 | <mml:msub><mml:mi mathvariant="italic">k</mml:mi> | |
1084 | <mml:mi mathvariant="italic">A</mml:mi> | |
1085 | </mml:msub> | |
1086 | </mml:math></inlineequation>, | |
1087 | the equations reduce to simple replacement: | |
1088 | </para> | |
1089 | <para> | |
1090 | <para> | |
1091 | <inlineequation><mml:math> | |
1092 | <!-- eqn: R sub d = R sub s:--> | |
1093 | <mml:mrow> | |
1094 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
1095 | <mml:mi mathvariant="italic">d</mml:mi> | |
1096 | </mml:msub> | |
1097 | <mml:mo>=</mml:mo> | |
1098 | <mml:msub><mml:mi mathvariant="italic">R</mml:mi> | |
1099 | <mml:mi mathvariant="italic">s</mml:mi> | |
1100 | </mml:msub> | |
1101 | </mml:mrow> | |
1102 | </mml:math></inlineequation> | |
1103 | <inlineequation><mml:math> | |
1104 | <!-- eqn: G sub d = G sub s:--> | |
1105 | <mml:mrow> | |
1106 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
1107 | <mml:mi mathvariant="italic">d</mml:mi> | |
1108 | </mml:msub> | |
1109 | <mml:mo>=</mml:mo> | |
1110 | <mml:msub><mml:mi mathvariant="italic">G</mml:mi> | |
1111 | <mml:mi mathvariant="italic">s</mml:mi> | |
1112 | </mml:msub> | |
1113 | </mml:mrow> | |
1114 | </mml:math></inlineequation> | |
1115 | <inlineequation><mml:math> | |
1116 | <!-- eqn: B sub d = B sub s:--> | |
1117 | <mml:mrow> | |
1118 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
1119 | <mml:mi mathvariant="italic">d</mml:mi> | |
1120 | </mml:msub> | |
1121 | <mml:mo>=</mml:mo> | |
1122 | <mml:msub><mml:mi mathvariant="italic">B</mml:mi> | |
1123 | <mml:mi mathvariant="italic">s</mml:mi> | |
1124 | </mml:msub> | |
1125 | </mml:mrow> | |
1126 | </mml:math></inlineequation> | |
1127 | <inlineequation><mml:math> | |
1128 | <!-- eqn: A sub d = A sub s:--> | |
1129 | <mml:mrow> | |
1130 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
1131 | <mml:mi mathvariant="italic">d</mml:mi> | |
1132 | </mml:msub> | |
1133 | <mml:mo>=</mml:mo> | |
1134 | <mml:msub><mml:mi mathvariant="italic">A</mml:mi> | |
1135 | <mml:mi mathvariant="italic">s</mml:mi> | |
1136 | </mml:msub> | |
1137 | </mml:mrow> | |
1138 | </mml:math></inlineequation> | |
1139 | </para> | |
1140 | </para> | |
1141 | <para> | |
1142 | </para> | |
1143 | </refsect1> | |
1144 | <refsect1 id="examples"><title>Examples</title> | |
1145 | <para> | |
1146 | </para> | |
1147 | <para> | |
1148 | Transparency is best implemented using blend function | |
1149 | (<constant>GL_SRC_ALPHA</constant>, <constant>GL_ONE_MINUS_SRC_ALPHA</constant>) | |
1150 | with primitives sorted from farthest to nearest. | |
1151 | Note that this transparency calculation does not require | |
1152 | the presence of alpha bitplanes in the frame buffer. | |
1153 | </para> | |
1154 | <para> | |
1155 | Blend function | |
1156 | (<constant>GL_SRC_ALPHA</constant>, <constant>GL_ONE_MINUS_SRC_ALPHA</constant>) | |
1157 | is also useful for rendering antialiased points and lines | |
1158 | in arbitrary order. | |
1159 | </para> | |
1160 | <para> | |
1161 | Polygon antialiasing is optimized using blend function | |
1162 | (<constant>GL_SRC_ALPHA_SATURATE</constant>, <constant>GL_ONE</constant>) | |
1163 | with polygons sorted from nearest to farthest. | |
1164 | (See the <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> reference page and the | |
1165 | <constant>GL_POLYGON_SMOOTH</constant> argument for information on polygon antialiasing.) | |
1166 | Destination alpha bitplanes, | |
1167 | which must be present for this blend function to operate correctly, | |
1168 | store the accumulated coverage. | |
1169 | </para> | |
1170 | </refsect1> | |
1171 | <refsect1 id="notes"><title>Notes</title> | |
1172 | <para> | |
1173 | Incoming (source) alpha is correctly thought of as a material opacity, | |
1174 | ranging from 1.0 | |
1175 | (<inlineequation><mml:math> | |
1176 | <!-- eqn: K sub A:--> | |
1177 | <mml:msub><mml:mi mathvariant="italic">K</mml:mi> | |
1178 | <mml:mi mathvariant="italic">A</mml:mi> | |
1179 | </mml:msub> | |
1180 | </mml:math></inlineequation>), | |
1181 | representing complete opacity, | |
1182 | to 0.0 (0), representing complete | |
1183 | transparency. | |
1184 | </para> | |
1185 | <para> | |
1186 | When more than one color buffer is enabled for drawing, | |
1187 | the GL performs blending separately for each enabled buffer, | |
1188 | using the contents of that buffer for destination color. | |
1189 | (See <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>.) | |
1190 | </para> | |
1191 | <para> | |
1192 | Blending affects only RGBA rendering. | |
1193 | It is ignored by color index renderers. | |
1194 | </para> | |
1195 | <para> | |
1196 | <constant>GL_CONSTANT_COLOR</constant>, <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>, | |
1197 | <constant>GL_CONSTANT_ALPHA</constant>, <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant> are available only | |
1198 | if the GL version is 1.4 or greater or if the <code>ARB_imaging</code> is | |
1199 | supported by your implementation. | |
1200 | </para> | |
1201 | <para> | |
1202 | <constant>GL_SRC_COLOR</constant> and <constant>GL_ONE_MINUS_SRC_COLOR</constant> are valid only for | |
1203 | <parameter>sfactor</parameter> if the GL version is 1.4 or greater. | |
1204 | </para> | |
1205 | <para> | |
1206 | <constant>GL_DST_COLOR</constant> and <constant>GL_ONE_MINUS_DST_COLOR</constant> are valid only for | |
1207 | <parameter>dfactor</parameter> if the GL version is 1.4 or greater. | |
1208 | </para> | |
1209 | </refsect1> | |
1210 | <refsect1 id="errors"><title>Errors</title> | |
1211 | <para> | |
1212 | <constant>GL_INVALID_ENUM</constant> is generated if either <parameter>sfactor</parameter> or <parameter>dfactor</parameter> is not an | |
1213 | accepted value. | |
1214 | </para> | |
1215 | <para> | |
1216 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBlendFunc</function> | |
1217 | is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> | |
1218 | and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>. | |
1219 | </para> | |
1220 | </refsect1> | |
1221 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
1222 | <para> | |
1223 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_BLEND_SRC</constant> | |
1224 | </para> | |
1225 | <para> | |
1226 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_BLEND_DST</constant> | |
1227 | </para> | |
1228 | <para> | |
1229 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_BLEND</constant> | |
1230 | </para> | |
1231 | <para> | |
1232 | </para> | |
1233 | </refsect1> | |
1234 | <refsect1 id="seealso"><title>See Also</title> | |
1235 | <para> | |
1236 | <citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>, | |
1237 | <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry>, | |
1238 | <citerefentry><refentrytitle>glBlendEquation</refentrytitle></citerefentry>, | |
1239 | <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>, | |
1240 | <citerefentry><refentrytitle>glClear</refentrytitle></citerefentry>, | |
1241 | <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>, | |
1242 | <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, | |
1243 | <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>, | |
1244 | <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry> | |
1245 | ||
1246 | </para> | |
1247 | </refsect1> | |
1248 | <refsect1 id="Copyright"><title>Copyright</title> | |
1249 | <para> | |
1250 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
1251 | Silicon Graphics, Inc. This document is licensed under the SGI | |
1252 | Free Software B License. For details, see | |
1253 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
1254 | </para> | |
1255 | </refsect1> | |
1256 | </refentry> |