1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 2017-2021 David Thompson davet@gnu.org
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled "GNU
Free Documentation License".
A copy of the license is also available from the Free Software
Foundation Web site at http://www.gnu.org/licenses/fdl.html.
* Chickadee: (chickadee). Game programming toolkit for Guile.
The document was typeset with
http://www.texinfo.org/ (GNU Texinfo).
-->
<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Render Settings (The Chickadee Game Toolkit)</title>
<meta name="description" content="Render Settings (The Chickadee Game Toolkit)">
<meta name="keywords" content="Render Settings (The Chickadee Game Toolkit)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<link href="index.html" rel="start" title="Top">
<link href="Index.html" rel="index" title="Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Graphics.html" rel="up" title="Graphics">
<link href="Rendering-Engine.html" rel="next" title="Rendering Engine">
<link href="Viewports.html" rel="prev" title="Viewports">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
@media (min-width: 1140px) {
body {
margin-left: 14rem;
margin-right: 4rem;
max-width: 52rem;
}
}
@media (min-width: 800px) and (max-width: 1140px) {
body {
margin-left: 6rem;
margin-right: 4rem;
max-width: 52rem;
}
}
@media (max-width: 800px) {
body {
margin: 1rem;
}
}
-->
</style>
<link rel="stylesheet" type="text/css" href="https://dthompson.us/css/dthompson.css">
</head>
<body lang="en">
<span id="Render-Settings"></span><div class="header">
<p>
Next: <a href="Rendering-Engine.html" accesskey="n" rel="next">Rendering Engine</a>, Previous: <a href="Viewports.html" accesskey="p" rel="prev">Viewports</a>, Up: <a href="Graphics.html" accesskey="u" rel="up">Graphics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<span id="Render-Settings-1"></span><h4 class="subsection">5.3.16 Render Settings</h4>
<span id="Blending"></span><h4 class="subsubsection">5.3.16.1 Blending</h4>
<p>Rendering a scene often involves drawing layers of objects that
overlap each other. Blending determines how two overlapping pixels
are combined in the final image that is rendered to the screen. The
<code>(chickadee graphics blend)</code> module provides a data type for
blending modes.
</p>
<p>Chickadee provides the following blend modes:
</p>
<dl>
<dt id="index-blend_003aalpha">Variable: <strong>blend:alpha</strong></dt>
<dd><p>Blend pixels according to the values of their alpha channels. This is
the most commonly used blend mode.
</p></dd></dl>
<dl>
<dt id="index-blend_003areplace">Variable: <strong>blend:replace</strong></dt>
<dd><p>Overwrite the output pixel color with the color being drawn.
</p></dd></dl>
<dl>
<dt id="index-blend_003aadd">Variable: <strong>blend:add</strong></dt>
<dd><p>Add all pixel color values together. The more colors blended
together, the more white the final color becomes.
</p></dd></dl>
<dl>
<dt id="index-blend_003asubtract">Variable: <strong>blend:subtract</strong></dt>
<dd><p>Subtract all pixel color values. The more colors blended together,
the more black the final color becomes.
</p></dd></dl>
<dl>
<dt id="index-blend_003amultiply">Variable: <strong>blend:multiply</strong></dt>
</dl>
<dl>
<dt id="index-blend_003adarken">Variable: <strong>blend:darken</strong></dt>
</dl>
<dl>
<dt id="index-blend_003alighten">Variable: <strong>blend:lighten</strong></dt>
</dl>
<dl>
<dt id="index-blend_003ascreen">Variable: <strong>blend:screen</strong></dt>
</dl>
<p>Custom blend modes can be created using the <code>make-blend-mode</code> procedure:
</p>
<dl>
<dt id="index-make_002dblend_002dmode">Procedure: <strong>make-blend-mode</strong> <em>equation source-function destination-function</em></dt>
<dd><p>Return a new custom blend mode that applies <var>source-function</var> to
the source color, <var>destination-function</var> to the destination color,
and finally applies <var>equation</var> to the transformed
source/destination color values. These arguments are <em>not</em>
procedures, but symbolic representations of the functions that OpenGL
supports.
</p>
<p>Valid values for <var>equation</var> are:
</p>
<ul>
<li> <code>add</code>
</li><li> <code>subtract</code>
</li><li> <code>reverse-subtract</code>
</li><li> <code>min</code>
</li><li> <code>max</code>
</li><li> <code>alpha-min</code>
</li><li> <code>alpha-max</code>
</li></ul>
<p>Valid values for <var>source-function</var> are:
</p>
<ul>
<li> <code>zero</code>
</li><li> <code>one</code>
</li><li> <code>destination-color</code>
</li><li> <code>one-minus-destination-color</code>
</li><li> <code>source-alpha-saturate</code>
</li><li> <code>source-alpha</code>
</li><li> <code>one-minus-source-alpha</code>
</li><li> <code>destination-alpha</code>
</li><li> <code>one-minus-destination-alpha</code>
</li><li> <code>constant-color</code>
</li><li> <code>one-minus-constant-color</code>
</li><li> <code>constant-alpha</code>
</li><li> <code>one-minus-constant-alpha</code>
</li></ul>
<p>Valid values for <var>destination-function</var> are:
</p>
<ul>
<li> <code>zero</code>
</li><li> <code>one</code>
</li><li> <code>source-color</code>
</li><li> <code>one-minus-source-color</code>
</li><li> <code>source-alpha</code>
</li><li> <code>one-minus-source-alpha</code>
</li><li> <code>destination-alpha</code>
</li><li> <code>one-minus-destination-alpha</code>
</li><li> <code>constant-color</code>
</li><li> <code>one-minus-constant-color</code>
</li><li> <code>constant-alpha</code>
</li><li> <code>one-minus-constant-alpha</code>
</li></ul>
</dd></dl>
<span id="Polygon-Modes-and-Culling"></span><h4 class="subsubsection">5.3.16.2 Polygon Modes and Culling</h4>
<p>The <code>(chickadee graphics polygon)</code> module provides access to the
<code>g:polygon-mode</code> and <code>g:cull-face-mode</code> render states.
</p>
<dl>
<dt id="index-fill_002dpolygon_002dmode">Variable: <strong>fill-polygon-mode</strong></dt>
<dd><p>Completely fill in the polygon. This is the default mode.
</p></dd></dl>
<dl>
<dt id="index-line_002dpolygon_002dmode">Variable: <strong>line-polygon-mode</strong></dt>
<dd><p>Render only the edges of the polygon. Produces a wireframe.
</p></dd></dl>
<dl>
<dt id="index-point_002dpolygon_002dmode">Variable: <strong>point-polygon-mode</strong></dt>
<dd><p>Render only the vertex positions as points.
</p></dd></dl>
<dl>
<dt id="index-make_002dpolygon_002dmode">Procedure: <strong>make-polygon-mode</strong> <em>front back</em></dt>
<dd><p>Return a new polygon mode that uses the method <var>front</var> for the
front face and <var>back</var> for the back face. The valid modes are
<code>fill</code>, <code>line</code>, and <var>point</var>.
</p></dd></dl>
<dl>
<dt id="index-polygon_002dmode_003f">Procedure: <strong>polygon-mode?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a polygon mode.
</p></dd></dl>
<dl>
<dt id="index-current_002dpolygon_002dmode">Procedure: <strong>current-polygon-mode</strong></dt>
<dd><p>Return the current polygon mode.
</p></dd></dl>
<dl>
<dt id="index-g_003apolygon_002dmode">Variable: <strong>g:polygon-mode</strong></dt>
<dd><p>Render state for polygon modes (see <a href="Rendering-Engine.html">Rendering Engine</a>.)
</p></dd></dl>
<dl>
<dt id="index-no_002dcull_002dface_002dmode">Variable: <strong>no-cull-face-mode</strong></dt>
<dd><p>Don’t cull any faces.
</p></dd></dl>
<dl>
<dt id="index-back_002dcull_002dface_002dmode">Variable: <strong>back-cull-face-mode</strong></dt>
<dd><p>Cull only back faces.
</p></dd></dl>
<dl>
<dt id="index-front_002dcull_002dface_002dmode">Variable: <strong>front-cull-face-mode</strong></dt>
<dd><p>Cull only front faces.
</p></dd></dl>
<dl>
<dt id="index-front_002dand_002dback_002dcull_002dface_002dmode">Variable: <strong>front-and-back-cull-face-mode</strong></dt>
<dd><p>Cull both front and back faces.
</p></dd></dl>
<dl>
<dt id="index-cull_002dface_002dmode_003f">Procedure: <strong>cull-face-mode?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a cull face mode.
</p></dd></dl>
<dl>
<dt id="index-cull_002dface_002dmode_002dfront_003f">Procedure: <strong>cull-face-mode-front?</strong> <em>cull-face-mode</em></dt>
<dd><p>Return <code>#t</code> if <var>cull-face-mode</var> culls front faces.
</p></dd></dl>
<dl>
<dt id="index-cull_002dface_002dmode_002dback_003f">Procedure: <strong>cull-face-mode-back?</strong> <em>cull-face-mode</em></dt>
<dd><p>Return <code>#t</code> if <var>cull-face-mode</var> culls back faces.
</p></dd></dl>
<dl>
<dt id="index-current_002dcull_002dface_002dmode">Procedure: <strong>current-cull-face-mode</strong></dt>
<dd><p>Return the current cull face mode.
</p></dd></dl>
<dl>
<dt id="index-g_003acull_002dface_002dmode">Variable: <strong>g:cull-face-mode</strong></dt>
<dd><p>Render state for cull face modes (see <a href="Rendering-Engine.html">Rendering Engine</a>.)
</p></dd></dl>
<span id="Depth-Testing"></span><h4 class="subsubsection">5.3.16.3 Depth Testing</h4>
<p>The <code>(chickadee graphics depth)</code> module provides access to the
<code>g:depth-test</code> render state.
</p>
<dl>
<dt id="index-make_002ddepth_002dtest">Procedure: <strong>make-depth-test</strong> <em>[#:write? #t] [#:function 'less-than] [#:near 0.0] [#:far 1.0]</em></dt>
<dd>
<p>Return a new depth test object. If <var>write</var> is <code>#t</code>, the
depth buffer will be written to during a draw call. <var>near</var> and
<var>far</var> define the min/max Z values for which depth testing may
pass.
</p>
<p><var>function</var> specifies how the depth value of pixel being drawn
compares to the depth value that is already in the depth buffer. When
this comparison is true, the depth test passes and the pixel is drawn.
When it fails, the pixel is discarded.
</p>
<p>The possible values of <var>function</var> are:
</p>
<ul>
<li> <code>always</code>
</li><li> <code>never</code>
</li><li> <code>equal</code>
</li><li> <code>not-equal</code>
</li><li> <code>less-than</code>
</li><li> <code>less-than-or-equal</code>
</li><li> <code>greater-than</code>
</li><li> <code>greater-than-or-equal</code>
</li></ul>
</dd></dl>
<dl>
<dt id="index-depth_002dtest_003f">Procedure: <strong>depth-test?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> when <var>obj</var> is a depth test object.
</p></dd></dl>
<dl>
<dt id="index-depth_002dtest_002dwrite_003f">Procedure: <strong>depth-test-write?</strong> <em>depth-test</em></dt>
<dd><p>Return <code>#t</code> when <var>depth-test</var> will write to the depth buffer.
</p></dd></dl>
<dl>
<dt id="index-depth_002dtest_002dfunction">Procedure: <strong>depth-test-function</strong> <em>depth-test</em></dt>
<dd><p>Return the comparison function of <var>depth-test</var>.
</p></dd></dl>
<dl>
<dt id="index-depth_002dtest_002dnear">Procedure: <strong>depth-test-near</strong> <em>depth-test</em></dt>
<dd><p>Return the near Z value of <var>depth-test</var>.
</p></dd></dl>
<dl>
<dt id="index-depth_002dtest_002dfar">Procedure: <strong>depth-test-far</strong> <em>depth-test</em></dt>
<dd><p>Return the far Z value of <var>depth-test</var>.
</p></dd></dl>
<dl>
<dt id="index-current_002ddepth_002dtest">Procedure: <strong>current-depth-test</strong></dt>
<dd><p>Return the current depth test.
</p></dd></dl>
<dl>
<dt id="index-g_003adepth_002dtest">Variable: <strong>g:depth-test</strong></dt>
<dd><p>Render state for depth tests (see <a href="Rendering-Engine.html">Rendering Engine</a>.)
</p></dd></dl>
<span id="Stencil-Testing"></span><h4 class="subsubsection">5.3.16.4 Stencil Testing</h4>
<p>The <code>(chickadee graphics stencil)</code> module provides access to the
<code>g:stencil-test</code> render state.
</p>
<dl>
<dt id="index-default_002dstencil_002dtest">Variable: <strong>default-stencil-test</strong></dt>
<dd><p>A stencil test that always passes.
</p></dd></dl>
<dl>
<dt id="index-make_002dstencil_002dtest">Procedure: <strong>make-stencil-test</strong> <em>[#:mask #xFF] [#:function always] [#:function-mask #xFF] [#:reference 0] [#:on-fail keep] [#:on-depth-fail keep] [#:on-pass keep] [#:mask-front mask] [#:mask-back mask] [#:function-mask-front function-mask] [#:function-mask-back function-mask] [#:refrence-front reference] [#:reference-back reference] [#:on-fail-front on-fail] [#:on-fail-back on-fail] [#:on-depth-fail-front on-depth-fail] [#:on-depth-fail-back on-depth-fail] [#:on-pass-front on-pass] [#:on-pass-back on-pass]</em></dt>
<dd>
<p>Return a new stencil test object. Different configurations can be
used for the front and back faces by using the arguments that end in
“front” or “back”.
</p>
<p>Valid values for <var>on-pass</var>, <var>on-fail</var>, and <var>on-depth-fail</var>
are:
</p>
<ul>
<li> <code>zero</code>
</li><li> <code>keep</code>
</li><li> <code>replace</code>
</li><li> <code>increment</code>
</li><li> <code>increment-wrap</code>
</li><li> <code>decrement</code>
</li><li> <code>decrement-wrap</code>
</li><li> <code>invert</code>
</li></ul>
<p>Valid values for <var>function</var> are:
</p>
<ul>
<li> <code>always</code>
</li><li> <code>never</code>
</li><li> <code>equal</code>
</li><li> <code>not-equal</code>
</li><li> <code>less-than</code>
</li><li> <code>less-than-or-equal</code>
</li><li> <code>greater-than</code>
</li><li> <code>greater-than-or-equal</code>
</li></ul>
</dd></dl>
<dl>
<dt id="index-stencil_002dtest_003f">Procedure: <strong>stencil-test?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> when <var>obj</var> is a stencil test object.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dmask_002dfront">Procedure: <strong>stencil-test-mask-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front mask of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dmask_002dback">Procedure: <strong>stencil-test-mask-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back mask of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dfunction_002dfront">Procedure: <strong>stencil-test-function-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front function of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dfunction_002dback">Procedure: <strong>stencil-test-function-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back function of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dfunction_002dmask_002dfront">Procedure: <strong>stencil-test-function-mask-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front function-mask of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dfunction_002dmask_002dback">Procedure: <strong>stencil-test-function-mask-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back function-mask of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dreference_002dfront">Procedure: <strong>stencil-test-reference-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front reference value of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002dreference_002dback">Procedure: <strong>stencil-test-reference-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back reference value of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002don_002dfail_002dfront">Procedure: <strong>stencil-test-on-fail-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front failure action of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002don_002dfail_002dback">Procedure: <strong>stencil-test-on-fail-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back failure action of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002don_002ddepth_002dfail_002dfront">Procedure: <strong>stencil-test-on-depth-fail-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front depth test failure action of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002don_002ddepth_002dfail_002dback">Procedure: <strong>stencil-test-on-depth-fail-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back depth test failure action of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002don_002dpass_002dfront">Procedure: <strong>stencil-test-on-pass-front</strong> <em>stencil-test</em></dt>
<dd><p>Return the front pass action of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-stencil_002dtest_002don_002dpass_002dback">Procedure: <strong>stencil-test-on-pass-back</strong> <em>stencil-test</em></dt>
<dd><p>Return the back pass action of <var>stencil-test</var>.
</p></dd></dl>
<dl>
<dt id="index-current_002dstencil_002dtest">Procedure: <strong>current-stencil-test</strong></dt>
<dd><p>Return the current stencil test.
</p></dd></dl>
<dl>
<dt id="index-g_003astencil_002dtest">Variable: <strong>g:stencil-test</strong></dt>
<dd><p>Render state for stencil testing (see <a href="Rendering-Engine.html">Rendering Engine</a>.)
</p></dd></dl>
<span id="Multisample-Antialiasing"></span><h4 class="subsubsection">5.3.16.5 Multisample Antialiasing</h4>
<p>Multisample antialiasing is a feature supported by many, but not all,
graphics cards. It is a nice easy way to improve the final frame that
the user sees, particularly in 3D scenes. The <code>(chickadee
graphics multisample)</code> module provides access to the
<code>g:multisample?</code> render state.
</p>
<dl>
<dt id="index-current_002dmultisample">Procedure: <strong>current-multisample</strong></dt>
<dd><p>Return <code>#t</code> if multisampling is enabled.
</p></dd></dl>
<dl>
<dt id="index-g_003amultisample_003f">Variable: <strong>g:multisample?</strong></dt>
<dd><p>Render state for multisampling (see <a href="Rendering-Engine.html">Rendering Engine</a>.)
</p></dd></dl>
<hr>
<div class="header">
<p>
Next: <a href="Rendering-Engine.html" accesskey="n" rel="next">Rendering Engine</a>, Previous: <a href="Viewports.html" accesskey="p" rel="prev">Viewports</a>, Up: <a href="Graphics.html" accesskey="u" rel="up">Graphics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
