summaryrefslogtreecommitdiff
path: root/manuals/chickadee/Rectangles.html
blob: 487fac732fd8a0177c631799ca1eca41c8032604 (plain)
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
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!--  Copyright (C) 2017-2023  David Thompson dthompson2@worcester.edu

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>Rectangles (The Chickadee Game Toolkit)</title>

<meta name="description" content="Rectangles (The Chickadee Game Toolkit)" />
<meta name="keywords" content="Rectangles (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="Math.html" rel="up" title="Math" />
<link href="Matrices.html" rel="next" title="Matrices" />
<link href="Vectors.html" rel="prev" title="Vectors" />
<style type="text/css">
&lt;!--
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;
    }
}

--&gt;
</style>
<link rel="stylesheet" type="text/css" href="https://dthompson.us/css/dthompson.css" />


</head>

<body lang="en">
<span id="Rectangles"></span><div class="header">
<p>
Next: <a href="Matrices.html" accesskey="n" rel="next">Matrices</a>, Previous: <a href="Vectors.html" accesskey="p" rel="prev">Vectors</a>, Up: <a href="Math.html" accesskey="u" rel="up">Math</a> &nbsp; [<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="Rectangles-1"></span><h4 class="subsection">5.2.3 Rectangles</h4>

<p>The <code>(chickadee math rect)</code> module provides an API for
manipulating axis-aligned bounding boxes (AABBs).  AABBs are often
used for collision detection in games.  Common use-cases are defining
&ldquo;hitboxes&rdquo; in platformers or using them for the &ldquo;broad phase&rdquo; of a
collision detection algorithm that uses a more complex (and thus
slower) method of determining the actual collisions.
</p>
<p>Like some of the other math modules, there exists a collection of
functions that do in-place modification of rectangles for use in
performance critical code paths.
</p>
<dl>
<dt id="index-rect">Procedure: <strong>rect</strong> <em>x y width height</em></dt>
<dt id="index-make_002drect">Procedure: <strong>make-rect</strong> <em><var>x</var> <var>y</var> <var>width</var> <var>height</var></em></dt>
<dd><p>Create a new rectangle that is <var>width</var> by <var>height</var> in size and
whose bottom-left corner is located at (<var>x</var>, <var>y</var>).
</p></dd></dl>

<dl>
<dt id="index-rect_003f">Procedure: <strong>rect?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a rectangle.
</p></dd></dl>

<dl>
<dt id="index-rect_002dwithin_003f">Procedure: <strong>rect-within?</strong> <em>rect1 rect2</em></dt>
<dd><p>Return <code>#t</code> if <var>rect2</var> is completely within <var>rect1</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dintersects_003f">Procedure: <strong>rect-intersects?</strong> <em>rect1 rect2</em></dt>
<dd><p>Return <code>#t</code> if <var>rect2</var> overlaps <var>rect1</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dcontains_003f">Procedure: <strong>rect-contains?</strong> <em>rect x y</em></dt>
<dd><p>Return <code>#t</code> if the coordinates (<var>x</var>, <var>y</var>) are within
<var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dcontains_002dvec2_003f">Procedure: <strong>rect-contains-vec2?</strong> <em>rect v</em></dt>
<dd><p>Return <code>#t</code> if the 2D vector <var>v</var> is within the bounds of
<var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dx">Procedure: <strong>rect-x</strong> <em>rect</em></dt>
<dd><p>Return the X coordinate of the lower-left corner of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dy">Procedure: <strong>rect-y</strong> <em>rect</em></dt>
<dd><p>Return the Y coordinate of the lower-left corner of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dleft">Procedure: <strong>rect-left</strong> <em>rect</em></dt>
<dd><p>Return the left-most X coordinate of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dright">Procedure: <strong>rect-right</strong> <em>rect</em></dt>
<dd><p>Return the right-most X coordinate of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dbottom">Procedure: <strong>rect-bottom</strong> <em>rect</em></dt>
<dd><p>Return the bottom-most Y coordinate of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dtop">Procedure: <strong>rect-top</strong> <em>rect</em></dt>
<dd><p>Return the top-most Y coordinate of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dcenter_002dx">Procedure: <strong>rect-center-x</strong> <em>rect</em></dt>
<dd><p>Return the X coordinate of the center of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dcenter_002dy">Procedure: <strong>rect-center-y</strong> <em>rect</em></dt>
<dd><p>Return the Y coordinate of the center of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dwidth">Procedure: <strong>rect-width</strong> <em>rect</em></dt>
<dd><p>Return the width of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dheight">Procedure: <strong>rect-height</strong> <em>rect</em></dt>
<dd><p>Return the height of <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002darea">Procedure: <strong>rect-area</strong> <em>rect</em></dt>
<dd><p>Return the surface area covered by <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dclamp_002dx">Procedure: <strong>rect-clamp-x</strong> <em>rect x</em></dt>
<dd><p>Restrict <var>x</var> to the portion of the X axis covered by <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dclamp_002dy">Procedure: <strong>rect-clamp-y</strong> <em>rect y</em></dt>
<dd><p>Restrict <var>y</var> to the portion of the Y axis covered by <var>rect</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dclamp">Procedure: <strong>rect-clamp</strong> <em>rect1 rect2</em></dt>
<dd><p>Return a new rect that adjusts the location of <var>rect1</var> so that it
is completely within <var>rect2</var>.  An exception is thrown in the case
that <var>rect1</var> cannot fit completely within <var>rect2</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove">Procedure: <strong>rect-move</strong> <em>rect x y</em></dt>
<dd><p>Return a new rectangle based on <var>rect</var> but moved to the
coordinates (<var>x</var>, <var>y</var>).
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_002dvec2">Procedure: <strong>rect-move-vec2</strong> <em>rect v</em></dt>
<dd><p>Return a new rectangle based on <var>rect</var> but moved to the
coordinates in the 2D vector <var>v</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_002dby">Procedure: <strong>rect-move-by</strong> <em>rect x y</em></dt>
<dd><p>Return a new rectangle based on <var>rect</var> but moved by (<var>x</var>,
<var>y</var>) units relative to its current location.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_002dby_002dvec2">Procedure: <strong>rect-move-by-vec2</strong> <em>rect v</em></dt>
<dd><p>Return a new rectangle based on <var>rect</var> but moved by the 2D vector
<var>v</var> relative to its current location.
</p></dd></dl>

<dl>
<dt id="index-rect_002dinflate">Procedure: <strong>rect-inflate</strong> <em>rect width height</em></dt>
<dd><p>Return a new rectangle based on <var>rect</var>, but expanded by
<var>width</var> units on the X axis and <var>height</var> units on the Y axis,
while keeping the rectangle centered on the same point.
</p></dd></dl>

<dl>
<dt id="index-rect_002dunion">Procedure: <strong>rect-union</strong> <em>rect1 rect2</em></dt>
<dd><p>Return a new rectangle that completely covers the area of <var>rect1</var>
and <var>rect2</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dclip">Procedure: <strong>rect-clip</strong> <em>rect1 rect2</em></dt>
<dd><p>Return a new rectangle that is the overlapping region of <var>rect1</var>
and <var>rect2</var>.  If the two rectangles do not overlap, a rectangle of
0 width and 0 height is returned.
</p></dd></dl>

<dl>
<dt id="index-set_002drect_002dx_0021">Procedure: <strong>set-rect-x!</strong> <em>rect x</em></dt>
<dd><p>Set the left X coordinate of <var>rect</var> to <var>x</var>.
</p></dd></dl>

<dl>
<dt id="index-set_002drect_002dy_0021">Procedure: <strong>set-rect-y!</strong> <em>rect y</em></dt>
<dd><p>Set the bottom Y coordinate of <var>rect</var> to <var>y</var>.
</p></dd></dl>

<dl>
<dt id="index-set_002drect_002dwidth_0021">Procedure: <strong>set-rect-width!</strong> <em>rect width</em></dt>
<dd><p>Set the width of <var>rect</var> to <var>width</var>.
</p></dd></dl>

<dl>
<dt id="index-set_002drect_002dheight_0021">Procedure: <strong>set-rect-height!</strong> <em>rect height</em></dt>
<dd><p>Set the height of <var>rect</var> to <var>height</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_0021">Procedure: <strong>rect-move!</strong> <em>rect x y</em></dt>
<dd><p>Move <var>rect</var> to (<var>x</var>, <var>y</var>) in-place.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_002dvec2_0021">Procedure: <strong>rect-move-vec2!</strong> <em>rect v</em></dt>
<dd><p>Move <var>rect</var> to the 2D vector <var>v</var> in-place.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_002dby_0021">Procedure: <strong>rect-move-by!</strong> <em>rect x y</em></dt>
<dd><p>Move <var>rect</var> by (<var>x</var>, <var>y</var>) in-place.
</p></dd></dl>

<dl>
<dt id="index-rect_002dmove_002dby_002dvec2_0021">Procedure: <strong>rect-move-by-vec2!</strong> <em>rect v</em></dt>
<dd><p>Move <var>rect</var> by the 2D vector <var>v</var> in-place.
</p></dd></dl>

<dl>
<dt id="index-rect_002dinflate_0021">Procedure: <strong>rect-inflate!</strong> <em>rect width height</em></dt>
<dd><p>Expand <var>rect</var> by <var>width</var> and <var>height</var> in-place.
</p></dd></dl>

<dl>
<dt id="index-rect_002dunion_0021">Procedure: <strong>rect-union!</strong> <em>rect1 rect2</em></dt>
<dd><p>Modify <var>rect1</var> in-place to completely cover the area of both
<var>rect1</var> and <var>rect2</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dclip_0021">Procedure: <strong>rect-clip!</strong> <em>rect1 rect2</em></dt>
<dd><p>Modify <var>rect1</var> in-place to be the overlapping region of
<var>rect1</var> and <var>rect2</var>.
</p></dd></dl>

<dl>
<dt id="index-rect_002dclamp_0021">Procedure: <strong>rect-clamp!</strong> <em>rect1 rect2</em></dt>
<dd><p>Adjust the location of <var>rect1</var> in-place so that its bounds are
completely within <var>rect2</var>.  An exception is thrown in the case
that <var>rect1</var> cannot fit completely within <var>rect2</var>.
</p></dd></dl>

<dl>
<dt id="index-vec2_002dclamp_002dto_002drect_0021">Procedure: <strong>vec2-clamp-to-rect!</strong> <em>v rect</em></dt>
<dd><p>Restrict the coordinates of the 2D vector <var>v</var> so that they are
within the bounds of <var>rect</var>.  <var>v</var> is modified in-place.
</p></dd></dl>

<hr />
<div class="header">
<p>
Next: <a href="Matrices.html" accesskey="n" rel="next">Matrices</a>, Previous: <a href="Vectors.html" accesskey="p" rel="prev">Vectors</a>, Up: <a href="Math.html" accesskey="u" rel="up">Math</a> &nbsp; [<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>