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<span id="Rectangles"></span><div class="header">
<p>
Next: <a href="Grid.html" accesskey="n" rel="next">Grid</a>, Previous: <a href="Vectors.html" accesskey="p" rel="prev">Vectors</a>, Up: <a href="Math.html" accesskey="u" rel="up">Math</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="Rectangles-1"></span><h4 class="subsection">2.2.3 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
“hitboxes” in platformers or using them for the “broad phase” 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>
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