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<span id="Quaternions-1"></span><h4 class="subsection">2.2.6 Quaternions</h4>
<p>In game development, the quaternion is most often used to represent
rotations. Why not use a matrix for that, you may ask. Unlike
matrices, quaternions can be interpolated (animated) and produce a
meaningful result. When interpolating two quaternions, there is a
smooth transition from one rotation to another, whereas interpolating
two matrices would yield garbage.
</p>
<dl>
<dt id="index-quaternion">Procedure: <strong>quaternion</strong> <em>x y z w</em></dt>
<dd><p>Return a new quaternion with values <var>x</var>, <var>y</var>, <var>z</var>, and
<var>w</var>.
</p></dd></dl>
<dl>
<dt id="index-quaternion_003f">Procedure: <strong>quaternion?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a quaternion.
</p></dd></dl>
<dl>
<dt id="index-quaternion_002dw">Procedure: <strong>quaternion-w</strong> <em>q</em></dt>
<dd><p>Return the W component of the quaternion <var>q</var>.
</p></dd></dl>
<dl>
<dt id="index-quaternion_002dx">Procedure: <strong>quaternion-x</strong> <em>q</em></dt>
<dd><p>Return the X component of the quaternion <var>q</var>.
</p></dd></dl>
<dl>
<dt id="index-quaternion_002dy">Procedure: <strong>quaternion-y</strong> <em>q</em></dt>
<dd><p>Return the Y component of the quaternion <var>q</var>.
</p></dd></dl>
<dl>
<dt id="index-quaternion_002dz">Procedure: <strong>quaternion-z</strong> <em>q</em></dt>
<dd><p>Return the Z component of the quaternion <var>q</var>.
</p></dd></dl>
<dl>
<dt id="index-make_002didentity_002dquaternion">Procedure: <strong>make-identity-quaternion</strong></dt>
<dd><p>Return the identity quaternion.
</p></dd></dl>
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