doc/reference/cogl/html/cogl-Quaternions-(Rotations).html

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  24 <a href="#cogl-Quaternions-(Rotations).synopsis" class="shortcut">Top</a>
  25                    |
  26                   <a href="#cogl-Quaternions-(Rotations).description" class="shortcut">Description</a>
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  29 <div class="refentry">
  30 <a name="cogl-Quaternions-(Rotations)"></a><div class="titlepage"></div>
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  33 <h2><span class="refentrytitle"><a name="cogl-Quaternions-(Rotations).top_of_page"></a>Quaternions (Rotations)</span></h2>
  34 <p>Quaternions (Rotations) — Functions for initializing and manipulating
  35 quaternions.</p>
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  39 <div class="refsynopsisdiv">
  40 <a name="cogl-Quaternions-(Rotations).synopsis"></a><h2>Synopsis</h2>
  41 <pre class="synopsis">                    <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion">CoglQuaternion</a>;
  42 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init-identity" title="cogl_quaternion_init_identity ()">cogl_quaternion_init_identity</a>       (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);
  43 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init" title="cogl_quaternion_init ()">cogl_quaternion_init</a>                (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  44                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>,
  45                                                          <em class="parameter"><code><span class="type">float</span> x</code></em>,
  46                                                          <em class="parameter"><code><span class="type">float</span> y</code></em>,
  47                                                          <em class="parameter"><code><span class="type">float</span> z</code></em>);
  48 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init-from-angle-vector" title="cogl_quaternion_init_from_angle_vector ()">cogl_quaternion_init_from_angle_vector</a>
  49                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  50                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>,
  51                                                          <em class="parameter"><code>const <span class="type">float</span> *axis3f</code></em>);
  52 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init-from-array" title="cogl_quaternion_init_from_array ()">cogl_quaternion_init_from_array</a>     (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  53                                                          <em class="parameter"><code>const <span class="type">float</span> *array</code></em>);
  54 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init-from-x-rotation" title="cogl_quaternion_init_from_x_rotation ()">cogl_quaternion_init_from_x_rotation</a>
  55                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  56                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>);
  57 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init-from-y-rotation" title="cogl_quaternion_init_from_y_rotation ()">cogl_quaternion_init_from_y_rotation</a>
  58                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  59                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>);
  60 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-init-from-z-rotation" title="cogl_quaternion_init_from_z_rotation ()">cogl_quaternion_init_from_z_rotation</a>
  61                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  62                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>);
  63 <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-equal" title="cogl_quaternion_equal ()">cogl_quaternion_equal</a>               (<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gconstpointer"><span class="type">gconstpointer</span></a> v1</code></em>,
  64                                                          <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gconstpointer"><span class="type">gconstpointer</span></a> v2</code></em>);
  65 <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="returnvalue">CoglQuaternion</span></a> *    <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-copy" title="cogl_quaternion_copy ()">cogl_quaternion_copy</a>                (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *src</code></em>);
  66 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-free" title="cogl_quaternion_free ()">cogl_quaternion_free</a>                (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);
  67 <span class="returnvalue">float</span>               <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-get-rotation-angle" title="cogl_quaternion_get_rotation_angle ()">cogl_quaternion_get_rotation_angle</a>  (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);
  68 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-get-rotation-axis" title="cogl_quaternion_get_rotation_axis ()">cogl_quaternion_get_rotation_axis</a>   (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  69                                                          <em class="parameter"><code><span class="type">float</span> *vector3</code></em>);
  70 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-normalize" title="cogl_quaternion_normalize ()">cogl_quaternion_normalize</a>           (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);
  71 <span class="returnvalue">float</span>               <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-dot-product" title="cogl_quaternion_dot_product ()">cogl_quaternion_dot_product</a>         (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
  72                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>);
  73 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-invert" title="cogl_quaternion_invert ()">cogl_quaternion_invert</a>              (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);
  74 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-multiply" title="cogl_quaternion_multiply ()">cogl_quaternion_multiply</a>            (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
  75                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *left</code></em>,
  76                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *right</code></em>);
  77 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-pow" title="cogl_quaternion_pow ()">cogl_quaternion_pow</a>                 (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
  78                                                          <em class="parameter"><code><span class="type">float</span> exponent</code></em>);
  79 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-slerp" title="cogl_quaternion_slerp ()">cogl_quaternion_slerp</a>               (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
  80                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
  81                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>,
  82                                                          <em class="parameter"><code><span class="type">float</span> t</code></em>);
  83 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-nlerp" title="cogl_quaternion_nlerp ()">cogl_quaternion_nlerp</a>               (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
  84                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
  85                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>,
  86                                                          <em class="parameter"><code><span class="type">float</span> t</code></em>);
  87 <span class="returnvalue">void</span>                <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-squad" title="cogl_quaternion_squad ()">cogl_quaternion_squad</a>               (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
  88                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *prev</code></em>,
  89                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
  90                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>,
  91                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *next</code></em>,
  92                                                          <em class="parameter"><code><span class="type">float</span> t</code></em>);
  93 const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="returnvalue">CoglQuaternion</span></a> * <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-get-static-identity-quaternion" title="cogl_get_static_identity_quaternion ()">cogl_get_static_identity_quaternion</a>
  94                                                         (<em class="parameter"><code><span class="type">void</span></code></em>);
  95 const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="returnvalue">CoglQuaternion</span></a> * <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-get-static-zero-quaternion" title="cogl_get_static_zero_quaternion ()">cogl_get_static_zero_quaternion</a>  (<em class="parameter"><code><span class="type">void</span></code></em>);
  96 </pre>
  97 </div>
  98 <div class="refsect1">
  99 <a name="cogl-Quaternions-(Rotations).description"></a><h2>Description</h2>
 100 <p>
 101 Quaternions have become a standard form for representing 3D
 102 rotations and have some nice properties when compared with other
 103 representation such as (roll,pitch,yaw) Euler angles. They can be
 104 used to interpolate between different rotations and they don't
 105 suffer from a problem called "Gimbal lock" where two of the axis of
 106 rotation may become aligned and you loose a degree of freedom.
 107 (<a class="ulink" href="http://en.wikipedia.org/wiki/Gimbal_lock" target="_top">http://en.wikipedia.org/wiki/Gimbal_lock</a>).
 108 </p>
 109 </div>
 110 <div class="refsect1">
 111 <a name="cogl-Quaternions-(Rotations).details"></a><h2>Details</h2>
 112 <div class="refsect2">
 113 <a name="CoglQuaternion"></a><h3>CoglQuaternion</h3>
 114 <pre class="programlisting">typedef struct {
 115   float w;
 116
 117   float x;
 118   float y;
 119   float z;
 120
 121   float padding0;
 122   float padding1;
 123   float padding2;
 124   float padding3;
 125 } CoglQuaternion;
 126 </pre>
 127 <p>
 128 A quaternion is comprised of a scalar component and a 3D vector
 129 component. The scalar component is normally referred to as w and the
 130 vector might either be referred to as v or a (for axis) or expanded
 131 with the individual components: (x, y, z) A full quaternion would
 132 then be written as <span style="color: red">&lt;pre&gt;[w (x, y, z)]&lt;/pre&gt;</span>.
 133 </p>
 134 <p>
 135 Quaternions can be considered to represent an axis and angle
 136 pair although sadly these numbers are buried somewhat under some
 137 maths...
 138 </p>
 139 <p>
 140 For the curious you can see here that a given axis (a) and angle (𝜃)
 141 pair are represented in a quaternion as follows:
 142 </p>
 143 <div class="informalexample">
 144   <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 145     <tbody>
 146       <tr>
 147         <td class="listing_lines" align="right"><pre>1</pre></td>
 148         <td class="listing_code"><pre class="programlisting"><span class="symbol">[</span><span class="normal">w</span><span class="symbol">=</span><span class="function">cos</span><span class="symbol">(</span><span class="normal">𝜃</span><span class="symbol">/</span><span class="number">2</span><span class="symbol">)</span><span class="normal"> </span><span class="symbol">(</span><span class="normal"> x</span><span class="symbol">=</span><span class="function">sin</span><span class="symbol">(</span><span class="normal">𝜃</span><span class="symbol">/</span><span class="number">2</span><span class="symbol">)*</span><span class="normal">a</span><span class="symbol">.</span><span class="normal">x</span><span class="symbol">,</span><span class="normal"> y</span><span class="symbol">=</span><span class="function">sin</span><span class="symbol">(</span><span class="normal">𝜃</span><span class="symbol">/</span><span class="number">2</span><span class="symbol">)*</span><span class="normal">a</span><span class="symbol">.</span><span class="normal">y</span><span class="symbol">,</span><span class="normal"> z</span><span class="symbol">=</span><span class="function">sin</span><span class="symbol">(</span><span class="normal">𝜃</span><span class="symbol">/</span><span class="number">2</span><span class="symbol">)*</span><span class="normal">a</span><span class="symbol">.</span><span class="normal">x </span><span class="symbol">)]</span></pre></td>
 149       </tr>
 150     </tbody>
 151   </table>
 152 </div>
 153
 154 <p>
 155 </p>
 156 <p>
 157 Unit Quaternions:
 158 When using Quaternions to represent spatial orientations for 3D
 159 graphics it's always assumed you have a unit quaternion. The
 160 magnitude of a quaternion is defined as:
 161 </p>
 162 <div class="informalexample">
 163   <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 164     <tbody>
 165       <tr>
 166         <td class="listing_lines" align="right"><pre>1</pre></td>
 167         <td class="listing_code"><pre class="programlisting"><span class="function">sqrt</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">w² </span><span class="symbol">+</span><span class="normal"> x² </span><span class="symbol">+</span><span class="normal"> y² </span><span class="symbol">+</span><span class="normal"> z²</span><span class="symbol">)</span></pre></td>
 168       </tr>
 169     </tbody>
 170   </table>
 171 </div>
 172
 173 <p>
 174 and a unit quaternion satisfies this equation:
 175 </p>
 176 <div class="informalexample">
 177   <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 178     <tbody>
 179       <tr>
 180         <td class="listing_lines" align="right"><pre>1</pre></td>
 181         <td class="listing_code"><pre class="programlisting"><span class="normal">w² </span><span class="symbol">+</span><span class="normal"> x² </span><span class="symbol">+</span><span class="normal"> y² </span><span class="symbol">+</span><span class="normal"> z² </span><span class="symbol">=</span><span class="normal"> </span><span class="number">1</span></pre></td>
 182       </tr>
 183     </tbody>
 184   </table>
 185 </div>
 186
 187 <p>
 188 </p>
 189 <p>
 190 Thankfully most of the time we don't actually have to worry about
 191 the maths that goes on behind the scenes but if you are curious to
 192 learn more here are some external references:
 193 </p>
 194 <p>
 195 </p>
 196 <div class="itemizedlist"><ul class="itemizedlist" type="disc">
 197 <li class="listitem"><a class="ulink" href="http://mathworld.wolfram.com/Quaternion.html" target="_top">http://mathworld.wolfram.com/Quaternion.html</a></li>
 198 <li class="listitem"><a class="ulink" href="http://www.gamedev.net/reference/articles/article1095.asp" target="_top">http://www.gamedev.net/reference/articles/article1095.asp</a></li>
 199 <li class="listitem"><a class="ulink" href="http://www.cprogramming.com/tutorial/3d/quaternions.html" target="_top">http://www.cprogramming.com/tutorial/3d/quaternions.html</a></li>
 200 <li class="listitem"><a class="ulink" href="http://www.isner.com/tutorials/quatSpells/quaternion_spells_12.htm" target="_top">http://www.isner.com/tutorials/quatSpells/quaternion_spells_12.htm</a></li>
 201 <li class="listitem">
 202 3D Maths Primer for Graphics and Game Development ISBN-10: 1556229119
 203 </li>
 204 <li class="listitem"><a class="ulink" href="http://www.cs.caltech.edu/courses/cs171/quatut.pdf" target="_top">http://www.cs.caltech.edu/courses/cs171/quatut.pdf</a></li>
 205 <li class="listitem"><a class="ulink" href="http://www.j3d.org/matrix_faq/matrfaq_latest.html#Q56" target="_top">http://www.j3d.org/matrix_faq/matrfaq_latest.html#Q56</a></li>
 206 </ul></div>
 207 <p>
 208 </p>
 209 <p>
 210 @w: based on the angle of rotation it is cos(𝜃/2)
 211 @x: based on the angle of rotation and x component of the axis of
 212 rotation it is sin(𝜃/2)*axis.x
 213 @y: based on the angle of rotation and y component of the axis of
 214 rotation it is sin(𝜃/2)*axis.y
 215 @z: based on the angle of rotation and z component of the axis of
 216 rotation it is sin(𝜃/2)*axis.z
 217 </p>
 218 </div>
 219 <hr>
 220 <div class="refsect2">
 221 <a name="cogl-quaternion-init-identity"></a><h3>cogl_quaternion_init_identity ()</h3>
 222 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init_identity       (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);</pre>
 223 <p>
 224 Initializes the quaternion with the canonical quaternion identity
 225 [1 (0, 0, 0)] which represents no rotation. Multiplying a
 226 quaternion with this identity leaves the quaternion unchanged.
 227 </p>
 228 <p>
 229 You might also want to consider using
 230 <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-get-static-identity-quaternion" title="cogl_get_static_identity_quaternion ()"><code class="function">cogl_get_static_identity_quaternion()</code></a>.
 231 </p>
 232 <div class="variablelist"><table border="0">
 233 <col align="left" valign="top">
 234 <tbody><tr>
 235 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 236 <td>An uninitialized <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 237 </td>
 238 </tr></tbody>
 239 </table></div>
 240 <p class="since">Since 2.0</p>
 241 </div>
 242 <hr>
 243 <div class="refsect2">
 244 <a name="cogl-quaternion-init"></a><h3>cogl_quaternion_init ()</h3>
 245 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init                (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 246                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>,
 247                                                          <em class="parameter"><code><span class="type">float</span> x</code></em>,
 248                                                          <em class="parameter"><code><span class="type">float</span> y</code></em>,
 249                                                          <em class="parameter"><code><span class="type">float</span> z</code></em>);</pre>
 250 <p>
 251 Initializes a quaternion that rotates <em class="parameter"><code>angle</code></em> degrees around the
 252 axis vector (<em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em>, <em class="parameter"><code>z</code></em>). The axis vector does not need to be
 253 normalized.
 254 </p>
 255 <div class="variablelist"><table border="0">
 256 <col align="left" valign="top">
 257 <tbody>
 258 <tr>
 259 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 260 <td>An uninitialized <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 261 </td>
 262 </tr>
 263 <tr>
 264 <td><p><span class="term"><em class="parameter"><code>angle</code></em> :</span></p></td>
 265 <td>The angle you want to rotate around the given axis</td>
 266 </tr>
 267 <tr>
 268 <td><p><span class="term"><em class="parameter"><code>x</code></em> :</span></p></td>
 269 <td>The x component of your axis vector about which you want to
 270 rotate.</td>
 271 </tr>
 272 <tr>
 273 <td><p><span class="term"><em class="parameter"><code>y</code></em> :</span></p></td>
 274 <td>The y component of your axis vector about which you want to
 275 rotate.</td>
 276 </tr>
 277 <tr>
 278 <td><p><span class="term"><em class="parameter"><code>z</code></em> :</span></p></td>
 279 <td>The z component of your axis vector about which you want to
 280 rotate.</td>
 281 </tr>
 282 <tr>
 283 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 284 <td>A normalized, unit quaternion representing an orientation
 285 rotated <em class="parameter"><code>angle</code></em> degrees around the axis vector (<em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em>, <em class="parameter"><code>z</code></em>)</td>
 286 </tr>
 287 </tbody>
 288 </table></div>
 289 <p class="since">Since 2.0</p>
 290 </div>
 291 <hr>
 292 <div class="refsect2">
 293 <a name="cogl-quaternion-init-from-angle-vector"></a><h3>cogl_quaternion_init_from_angle_vector ()</h3>
 294 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init_from_angle_vector
 295                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 296                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>,
 297                                                          <em class="parameter"><code>const <span class="type">float</span> *axis3f</code></em>);</pre>
 298 <p>
 299 Initializes a quaternion that rotates <em class="parameter"><code>angle</code></em> degrees around the
 300 given <em class="parameter"><code>axis</code></em> vector. The axis vector does not need to be
 301 normalized.
 302 </p>
 303 <div class="variablelist"><table border="0">
 304 <col align="left" valign="top">
 305 <tbody>
 306 <tr>
 307 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 308 <td>An uninitialized <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 309 </td>
 310 </tr>
 311 <tr>
 312 <td><p><span class="term"><em class="parameter"><code>axis3f</code></em> :</span></p></td>
 313 <td>your 3 component axis vector about which you want to rotate.</td>
 314 </tr>
 315 <tr>
 316 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 317 <td>A normalized, unit quaternion representing an orientation
 318 rotated <em class="parameter"><code>angle</code></em> degrees around the given <em class="parameter"><code>axis</code></em> vector.</td>
 319 </tr>
 320 </tbody>
 321 </table></div>
 322 <p class="since">Since 2.0</p>
 323 </div>
 324 <hr>
 325 <div class="refsect2">
 326 <a name="cogl-quaternion-init-from-array"></a><h3>cogl_quaternion_init_from_array ()</h3>
 327 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init_from_array     (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 328                                                          <em class="parameter"><code>const <span class="type">float</span> *array</code></em>);</pre>
 329 <p>
 330 Initializes a [w (x, y,z)] quaternion directly from an array of 4
 331 floats: [w,x,y,z].
 332 </p>
 333 <div class="variablelist"><table border="0">
 334 <col align="left" valign="top">
 335 <tbody>
 336 <tr>
 337 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 338 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 339 </td>
 340 </tr>
 341 <tr>
 342 <td><p><span class="term"><em class="parameter"><code>array</code></em> :</span></p></td>
 343 <td>An array of 4 floats (x,y,z),w</td>
 344 </tr>
 345 </tbody>
 346 </table></div>
 347 <p class="since">Since 2.0</p>
 348 </div>
 349 <hr>
 350 <div class="refsect2">
 351 <a name="cogl-quaternion-init-from-x-rotation"></a><h3>cogl_quaternion_init_from_x_rotation ()</h3>
 352 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init_from_x_rotation
 353                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 354                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>);</pre>
 355 <p>
 356 XXX: check which direction this rotates
 357 </p>
 358 <div class="variablelist"><table border="0">
 359 <col align="left" valign="top">
 360 <tbody>
 361 <tr>
 362 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 363 <td>An uninitialized <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 364 </td>
 365 </tr>
 366 <tr>
 367 <td><p><span class="term"><em class="parameter"><code>angle</code></em> :</span></p></td>
 368 <td>The angle to rotate around the x axis</td>
 369 </tr>
 370 </tbody>
 371 </table></div>
 372 <p class="since">Since 2.0</p>
 373 </div>
 374 <hr>
 375 <div class="refsect2">
 376 <a name="cogl-quaternion-init-from-y-rotation"></a><h3>cogl_quaternion_init_from_y_rotation ()</h3>
 377 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init_from_y_rotation
 378                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 379                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>);</pre>
 380 <div class="variablelist"><table border="0">
 381 <col align="left" valign="top">
 382 <tbody>
 383 <tr>
 384 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 385 <td>An uninitialized <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 386 </td>
 387 </tr>
 388 <tr>
 389 <td><p><span class="term"><em class="parameter"><code>angle</code></em> :</span></p></td>
 390 <td>The angle to rotate around the y axis</td>
 391 </tr>
 392 </tbody>
 393 </table></div>
 394 <p class="since">Since 2.0</p>
 395 </div>
 396 <hr>
 397 <div class="refsect2">
 398 <a name="cogl-quaternion-init-from-z-rotation"></a><h3>cogl_quaternion_init_from_z_rotation ()</h3>
 399 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_init_from_z_rotation
 400                                                         (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 401                                                          <em class="parameter"><code><span class="type">float</span> angle</code></em>);</pre>
 402 <div class="variablelist"><table border="0">
 403 <col align="left" valign="top">
 404 <tbody>
 405 <tr>
 406 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 407 <td>An uninitialized <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 408 </td>
 409 </tr>
 410 <tr>
 411 <td><p><span class="term"><em class="parameter"><code>angle</code></em> :</span></p></td>
 412 <td>The angle to rotate around the y axis</td>
 413 </tr>
 414 </tbody>
 415 </table></div>
 416 <p class="since">Since 2.0</p>
 417 </div>
 418 <hr>
 419 <div class="refsect2">
 420 <a name="cogl-quaternion-equal"></a><h3>cogl_quaternion_equal ()</h3>
 421 <pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>            cogl_quaternion_equal               (<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gconstpointer"><span class="type">gconstpointer</span></a> v1</code></em>,
 422                                                          <em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gconstpointer"><span class="type">gconstpointer</span></a> v2</code></em>);</pre>
 423 <p>
 424 Compares that all the components of quaternions <em class="parameter"><code>a</code></em> and <em class="parameter"><code>b</code></em> are
 425 equal.
 426 </p>
 427 <p>
 428 An epsilon value is not used to compare the float components, but
 429 the == operator is at least used so that 0 and -0 are considered
 430 equal.
 431 </p>
 432 <div class="variablelist"><table border="0">
 433 <col align="left" valign="top">
 434 <tbody>
 435 <tr>
 436 <td><p><span class="term"><em class="parameter"><code>v1</code></em> :</span></p></td>
 437 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 438 </td>
 439 </tr>
 440 <tr>
 441 <td><p><span class="term"><em class="parameter"><code>v2</code></em> :</span></p></td>
 442 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 443 </td>
 444 </tr>
 445 <tr>
 446 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 447 <td>
 448 <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if the quaternions are equal else <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a>.</td>
 449 </tr>
 450 </tbody>
 451 </table></div>
 452 <p class="since">Since 2.0</p>
 453 </div>
 454 <hr>
 455 <div class="refsect2">
 456 <a name="cogl-quaternion-copy"></a><h3>cogl_quaternion_copy ()</h3>
 457 <pre class="programlisting"><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="returnvalue">CoglQuaternion</span></a> *    cogl_quaternion_copy                (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *src</code></em>);</pre>
 458 <p>
 459 Allocates a new <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> on the stack and initializes it with
 460 the same values as <em class="parameter"><code>src</code></em>.
 461 </p>
 462 <div class="variablelist"><table border="0">
 463 <col align="left" valign="top">
 464 <tbody>
 465 <tr>
 466 <td><p><span class="term"><em class="parameter"><code>src</code></em> :</span></p></td>
 467 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 468 </td>
 469 </tr>
 470 <tr>
 471 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 472 <td>A newly allocated <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> which should be freed
 473 using <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-free" title="cogl_quaternion_free ()"><code class="function">cogl_quaternion_free()</code></a>
 474 </td>
 475 </tr>
 476 </tbody>
 477 </table></div>
 478 <p class="since">Since 2.0</p>
 479 </div>
 480 <hr>
 481 <div class="refsect2">
 482 <a name="cogl-quaternion-free"></a><h3>cogl_quaternion_free ()</h3>
 483 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_free                (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);</pre>
 484 <p>
 485 Frees a <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> that was previously allocated via
 486 <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-copy" title="cogl_quaternion_copy ()"><code class="function">cogl_quaternion_copy()</code></a>.
 487 </p>
 488 <div class="variablelist"><table border="0">
 489 <col align="left" valign="top">
 490 <tbody><tr>
 491 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 492 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 493 </td>
 494 </tr></tbody>
 495 </table></div>
 496 <p class="since">Since 2.0</p>
 497 </div>
 498 <hr>
 499 <div class="refsect2">
 500 <a name="cogl-quaternion-get-rotation-angle"></a><h3>cogl_quaternion_get_rotation_angle ()</h3>
 501 <pre class="programlisting"><span class="returnvalue">float</span>               cogl_quaternion_get_rotation_angle  (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);</pre>
 502 <div class="variablelist"><table border="0">
 503 <col align="left" valign="top">
 504 <tbody><tr>
 505 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 506 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 507 </td>
 508 </tr></tbody>
 509 </table></div>
 510 <p class="since">Since 2.0</p>
 511 </div>
 512 <hr>
 513 <div class="refsect2">
 514 <a name="cogl-quaternion-get-rotation-axis"></a><h3>cogl_quaternion_get_rotation_axis ()</h3>
 515 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_get_rotation_axis   (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 516                                                          <em class="parameter"><code><span class="type">float</span> *vector3</code></em>);</pre>
 517 <div class="variablelist"><table border="0">
 518 <col align="left" valign="top">
 519 <tbody><tr>
 520 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 521 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 522 </td>
 523 </tr></tbody>
 524 </table></div>
 525 <p class="since">Since 2.0</p>
 526 </div>
 527 <hr>
 528 <div class="refsect2">
 529 <a name="cogl-quaternion-normalize"></a><h3>cogl_quaternion_normalize ()</h3>
 530 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_normalize           (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);</pre>
 531 <div class="variablelist"><table border="0">
 532 <col align="left" valign="top">
 533 <tbody><tr>
 534 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 535 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 536 </td>
 537 </tr></tbody>
 538 </table></div>
 539 <p class="since">Since 2.0</p>
 540 </div>
 541 <hr>
 542 <div class="refsect2">
 543 <a name="cogl-quaternion-dot-product"></a><h3>cogl_quaternion_dot_product ()</h3>
 544 <pre class="programlisting"><span class="returnvalue">float</span>               cogl_quaternion_dot_product         (<em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
 545                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>);</pre>
 546 <div class="variablelist"><table border="0">
 547 <col align="left" valign="top">
 548 <tbody>
 549 <tr>
 550 <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td>
 551 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 552 </td>
 553 </tr>
 554 <tr>
 555 <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td>
 556 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 557 </td>
 558 </tr>
 559 </tbody>
 560 </table></div>
 561 <p class="since">Since 2.0</p>
 562 </div>
 563 <hr>
 564 <div class="refsect2">
 565 <a name="cogl-quaternion-invert"></a><h3>cogl_quaternion_invert ()</h3>
 566 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_invert              (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);</pre>
 567 <div class="variablelist"><table border="0">
 568 <col align="left" valign="top">
 569 <tbody><tr>
 570 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 571 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 572 </td>
 573 </tr></tbody>
 574 </table></div>
 575 <p class="since">Since 2.0</p>
 576 </div>
 577 <hr>
 578 <div class="refsect2">
 579 <a name="cogl-quaternion-multiply"></a><h3>cogl_quaternion_multiply ()</h3>
 580 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_multiply            (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
 581                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *left</code></em>,
 582                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *right</code></em>);</pre>
 583 <p>
 584 This combines the rotations of two quaternions into <em class="parameter"><code>result</code></em>. The
 585 operation is not commutative so the order is important because AxB
 586 != BxA. Cogl follows the standard convention for quaternions here
 587 so the rotations are applied <em class="parameter"><code>right</code></em> to <em class="parameter"><code>left</code></em>. This is similar to the
 588 combining of matrices.
 589 </p>
 590 <div class="variablelist"><table border="0">
 591 <col align="left" valign="top">
 592 <tbody>
 593 <tr>
 594 <td><p><span class="term"><em class="parameter"><code>result</code></em> :</span></p></td>
 595 <td>The destination <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 596 </td>
 597 </tr>
 598 <tr>
 599 <td><p><span class="term"><em class="parameter"><code>left</code></em> :</span></p></td>
 600 <td>The second <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> rotation to apply</td>
 601 </tr>
 602 <tr>
 603 <td><p><span class="term"><em class="parameter"><code>right</code></em> :</span></p></td>
 604 <td>The first <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> rotation to apply</td>
 605 </tr>
 606 </tbody>
 607 </table></div>
 608 <p class="since">Since 2.0</p>
 609 </div>
 610 <hr>
 611 <div class="refsect2">
 612 <a name="cogl-quaternion-pow"></a><h3>cogl_quaternion_pow ()</h3>
 613 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_pow                 (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>,
 614                                                          <em class="parameter"><code><span class="type">float</span> exponent</code></em>);</pre>
 615 <div class="variablelist"><table border="0">
 616 <col align="left" valign="top">
 617 <tbody><tr>
 618 <td><p><span class="term"><em class="parameter"><code>quaternion</code></em> :</span></p></td>
 619 <td>A <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 620 </td>
 621 </tr></tbody>
 622 </table></div>
 623 <p class="since">Since 2.0</p>
 624 </div>
 625 <hr>
 626 <div class="refsect2">
 627 <a name="cogl-quaternion-slerp"></a><h3>cogl_quaternion_slerp ()</h3>
 628 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_slerp               (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
 629                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
 630                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>,
 631                                                          <em class="parameter"><code><span class="type">float</span> t</code></em>);</pre>
 632 <p>
 633 Performs a spherical linear interpolation between two quaternions.
 634 </p>
 635 <p>
 636 Noteable properties:
 637 </p>
 638 <div class="itemizedlist"><ul class="itemizedlist" type="disc">
 639 <li class="listitem">
 640 commutative: No
 641 </li>
 642 <li class="listitem">
 643 constant velocity: Yes
 644 </li>
 645 <li class="listitem">
 646 torque minimal (travels along the surface of the 4-sphere): Yes
 647 </li>
 648 <li class="listitem">
 649 more expensive than <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-nlerp" title="cogl_quaternion_nlerp ()"><code class="function">cogl_quaternion_nlerp()</code></a>
 650 </li>
 651 </ul></div>
 652 <p>
 653 </p>
 654 </div>
 655 <hr>
 656 <div class="refsect2">
 657 <a name="cogl-quaternion-nlerp"></a><h3>cogl_quaternion_nlerp ()</h3>
 658 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_nlerp               (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
 659                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
 660                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>,
 661                                                          <em class="parameter"><code><span class="type">float</span> t</code></em>);</pre>
 662 <p>
 663 Performs a normalized linear interpolation between two quaternions.
 664 That is it does a linear interpolation of the quaternion components
 665 and then normalizes the result. This will follow the shortest arc
 666 between the two orientations (just like the <code class="function">slerp()</code> function) but
 667 will not progress at a constant speed. Unlike <code class="function">slerp()</code> nlerp is
 668 commutative which is useful if you are blending animations
 669 together. (I.e. nlerp (tmp, a, b) followed by nlerp (result, tmp,
 670 d) is the same as nlerp (tmp, a, d) followed by nlerp (result, tmp,
 671 b)). Finally nlerp is cheaper than slerp so it can be a good choice
 672 if you don't need the constant speed property of the <code class="function">slerp()</code> function.
 673 </p>
 674 <p>
 675 Notable properties:
 676 </p>
 677 <div class="itemizedlist"><ul class="itemizedlist" type="disc">
 678 <li class="listitem">
 679 commutative: Yes
 680 </li>
 681 <li class="listitem">
 682 constant velocity: No
 683 </li>
 684 <li class="listitem">
 685 torque minimal (travels along the surface of the 4-sphere): Yes
 686 </li>
 687 <li class="listitem">
 688 faster than <a class="link" href="cogl-Quaternions-(Rotations).html#cogl-quaternion-slerp" title="cogl_quaternion_slerp ()"><code class="function">cogl_quaternion_slerp()</code></a>
 689 </li>
 690 </ul></div>
 691 <p>
 692 </p>
 693 <div class="variablelist"><table border="0">
 694 <col align="left" valign="top">
 695 <tbody>
 696 <tr>
 697 <td><p><span class="term"><em class="parameter"><code>result</code></em> :</span></p></td>
 698 <td>The destination <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 699 </td>
 700 </tr>
 701 <tr>
 702 <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td>
 703 <td>The first <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 704 </td>
 705 </tr>
 706 <tr>
 707 <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td>
 708 <td>The second <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a>
 709 </td>
 710 </tr>
 711 <tr>
 712 <td><p><span class="term"><em class="parameter"><code>t</code></em> :</span></p></td>
 713 <td>The factor in the range [0,1] used to interpolate between
 714 quaterion <em class="parameter"><code>a</code></em> and <em class="parameter"><code>b</code></em>.</td>
 715 </tr>
 716 </tbody>
 717 </table></div>
 718 </div>
 719 <hr>
 720 <div class="refsect2">
 721 <a name="cogl-quaternion-squad"></a><h3>cogl_quaternion_squad ()</h3>
 722 <pre class="programlisting"><span class="returnvalue">void</span>                cogl_quaternion_squad               (<em class="parameter"><code><a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *result</code></em>,
 723                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *prev</code></em>,
 724                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *a</code></em>,
 725                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *b</code></em>,
 726                                                          <em class="parameter"><code>const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *next</code></em>,
 727                                                          <em class="parameter"><code><span class="type">float</span> t</code></em>);</pre>
 728 <p class="since">Since 2.0</p>
 729 </div>
 730 <hr>
 731 <div class="refsect2">
 732 <a name="cogl-get-static-identity-quaternion"></a><h3>cogl_get_static_identity_quaternion ()</h3>
 733 <pre class="programlisting">const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="returnvalue">CoglQuaternion</span></a> * cogl_get_static_identity_quaternion
 734                                                         (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
 735 <p>
 736 Returns a pointer to a singleton quaternion constant describing the
 737 canonical identity [1 (0, 0, 0)] which represents no rotation.
 738 </p>
 739 <p>
 740 If you multiply a quaternion with the identity quaternion you will
 741 get back the same value as the original quaternion.
 742 </p>
 743 <div class="variablelist"><table border="0">
 744 <col align="left" valign="top">
 745 <tbody><tr>
 746 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 747 <td>A pointer to an identity quaternion</td>
 748 </tr></tbody>
 749 </table></div>
 750 <p class="since">Since 2.0</p>
 751 </div>
 752 <hr>
 753 <div class="refsect2">
 754 <a name="cogl-get-static-zero-quaternion"></a><h3>cogl_get_static_zero_quaternion ()</h3>
 755 <pre class="programlisting">const <a class="link" href="cogl-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="returnvalue">CoglQuaternion</span></a> * cogl_get_static_zero_quaternion  (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
 756 <div class="variablelist"><table border="0">
 757 <col align="left" valign="top">
 758 <tbody><tr>
 759 <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
 760 <td>a pointer to a singleton quaternion constant describing a
 761 rotation of 180 degrees around a degenerate axis:
 762 [0 (0, 0, 0)]</td>
 763 </tr></tbody>
 764 </table></div>
 765 <p class="since">Since 2.0</p>
 766 </div>
 767 </div>
 768 </div>
 769 <div class="footer">
 770 <hr>
 771           Generated by GTK-Doc V1.18.1</div>
 772 </body>
 773 </html>