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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Matrices: Cogl Reference Manual</title>
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<a href="#cogl-Matrices.description" class="shortcut">Description</a></span>
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<div class="refentry">
<a name="cogl-Matrices"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="cogl-Matrices.top_of_page"></a>Matrices</span></h2>
<p>Matrices — Functions for initializing and manipulating 4x4 matrices</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="cogl-Matrices.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_proto_type">
<col class="functions_proto_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-init-identity" title="cogl_matrix_init_identity ()">cogl_matrix_init_identity</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="returnvalue">CoglMatrix</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-copy" title="cogl_matrix_copy ()">cogl_matrix_copy</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">CoglBool</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-equal" title="cogl_matrix_equal ()">cogl_matrix_equal</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-free" title="cogl_matrix_free ()">cogl_matrix_free</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-frustum" title="cogl_matrix_frustum ()">cogl_matrix_frustum</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-ortho" title="cogl_matrix_ortho ()">cogl_matrix_ortho</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-perspective" title="cogl_matrix_perspective ()">cogl_matrix_perspective</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-multiply" title="cogl_matrix_multiply ()">cogl_matrix_multiply</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-rotate" title="cogl_matrix_rotate ()">cogl_matrix_rotate</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-translate" title="cogl_matrix_translate ()">cogl_matrix_translate</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-scale" title="cogl_matrix_scale ()">cogl_matrix_scale</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-transpose" title="cogl_matrix_transpose ()">cogl_matrix_transpose</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-init-from-array" title="cogl_matrix_init_from_array ()">cogl_matrix_init_from_array</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">const <span class="returnvalue">float</span> *
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-get-array" title="cogl_matrix_get_array ()">cogl_matrix_get_array</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">CoglBool</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-get-inverse" title="cogl_matrix_get_inverse ()">cogl_matrix_get_inverse</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-transform-point" title="cogl_matrix_transform_point ()">cogl_matrix_transform_point</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-project-points" title="cogl_matrix_project_points ()">cogl_matrix_project_points</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-transform-points" title="cogl_matrix_transform_points ()">cogl_matrix_transform_points</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">CoglBool</span>
</td>
<td class="function_name">
<a class="link" href="cogl-Matrices.html#cogl-matrix-is-identity" title="cogl_matrix_is_identity ()">cogl_matrix_is_identity</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-Matrices.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="other_proto_type">
<col class="other_proto_name">
</colgroup>
<tbody><tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix">CoglMatrix</a></td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-Matrices.description"></a><h2>Description</h2>
<p>Matrices are used in Cogl to describe affine model-view transforms, texture
transforms, and projective transforms. This exposes a utility API that can
be used for direct manipulation of these matrices.</p>
</div>
<div class="refsect1">
<a name="cogl-Matrices.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="cogl-matrix-init-identity"></a><h3>cogl_matrix_init_identity ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_init_identity (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Resets matrix to the identity matrix:</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
2
3
4</pre></td>
<td class="listing_code"><pre class="programlisting"><span class="p">.</span><span class="n">xx</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span> <span class="p">.</span><span class="n">xy</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">xz</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">xw</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span>
<span class="p">.</span><span class="n">yx</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">yy</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span> <span class="p">.</span><span class="n">yz</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">yw</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span>
<span class="p">.</span><span class="n">zx</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">zy</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">zz</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span> <span class="p">.</span><span class="n">zw</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span>
<span class="p">.</span><span class="n">wx</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">wy</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">wz</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="p">.</span><span class="n">ww</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p></p>
<div class="refsect3">
<a name="cogl-matrix-init-identity.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-copy"></a><h3>cogl_matrix_copy ()</h3>
<pre class="programlisting"><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="returnvalue">CoglMatrix</span></a> *
cogl_matrix_copy (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Allocates a new <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> on the heap and initializes it with
the same values as <em class="parameter"><code>matrix</code></em>
.</p>
<div class="refsect3">
<a name="cogl-matrix-copy.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix you want to copy</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-copy.returns"></a><h4>Returns</h4>
<p>A newly allocated <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> which
should be freed using <a class="link" href="cogl-Matrices.html#cogl-matrix-free" title="cogl_matrix_free ()"><code class="function">cogl_matrix_free()</code></a>. </p>
<p><span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span></p>
</div>
<p class="since">Since: <a class="link" href="ix07.html#api-index-1.6">1.6</a></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-equal"></a><h3>cogl_matrix_equal ()</h3>
<pre class="programlisting"><span class="returnvalue">CoglBool</span>
cogl_matrix_equal (<em class="parameter"><code>const <span class="type">void</span> *v1</code></em>,
<em class="parameter"><code>const <span class="type">void</span> *v2</code></em>);</pre>
<p>Compares two matrices to see if they represent the same
transformation. Although internally the matrices may have different
annotations associated with them and may potentially have a cached
inverse matrix these are not considered in the comparison.</p>
<div class="refsect3">
<a name="cogl-matrix-equal.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>v1</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>v2</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="ix06.html#api-index-1.4">1.4</a></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-free"></a><h3>cogl_matrix_free ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_free (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Frees a <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> that was previously allocated via a call to
<a class="link" href="cogl-Matrices.html#cogl-matrix-copy" title="cogl_matrix_copy ()"><code class="function">cogl_matrix_copy()</code></a>.</p>
<div class="refsect3">
<a name="cogl-matrix-free.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix you want to free</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="ix07.html#api-index-1.6">1.6</a></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-frustum"></a><h3>cogl_matrix_frustum ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_frustum (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> left</code></em>,
<em class="parameter"><code><span class="type">float</span> right</code></em>,
<em class="parameter"><code><span class="type">float</span> bottom</code></em>,
<em class="parameter"><code><span class="type">float</span> top</code></em>,
<em class="parameter"><code><span class="type">float</span> z_near</code></em>,
<em class="parameter"><code><span class="type">float</span> z_far</code></em>);</pre>
<p>Multiplies <em class="parameter"><code>matrix</code></em>
by the given frustum perspective matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-frustum.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>left</p></td>
<td class="parameter_description"><p>X position of the left clipping plane where it
intersects the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>right</p></td>
<td class="parameter_description"><p>X position of the right clipping plane where it
intersects the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>bottom</p></td>
<td class="parameter_description"><p>Y position of the bottom clipping plane where it
intersects the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>top</p></td>
<td class="parameter_description"><p>Y position of the top clipping plane where it intersects
the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_near</p></td>
<td class="parameter_description"><p>The distance to the near clipping plane (Must be positive)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_far</p></td>
<td class="parameter_description"><p>The distance to the far clipping plane (Must be positive)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-ortho"></a><h3>cogl_matrix_ortho ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_ortho (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> left</code></em>,
<em class="parameter"><code><span class="type">float</span> right</code></em>,
<em class="parameter"><code><span class="type">float</span> bottom</code></em>,
<em class="parameter"><code><span class="type">float</span> top</code></em>,
<em class="parameter"><code><span class="type">float</span> near</code></em>,
<em class="parameter"><code><span class="type">float</span> far</code></em>);</pre>
<div class="warning">
<p><code class="literal">cogl_matrix_ortho</code> has been deprecated since version 1.10 and should not be used in newly-written code.</p>
<p>Use <code class="function">cogl_matrix_orthographic()</code></p>
</div>
<p>Multiplies <em class="parameter"><code>matrix</code></em>
by a parallel projection matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-ortho.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>left</p></td>
<td class="parameter_description"><p>The coordinate for the left clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>right</p></td>
<td class="parameter_description"><p>The coordinate for the right clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>bottom</p></td>
<td class="parameter_description"><p>The coordinate for the bottom clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>top</p></td>
<td class="parameter_description"><p>The coordinate for the top clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>near</p></td>
<td class="parameter_description"><p>The <span class="emphasis"><em>distance</em></span> to the near clipping
plane (will be <span class="emphasis"><em>negative</em></span> if the plane is
behind the viewer)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>far</p></td>
<td class="parameter_description"><p>The <span class="emphasis"><em>distance</em></span> to the far clipping
plane (will be <span class="emphasis"><em>negative</em></span> if the plane is
behind the viewer)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-perspective"></a><h3>cogl_matrix_perspective ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_perspective (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> fov_y</code></em>,
<em class="parameter"><code><span class="type">float</span> aspect</code></em>,
<em class="parameter"><code><span class="type">float</span> z_near</code></em>,
<em class="parameter"><code><span class="type">float</span> z_far</code></em>);</pre>
<p>Multiplies <em class="parameter"><code>matrix</code></em>
by the described perspective matrix</p>
<div class="note">You should be careful not to have to great a <em class="parameter"><code>z_far</code></em> / <em class="parameter"><code>z_near</code></em>
ratio since that will reduce the effectiveness of depth testing
since there wont be enough precision to identify the depth of
objects near to each other.</div>
<div class="refsect3">
<a name="cogl-matrix-perspective.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>fov_y</p></td>
<td class="parameter_description"><p>Vertical field of view angle in degrees.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>aspect</p></td>
<td class="parameter_description"><p>The (width over height) aspect ratio for display</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_near</p></td>
<td class="parameter_description"><p>The distance to the near clipping plane (Must be positive,
and must not be 0)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_far</p></td>
<td class="parameter_description"><p>The distance to the far clipping plane (Must be positive)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-multiply"></a><h3>cogl_matrix_multiply ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_multiply (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *result</code></em>,
<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *a</code></em>,
<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *b</code></em>);</pre>
<p>Multiplies the two supplied matrices together and stores
the resulting matrix inside <em class="parameter"><code>result</code></em>
.</p>
<div class="note">It is possible to multiply the <em class="parameter"><code>a</code></em> matrix in-place, so
<em class="parameter"><code>result</code></em> can be equal to <em class="parameter"><code>a</code></em> but can't be equal to <em class="parameter"><code>b</code></em>.</div>
<div class="refsect3">
<a name="cogl-matrix-multiply.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>result</p></td>
<td class="parameter_description"><p>The address of a 4x4 matrix to store the result in</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>a</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>b</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-rotate"></a><h3>cogl_matrix_rotate ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_rotate (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> angle</code></em>,
<em class="parameter"><code><span class="type">float</span> x</code></em>,
<em class="parameter"><code><span class="type">float</span> y</code></em>,
<em class="parameter"><code><span class="type">float</span> z</code></em>);</pre>
<p>Multiplies <em class="parameter"><code>matrix</code></em>
with a rotation matrix that applies a rotation
of <em class="parameter"><code>angle</code></em>
degrees around the specified 3D vector.</p>
<div class="refsect3">
<a name="cogl-matrix-rotate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>angle</p></td>
<td class="parameter_description"><p>The angle you want to rotate in degrees</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p>X component of your rotation vector</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p>Y component of your rotation vector</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p>Z component of your rotation vector</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-translate"></a><h3>cogl_matrix_translate ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_translate (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> x</code></em>,
<em class="parameter"><code><span class="type">float</span> y</code></em>,
<em class="parameter"><code><span class="type">float</span> z</code></em>);</pre>
<p>Multiplies <em class="parameter"><code>matrix</code></em>
with a transform matrix that translates along
the X, Y and Z axis.</p>
<div class="refsect3">
<a name="cogl-matrix-translate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p>The X translation you want to apply</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p>The Y translation you want to apply</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p>The Z translation you want to apply</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-scale"></a><h3>cogl_matrix_scale ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_scale (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> sx</code></em>,
<em class="parameter"><code><span class="type">float</span> sy</code></em>,
<em class="parameter"><code><span class="type">float</span> sz</code></em>);</pre>
<p>Multiplies <em class="parameter"><code>matrix</code></em>
with a transform matrix that scales along the X,
Y and Z axis.</p>
<div class="refsect3">
<a name="cogl-matrix-scale.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>sx</p></td>
<td class="parameter_description"><p>The X scale factor</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>sy</p></td>
<td class="parameter_description"><p>The Y scale factor</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>sz</p></td>
<td class="parameter_description"><p>The Z scale factor</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-transpose"></a><h3>cogl_matrix_transpose ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_transpose (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Replaces <em class="parameter"><code>matrix</code></em>
with its transpose. Ie, every element (i,j) in the
new matrix is taken from element (j,i) in the old matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-transpose.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<p class="since">Since: 1.10</p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-init-from-array"></a><h3>cogl_matrix_init_from_array ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_init_from_array (<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code>const <span class="type">float</span> *array</code></em>);</pre>
<p>Initializes <em class="parameter"><code>matrix</code></em>
with the contents of <em class="parameter"><code>array</code></em>
</p>
<div class="refsect3">
<a name="cogl-matrix-init-from-array.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>array</p></td>
<td class="parameter_description"><p>A linear array of 16 floats (column-major order)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-get-array"></a><h3>cogl_matrix_get_array ()</h3>
<pre class="programlisting">const <span class="returnvalue">float</span> *
cogl_matrix_get_array (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Casts <em class="parameter"><code>matrix</code></em>
to a float array which can be directly passed to OpenGL.</p>
<div class="refsect3">
<a name="cogl-matrix-get-array.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-get-array.returns"></a><h4>Returns</h4>
<p> a pointer to the float array</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-get-inverse"></a><h3>cogl_matrix_get_inverse ()</h3>
<pre class="programlisting"><span class="returnvalue">CoglBool</span>
cogl_matrix_get_inverse (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *inverse</code></em>);</pre>
<p>Gets the inverse transform of a given matrix and uses it to initialize
a new <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a>.</p>
<div class="note">Although the first parameter is annotated as const to indicate
that the transform it represents isn't modified this function may
technically save a copy of the inverse transform within the given
<a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> so that subsequent requests for the inverse transform may
avoid costly inversion calculations.</div>
<div class="refsect3">
<a name="cogl-matrix-get-inverse.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>inverse</p></td>
<td class="parameter_description"><p>The destination for a 4x4 inverse transformation matrix. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-get-inverse.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if the inverse was successfully calculated or <code class="literal">FALSE</code>
for degenerate transformations that can't be inverted (in this case the
<em class="parameter"><code>inverse</code></em>
matrix will simply be initialized with the identity matrix)</p>
</div>
<p class="since">Since: <a class="link" href="ix05.html#api-index-1.2">1.2</a></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-transform-point"></a><h3>cogl_matrix_transform_point ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_transform_point (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">float</span> *x</code></em>,
<em class="parameter"><code><span class="type">float</span> *y</code></em>,
<em class="parameter"><code><span class="type">float</span> *z</code></em>,
<em class="parameter"><code><span class="type">float</span> *w</code></em>);</pre>
<p>Transforms a point whos position is given and returned as four float
components.</p>
<div class="refsect3">
<a name="cogl-matrix-transform-point.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A 4x4 transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p>The X component of your points position. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for input and for returning results. Default is transfer full."><span class="acronym">inout</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p>The Y component of your points position. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for input and for returning results. Default is transfer full."><span class="acronym">inout</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p>The Z component of your points position. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for input and for returning results. Default is transfer full."><span class="acronym">inout</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>w</p></td>
<td class="parameter_description"><p>The W component of your points position. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for input and for returning results. Default is transfer full."><span class="acronym">inout</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-project-points"></a><h3>cogl_matrix_project_points ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_project_points (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">int</span> n_components</code></em>,
<em class="parameter"><code><span class="type">size_t</span> stride_in</code></em>,
<em class="parameter"><code>const <span class="type">void</span> *points_in</code></em>,
<em class="parameter"><code><span class="type">size_t</span> stride_out</code></em>,
<em class="parameter"><code><span class="type">void</span> *points_out</code></em>,
<em class="parameter"><code><span class="type">int</span> n_points</code></em>);</pre>
<p>Projects an array of input points and writes the result to another
array of output points. The input points can either have 2, 3 or 4
components each. The output points always have 4 components (known
as homogenous coordinates). The output array can simply point to
the input array to do the transform in-place.</p>
<p>Here's an example with differing input/output strides:</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23</pre></td>
<td class="listing_code"><pre class="programlisting"><span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="kt">float</span> <span class="n">x</span><span class="p">,</span><span class="n">y</span><span class="p">;</span>
<span class="kt">uint8_t</span> <span class="n">r</span><span class="p">,</span><span class="n">g</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">a</span><span class="p">;</span>
<span class="kt">float</span> <span class="n">s</span><span class="p">,</span><span class="n">t</span><span class="p">,</span><span class="n">p</span><span class="p">;</span>
<span class="p">}</span> <span class="n">MyInVertex</span><span class="p">;</span>
<span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="kt">uint8_t</span> <span class="n">r</span><span class="p">,</span><span class="n">g</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">a</span><span class="p">;</span>
<span class="kt">float</span> <span class="n">x</span><span class="p">,</span><span class="n">y</span><span class="p">,</span><span class="n">z</span><span class="p">;</span>
<span class="p">}</span> <span class="n">MyOutVertex</span><span class="p">;</span>
<span class="n">MyInVertex</span> <span class="n">vertices</span><span class="p">[</span><span class="n">N_VERTICES</span><span class="p">];</span>
<span class="n">MyOutVertex</span> <span class="n">results</span><span class="p">[</span><span class="n">N_VERTICES</span><span class="p">];</span>
<span class="n">CoglMatrix</span> <span class="n">matrix</span><span class="p">;</span>
<span class="n">my_load_vertices</span> <span class="p">(</span><span class="n">vertices</span><span class="p">);</span>
<span class="n">my_get_matrix</span> <span class="p">(</span><span class="o">&</span><span class="n">matrix</span><span class="p">);</span>
<span class="n">cogl_matrix_project_points</span> <span class="p">(</span><span class="o">&</span><span class="n">matrix</span><span class="p">,</span>
<span class="mi">2</span><span class="p">,</span>
<span class="k">sizeof</span> <span class="p">(</span><span class="n">MyInVertex</span><span class="p">),</span>
<span class="o">&</span><span class="n">vertices</span><span class="p">[</span><span class="mi">0</span><span class="p">].</span><span class="n">x</span><span class="p">,</span>
<span class="k">sizeof</span> <span class="p">(</span><span class="n">MyOutVertex</span><span class="p">),</span>
<span class="o">&</span><span class="n">results</span><span class="p">[</span><span class="mi">0</span><span class="p">].</span><span class="n">x</span><span class="p">,</span>
<span class="n">N_VERTICES</span><span class="p">);</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p></p>
<div class="refsect3">
<a name="cogl-matrix-project-points.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A projection matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n_components</p></td>
<td class="parameter_description"><p>The number of position components for each input point.
(either 2, 3 or 4)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>stride_in</p></td>
<td class="parameter_description"><p>The stride in bytes between input points.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>points_in</p></td>
<td class="parameter_description"><p>A pointer to the first component of the first input point.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>stride_out</p></td>
<td class="parameter_description"><p>The stride in bytes between output points.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>points_out</p></td>
<td class="parameter_description"><p>A pointer to the first component of the first output point.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n_points</p></td>
<td class="parameter_description"><p>The number of points to transform.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="stability">Stability Level: <acronym title="Unstable interfaces are experimental or transitional. They are typically used to
give outside developers early access to new or rapidly changing technology, or
to provide an interim solution to a problem where a more general solution is
anticipated. No claims are made about either source or binary compatibility from
one minor release to the next.
The Unstable interface level is a warning that these interfaces are subject to
change without warning and should not be used in unbundled products.
Given such caveats, customer impact need not be a factor when considering
incompatible changes to an Unstable interface in a major or minor release.
Nonetheless, when such changes are introduced, the changes should still be
mentioned in the release notes for the affected release.
"><span class="acronym">Unstable</span></acronym></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-transform-points"></a><h3>cogl_matrix_transform_points ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_transform_points (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>,
<em class="parameter"><code><span class="type">int</span> n_components</code></em>,
<em class="parameter"><code><span class="type">size_t</span> stride_in</code></em>,
<em class="parameter"><code>const <span class="type">void</span> *points_in</code></em>,
<em class="parameter"><code><span class="type">size_t</span> stride_out</code></em>,
<em class="parameter"><code><span class="type">void</span> *points_out</code></em>,
<em class="parameter"><code><span class="type">int</span> n_points</code></em>);</pre>
<p>Transforms an array of input points and writes the result to
another array of output points. The input points can either have 2
or 3 components each. The output points always have 3 components.
The output array can simply point to the input array to do the
transform in-place.</p>
<p>If you need to transform 4 component points see
<a class="link" href="cogl-Matrices.html#cogl-matrix-project-points" title="cogl_matrix_project_points ()"><code class="function">cogl_matrix_project_points()</code></a>.</p>
<p>Here's an example with differing input/output strides:</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23</pre></td>
<td class="listing_code"><pre class="programlisting"><span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="kt">float</span> <span class="n">x</span><span class="p">,</span><span class="n">y</span><span class="p">;</span>
<span class="kt">uint8_t</span> <span class="n">r</span><span class="p">,</span><span class="n">g</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">a</span><span class="p">;</span>
<span class="kt">float</span> <span class="n">s</span><span class="p">,</span><span class="n">t</span><span class="p">,</span><span class="n">p</span><span class="p">;</span>
<span class="p">}</span> <span class="n">MyInVertex</span><span class="p">;</span>
<span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="kt">uint8_t</span> <span class="n">r</span><span class="p">,</span><span class="n">g</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">a</span><span class="p">;</span>
<span class="kt">float</span> <span class="n">x</span><span class="p">,</span><span class="n">y</span><span class="p">,</span><span class="n">z</span><span class="p">;</span>
<span class="p">}</span> <span class="n">MyOutVertex</span><span class="p">;</span>
<span class="n">MyInVertex</span> <span class="n">vertices</span><span class="p">[</span><span class="n">N_VERTICES</span><span class="p">];</span>
<span class="n">MyOutVertex</span> <span class="n">results</span><span class="p">[</span><span class="n">N_VERTICES</span><span class="p">];</span>
<span class="n">CoglMatrix</span> <span class="n">matrix</span><span class="p">;</span>
<span class="n">my_load_vertices</span> <span class="p">(</span><span class="n">vertices</span><span class="p">);</span>
<span class="n">my_get_matrix</span> <span class="p">(</span><span class="o">&</span><span class="n">matrix</span><span class="p">);</span>
<span class="n">cogl_matrix_transform_points</span> <span class="p">(</span><span class="o">&</span><span class="n">matrix</span><span class="p">,</span>
<span class="mi">2</span><span class="p">,</span>
<span class="k">sizeof</span> <span class="p">(</span><span class="n">MyInVertex</span><span class="p">),</span>
<span class="o">&</span><span class="n">vertices</span><span class="p">[</span><span class="mi">0</span><span class="p">].</span><span class="n">x</span><span class="p">,</span>
<span class="k">sizeof</span> <span class="p">(</span><span class="n">MyOutVertex</span><span class="p">),</span>
<span class="o">&</span><span class="n">results</span><span class="p">[</span><span class="mi">0</span><span class="p">].</span><span class="n">x</span><span class="p">,</span>
<span class="n">N_VERTICES</span><span class="p">);</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p></p>
<div class="refsect3">
<a name="cogl-matrix-transform-points.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A transformation matrix</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n_components</p></td>
<td class="parameter_description"><p>The number of position components for each input point.
(either 2 or 3)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>stride_in</p></td>
<td class="parameter_description"><p>The stride in bytes between input points.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>points_in</p></td>
<td class="parameter_description"><p>A pointer to the first component of the first input point.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>stride_out</p></td>
<td class="parameter_description"><p>The stride in bytes between output points.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>points_out</p></td>
<td class="parameter_description"><p>A pointer to the first component of the first output point.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n_points</p></td>
<td class="parameter_description"><p>The number of points to transform.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="stability">Stability Level: <acronym title="Unstable interfaces are experimental or transitional. They are typically used to
give outside developers early access to new or rapidly changing technology, or
to provide an interim solution to a problem where a more general solution is
anticipated. No claims are made about either source or binary compatibility from
one minor release to the next.
The Unstable interface level is a warning that these interfaces are subject to
change without warning and should not be used in unbundled products.
Given such caveats, customer impact need not be a factor when considering
incompatible changes to an Unstable interface in a major or minor release.
Nonetheless, when such changes are introduced, the changes should still be
mentioned in the release notes for the affected release.
"><span class="acronym">Unstable</span></acronym></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-is-identity"></a><h3>cogl_matrix_is_identity ()</h3>
<pre class="programlisting"><span class="returnvalue">CoglBool</span>
cogl_matrix_is_identity (<em class="parameter"><code>const <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Determines if the given matrix is an identity matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-is-identity.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-is-identity.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if <em class="parameter"><code>matrix</code></em>
is an identity matrix else <code class="literal">FALSE</code></p>
</div>
<p class="since">Since: <a class="link" href="ix08.html#api-index-1.8">1.8</a></p>
</div>
</div>
<div class="refsect1">
<a name="cogl-Matrices.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="CoglMatrix"></a><h3>CoglMatrix</h3>
<pre class="programlisting">typedef struct {
/* column 0 */
float xx;
float yx;
float zx;
float wx;
/* column 1 */
float xy;
float yy;
float zy;
float wy;
/* column 2 */
float xz;
float yz;
float zz;
float wz;
/* column 3 */
float xw;
float yw;
float zw;
float ww;
} CoglMatrix;
</pre>
<p>A CoglMatrix holds a 4x4 transform matrix. This is a single precision,
column-major matrix which means it is compatible with what OpenGL expects.</p>
<p>A CoglMatrix can represent transforms such as, rotations, scaling,
translation, sheering, and linear projections. You can combine these
transforms by multiplying multiple matrices in the order you want them
applied.</p>
<p>The transformation of a vertex (x, y, z, w) by a CoglMatrix is given by:</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
2
3
4</pre></td>
<td class="listing_code"><pre class="programlisting"><span class="n">x_new</span> <span class="o">=</span> <span class="n">xx</span> <span class="o">*</span> <span class="n">x</span> <span class="o">+</span> <span class="n">xy</span> <span class="o">*</span> <span class="n">y</span> <span class="o">+</span> <span class="n">xz</span> <span class="o">*</span> <span class="n">z</span> <span class="o">+</span> <span class="n">xw</span> <span class="o">*</span> <span class="n">w</span>
<span class="n">y_new</span> <span class="o">=</span> <span class="n">yx</span> <span class="o">*</span> <span class="n">x</span> <span class="o">+</span> <span class="n">yy</span> <span class="o">*</span> <span class="n">y</span> <span class="o">+</span> <span class="n">yz</span> <span class="o">*</span> <span class="n">z</span> <span class="o">+</span> <span class="n">yw</span> <span class="o">*</span> <span class="n">w</span>
<span class="n">z_new</span> <span class="o">=</span> <span class="n">zx</span> <span class="o">*</span> <span class="n">x</span> <span class="o">+</span> <span class="n">zy</span> <span class="o">*</span> <span class="n">y</span> <span class="o">+</span> <span class="n">zz</span> <span class="o">*</span> <span class="n">z</span> <span class="o">+</span> <span class="n">zw</span> <span class="o">*</span> <span class="n">w</span>
<span class="n">w_new</span> <span class="o">=</span> <span class="n">wx</span> <span class="o">*</span> <span class="n">x</span> <span class="o">+</span> <span class="n">wy</span> <span class="o">*</span> <span class="n">y</span> <span class="o">+</span> <span class="n">wz</span> <span class="o">*</span> <span class="n">z</span> <span class="o">+</span> <span class="n">ww</span> <span class="o">*</span> <span class="n">w</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p></p>
<p>Where w is normally 1</p>
<div class="note">You must consider the members of the CoglMatrix structure read only,
and all matrix modifications must be done via the cogl_matrix API. This
allows Cogl to annotate the matrices internally. Violation of this will give
undefined results. If you need to initialize a matrix with a constant other
than the identity matrix you can use <a class="link" href="cogl-Matrices.html#cogl-matrix-init-from-array" title="cogl_matrix_init_from_array ()"><code class="function">cogl_matrix_init_from_array()</code></a>.</div>
</div>
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