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<a name="Plotting-the-Triangulation"></a>
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<p>
Next: <a href="Identifying-Points-in-Triangulation.html#Identifying-Points-in-Triangulation" accesskey="n" rel="next">Identifying Points in Triangulation</a>, Up: <a href="Delaunay-Triangulation.html#Delaunay-Triangulation" accesskey="u" rel="up">Delaunay Triangulation</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Plotting-the-Triangulation-1"></a>
<h4 class="subsection">30.1.1 Plotting the Triangulation</h4>

<p>Octave has the functions <code>triplot</code>, <code>trimesh</code>, and <code>trisurf</code>
to plot the Delaunay triangulation of a 2-dimensional set of points.
<code>tetramesh</code> will plot the triangulation of a 3-dimensional set of points.
</p>
<a name="XREFtriplot"></a><dl>
<dt><a name="index-triplot"></a>: <em></em> <strong>triplot</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>)</em></dt>
<dt><a name="index-triplot-1"></a>: <em></em> <strong>triplot</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>, <var>linespec</var>)</em></dt>
<dt><a name="index-triplot-2"></a>: <em><var>h</var> =</em> <strong>triplot</strong> <em>(&hellip;)</em></dt>
<dd><p>Plot a 2-D triangular mesh.
</p>
<p><var>tri</var> is typically the output of a Delaunay triangulation over the
grid of <var>x</var>, <var>y</var>.  Every row of <var>tri</var> represents one triangle
and contains three indices into [<var>x</var>, <var>y</var>] which are the
vertices of the triangles in the x-y plane.
</p>
<p>The linestyle to use for the plot can be defined with the argument
<var>linespec</var> of the same format as the <code>plot</code> command.
</p>
<p>The optional return value <var>h</var> is a graphics handle to the created
patch object.
</p>
<p><strong>See also:</strong> <a href="Two_002dDimensional-Plots.html#XREFplot">plot</a>, <a href="#XREFtrimesh">trimesh</a>, <a href="#XREFtrisurf">trisurf</a>, <a href="Delaunay-Triangulation.html#XREFdelaunay">delaunay</a>.
</p></dd></dl>


<a name="XREFtrimesh"></a><dl>
<dt><a name="index-trimesh"></a>: <em></em> <strong>trimesh</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>, <var>z</var>, <var>c</var>)</em></dt>
<dt><a name="index-trimesh-1"></a>: <em></em> <strong>trimesh</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>, <var>z</var>)</em></dt>
<dt><a name="index-trimesh-2"></a>: <em></em> <strong>trimesh</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>)</em></dt>
<dt><a name="index-trimesh-3"></a>: <em></em> <strong>trimesh</strong> <em>(&hellip;, <var>prop</var>, <var>val</var>, &hellip;)</em></dt>
<dt><a name="index-trimesh-4"></a>: <em><var>h</var> =</em> <strong>trimesh</strong> <em>(&hellip;)</em></dt>
<dd><p>Plot a 3-D triangular wireframe mesh.
</p>
<p>In contrast to <code>mesh</code>, which plots a mesh using rectangles,
<code>trimesh</code> plots the mesh using triangles.
</p>
<p><var>tri</var> is typically the output of a Delaunay triangulation over the
grid of <var>x</var>, <var>y</var>.  Every row of <var>tri</var> represents one triangle
and contains three indices into [<var>x</var>, <var>y</var>] which are the
vertices of the triangles in the x-y plane.  <var>z</var> determines the
height above the plane of each vertex.  If no <var>z</var> input is given then
the triangles are plotted as a 2-D figure.
</p>
<p>The color of the trimesh is computed by linearly scaling the <var>z</var> values
to fit the range of the current colormap.  Use <code>caxis</code> and/or
change the colormap to control the appearance.
</p>
<p>Optionally, the color of the mesh can be specified independently of <var>z</var>
by supplying <var>c</var>, which is a vector for colormap data, or a matrix with
three columns for RGB data.  The number of colors specified in <var>c</var> must
either equal the number of vertices in <var>z</var> or the number of triangles
in <var>tri</var>.
</p>
<p>Any property/value pairs are passed directly to the underlying patch object.
</p>
<p>The optional return value <var>h</var> is a graphics handle to the created patch
object.
</p>
<p><strong>See also:</strong> <a href="Three_002dDimensional-Plots.html#XREFmesh">mesh</a>, <a href="#XREFtetramesh">tetramesh</a>, <a href="#XREFtriplot">triplot</a>, <a href="#XREFtrisurf">trisurf</a>, <a href="Delaunay-Triangulation.html#XREFdelaunay">delaunay</a>, <a href="Graphics-Objects.html#XREFpatch">patch</a>, <a href="Three_002dDimensional-Plots.html#XREFhidden">hidden</a>.
</p></dd></dl>


<a name="XREFtrisurf"></a><dl>
<dt><a name="index-trisurf"></a>: <em></em> <strong>trisurf</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>, <var>z</var>, <var>c</var>)</em></dt>
<dt><a name="index-trisurf-1"></a>: <em></em> <strong>trisurf</strong> <em>(<var>tri</var>, <var>x</var>, <var>y</var>, <var>z</var>)</em></dt>
<dt><a name="index-trisurf-2"></a>: <em></em> <strong>trisurf</strong> <em>(&hellip;, <var>prop</var>, <var>val</var>, &hellip;)</em></dt>
<dt><a name="index-trisurf-3"></a>: <em><var>h</var> =</em> <strong>trisurf</strong> <em>(&hellip;)</em></dt>
<dd><p>Plot a 3-D triangular surface.
</p>
<p>In contrast to <code>surf</code>, which plots a surface mesh using rectangles,
<code>trisurf</code> plots the mesh using triangles.
</p>
<p><var>tri</var> is typically the output of a Delaunay triangulation over the
grid of <var>x</var>, <var>y</var>.  Every row of <var>tri</var> represents one triangle
and contains three indices into [<var>x</var>, <var>y</var>] which are the vertices of
the triangles in the x-y plane.  <var>z</var> determines the height above the
plane of each vertex.
</p>
<p>The color of the trisurf is computed by linearly scaling the <var>z</var> values
to fit the range of the current colormap.  Use <code>caxis</code> and/or change
the colormap to control the appearance.
</p>
<p>Optionally, the color of the mesh can be specified independently of <var>z</var>
by supplying <var>c</var>, which is a vector for colormap data, or a matrix with
three columns for RGB data.  The number of colors specified in <var>c</var> must
either equal the number of vertices in <var>z</var> or the number of triangles
in <var>tri</var>.  When specifying the color at each vertex the triangle will
be colored according to the color of the first vertex only (see patch
documentation and the <code>&quot;FaceColor&quot;</code> property when set to
<code>&quot;flat&quot;</code>).
</p>
<p>Any property/value pairs are passed directly to the underlying patch object.
</p>
<p>The optional return value <var>h</var> is a graphics handle to the created patch
object.
</p>
<p><strong>See also:</strong> <a href="Three_002dDimensional-Plots.html#XREFsurf">surf</a>, <a href="#XREFtriplot">triplot</a>, <a href="#XREFtrimesh">trimesh</a>, <a href="Delaunay-Triangulation.html#XREFdelaunay">delaunay</a>, <a href="Graphics-Objects.html#XREFpatch">patch</a>, <a href="Three_002dDimensional-Plots.html#XREFshading">shading</a>.
</p></dd></dl>


<a name="XREFtetramesh"></a><dl>
<dt><a name="index-tetramesh"></a>: <em></em> <strong>tetramesh</strong> <em>(<var>T</var>, <var>X</var>)</em></dt>
<dt><a name="index-tetramesh-1"></a>: <em></em> <strong>tetramesh</strong> <em>(<var>T</var>, <var>X</var>, <var>C</var>)</em></dt>
<dt><a name="index-tetramesh-2"></a>: <em></em> <strong>tetramesh</strong> <em>(&hellip;, <var>property</var>, <var>val</var>, &hellip;)</em></dt>
<dt><a name="index-tetramesh-3"></a>: <em><var>h</var> =</em> <strong>tetramesh</strong> <em>(&hellip;)</em></dt>
<dd><p>Display the tetrahedrons defined in the m-by-4 matrix <var>T</var> as 3-D
patches.
</p>
<p><var>T</var> is typically the output of a Delaunay triangulation of a 3-D set
of points.  Every row of <var>T</var> contains four indices into the n-by-3
matrix <var>X</var> of the vertices of a tetrahedron.  Every row in <var>X</var>
represents one point in 3-D space.
</p>
<p>The vector <var>C</var> specifies the color of each tetrahedron as an index
into the current colormap.  The default value is 1:m where m is the number
of tetrahedrons; the indices are scaled to map to the full range of the
colormap.  If there are more tetrahedrons than colors in the colormap then
the values in <var>C</var> are cyclically repeated.
</p>
<p>Calling <code>tetramesh (&hellip;, &quot;property&quot;, &quot;value&quot;, &hellip;)</code> passes all
property/value pairs directly to the patch function as additional arguments.
</p>
<p>The optional return value <var>h</var> is a vector of patch handles where each
handle represents one tetrahedron in the order given by <var>T</var>.
A typical use case for <var>h</var> is to turn the respective patch
<code>&quot;visible&quot;</code> property <code>&quot;on&quot;</code> or <code>&quot;off&quot;</code>.
</p>
<p>Type <code>demo tetramesh</code> to see examples on using <code>tetramesh</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFtrimesh">trimesh</a>, <a href="Delaunay-Triangulation.html#XREFdelaunay">delaunay</a>, <a href="Delaunay-Triangulation.html#XREFdelaunayn">delaunayn</a>, <a href="Graphics-Objects.html#XREFpatch">patch</a>.
</p></dd></dl>


<p>The difference between <code>triplot</code>, and <code>trimesh</code> or <code>trisurf</code>,
is that the former only plots the 2-dimensional triangulation itself, whereas
the second two plot the value of a function <code>f (<var>x</var>, <var>y</var>)</code>.  An
example of the use of the <code>triplot</code> function is
</p>
<div class="example">
<pre class="example">rand (&quot;state&quot;, 2)
x = rand (20, 1);
y = rand (20, 1);
tri = delaunay (x, y);
triplot (tri, x, y);
</pre></div>

<p>which plots the Delaunay triangulation of a set of random points in
2-dimensions.
The output of the above can be seen in <a href="#fig_003atriplot">Figure 30.2</a>.
</p>
<div class="float"><a name="fig_003atriplot"></a>
<div align="center"><img src="triplot.png" alt="triplot">
</div>
<div class="float-caption"><p><strong>Figure 30.2: </strong>Delaunay triangulation of a random set of points</p></div></div>
<hr>
<div class="header">
<p>
Next: <a href="Identifying-Points-in-Triangulation.html#Identifying-Points-in-Triangulation" accesskey="n" rel="next">Identifying Points in Triangulation</a>, Up: <a href="Delaunay-Triangulation.html#Delaunay-Triangulation" accesskey="u" rel="up">Delaunay Triangulation</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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