(octave.info)Plotting the Triangulation

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30.1.1 Plotting the Triangulation
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Octave has the functions ‘triplot’, ‘trimesh’, and ‘trisurf’ to plot the
Delaunay triangulation of a 2-dimensional set of points.  ‘tetramesh’
will plot the triangulation of a 3-dimensional set of points.

 -- : triplot (TRI, X, Y)
 -- : triplot (TRI, X, Y, LINESPEC)
 -- : H = triplot (...)
     Plot a 2-D triangular mesh.

     TRI is typically the output of a Delaunay triangulation over the
     grid of X, Y.  Every row of TRI represents one triangle and
     contains three indices into [X, Y] which are the vertices of the
     triangles in the x-y plane.

     The linestyle to use for the plot can be defined with the argument
     LINESPEC of the same format as the ‘plot’ command.

     The optional return value H is a graphics handle to the created
     patch object.

     See also: Note: plot, Note: trimesh, Note:
     trisurf, Note: delaunay.

 -- : trimesh (TRI, X, Y, Z, C)
 -- : trimesh (TRI, X, Y, Z)
 -- : trimesh (TRI, X, Y)
 -- : trimesh (..., PROP, VAL, ...)
 -- : H = trimesh (...)
     Plot a 3-D triangular wireframe mesh.

     In contrast to ‘mesh’, which plots a mesh using rectangles,
     ‘trimesh’ plots the mesh using triangles.

     TRI is typically the output of a Delaunay triangulation over the
     grid of X, Y.  Every row of TRI represents one triangle and
     contains three indices into [X, Y] which are the vertices of the
     triangles in the x-y plane.  Z determines the height above the
     plane of each vertex.  If no Z input is given then the triangles
     are plotted as a 2-D figure.

     The color of the trimesh is computed by linearly scaling the Z
     values to fit the range of the current colormap.  Use ‘caxis’
     and/or change the colormap to control the appearance.

     Optionally, the color of the mesh can be specified independently of
     Z by supplying C, which is a vector for colormap data, or a matrix
     with three columns for RGB data.  The number of colors specified in
     C must either equal the number of vertices in Z or the number of
     triangles in TRI.

     Any property/value pairs are passed directly to the underlying
     patch object.

     The optional return value H is a graphics handle to the created
     patch object.

     See also: Note: mesh, Note: tetramesh,
     Note: triplot, Note: trisurf, Note:
     delaunay, Note: patch, *note hidden:
     XREFhidden.

 -- : trisurf (TRI, X, Y, Z, C)
 -- : trisurf (TRI, X, Y, Z)
 -- : trisurf (..., PROP, VAL, ...)
 -- : H = trisurf (...)
     Plot a 3-D triangular surface.

     In contrast to ‘surf’, which plots a surface mesh using rectangles,
     ‘trisurf’ plots the mesh using triangles.

     TRI is typically the output of a Delaunay triangulation over the
     grid of X, Y.  Every row of TRI represents one triangle and
     contains three indices into [X, Y] which are the vertices of the
     triangles in the x-y plane.  Z determines the height above the
     plane of each vertex.

     The color of the trisurf is computed by linearly scaling the Z
     values to fit the range of the current colormap.  Use ‘caxis’
     and/or change the colormap to control the appearance.

     Optionally, the color of the mesh can be specified independently of
     Z by supplying C, which is a vector for colormap data, or a matrix
     with three columns for RGB data.  The number of colors specified in
     C must either equal the number of vertices in Z or the number of
     triangles in TRI.  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 "FaceColor" property when set
     to "flat").

     Any property/value pairs are passed directly to the underlying
     patch object.

     The optional return value H is a graphics handle to the created
     patch object.

     See also: Note: surf, Note: triplot, Note:
     trimesh, Note: delaunay, *note patch:
     XREFpatch, Note: shading.

 -- : tetramesh (T, X)
 -- : tetramesh (T, X, C)
 -- : tetramesh (..., PROPERTY, VAL, ...)
 -- : H = tetramesh (...)
     Display the tetrahedrons defined in the m-by-4 matrix T as 3-D
     patches.

     T is typically the output of a Delaunay triangulation of a 3-D set
     of points.  Every row of T contains four indices into the n-by-3
     matrix X of the vertices of a tetrahedron.  Every row in X
     represents one point in 3-D space.

     The vector C 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 C are cyclically repeated.

     Calling ‘tetramesh (..., "property", "value", ...)’ passes all
     property/value pairs directly to the patch function as additional
     arguments.

     The optional return value H is a vector of patch handles where each
     handle represents one tetrahedron in the order given by T.  A
     typical use case for H is to turn the respective patch "visible"
     property "on" or "off".

     Type ‘demo tetramesh’ to see examples on using ‘tetramesh’.

     See also: Note: trimesh, Note: delaunay,
     Note: delaunayn, Note: patch.

   The difference between ‘triplot’, and ‘trimesh’ or ‘trisurf’, is that
the former only plots the 2-dimensional triangulation itself, whereas
the second two plot the value of a function ‘f (X, Y)’.  An example of
the use of the ‘triplot’ function is

     rand ("state", 2)
     x = rand (20, 1);
     y = rand (20, 1);
     tri = delaunay (x, y);
     triplot (tri, x, y);

which plots the Delaunay triangulation of a set of random points in
2-dimensions.