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Geometry package: Difference between revisions
→Loading SVG files
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== Tutorials == | == Tutorials == | ||
=== Loading SVG files === | === Loading SVG files === | ||
=== Meshing Octave === | |||
This tutorial shows the workflow to generate a triangular mesh inside an arbitrary region. | |||
This tutorial requires that you install the package [http://octave.sourceforge.net/fpl/index.html fpl] and [http://octave.sourceforge.net/msh/index.html msh] (which requires [http://geuz.org/gmsh/ Gmsh] installed in your system). Alternatively, the core function <tt>delaunay</tt> could be used (the tutorial explains how) but the result aren't so pretty. | |||
The first part of the tutorial requires an interesting shape. If you have Inkscape you can use the previous tutorial to load it into octave. Here I will be using [link-to-file this SVG]. | |||
[[File:octave.svg|thumb|200px|right]] | |||
Lets load the file: | |||
<!-- <syntaxhighlight lang="matlab"> --> | |||
<pre> | |||
octavepoly = svg('octave.svg'); | |||
ids = dc.pathid(); | |||
P = dc.path2polygon(ids{1},12)(1:end-1,:); | |||
P = bsxfun(@minus, P, centroid(P)); | |||
</pre> | |||
Now we have our SVG as a polygon compatible with the Geometry package format. You can plot the polygon using the function <tt>drawPolygon</tt>. the next step is to mesh the interior of the polygon. To do this we could just call <tt>delaunay</tt> on the polygon and be done with it, but in general such mesh wont be so nice (you will need to add interior points). A very effective way of generating a good mesh is to use the package [http://octave.sourceforge.net/msh/index.html msh], which requires [http://geuz.org/gmsh/ Gmsh] installed in your system. The function data2geo in the Geometry package makes our work very easy: | |||
</pre> | |||
pkg load msh | |||
filename = tmpnam (); | |||
meshsize = sqrt(mean(sumsq(diff(P,1,1),2)))/2; | |||
data2geo (P, meshsize, 'output', [filename '.geo']); | |||
T = msh2m_gmsh(filename); | |||
</pre> | |||
<!-- </syntaxhighlight> --> | |||
To plot the generated mesh we use the function <tt>pdemesh</tt> from the [http://octave.sourceforge.net/fpl/index.html fpl] package. | |||
<pre> | |||
pkg load fpl | |||
pdemesh(T.p,T.e,T.t) | |||
</pre> | |||
[[File:octave_meshed.svg|thumb|200px|left]] | |||
=== From piece-wise polynomial shapes to polygons === | === From piece-wise polynomial shapes to polygons === | ||