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Geometry package: Difference between revisions
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using templates and octave guidelines for code formatting
m (→Meshing Octave) |
Carandraug (talk | contribs) (using templates and octave guidelines for code formatting) |
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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 [http://ubuntuone.com/5pNS12ZChUXeGNBniWNa3J this SVG]. | 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 [http://ubuntuone.com/5pNS12ZChUXeGNBniWNa3J this SVG]. | ||
[[File:octave.png|200px|center]] | [[File:octave.png|200px|center]] | ||
<!-- <syntaxhighlight lang="matlab"> --> | <!-- <syntaxhighlight lang="matlab"> --> | ||
<pre> | {{Code|Loading the file as polygon compatible with geometry package|<pre> | ||
octavesvg = svg( | octavesvg = svg ("octave.svg"); | ||
ids = octavesvg.pathid(); | ids = octavesvg.pathid(); | ||
P = octavesvg.path2polygon(ids{1},12)(1:end-1,:); | P = octavesvg.path2polygon (ids{1}, 12)(1:end-1,:); | ||
P = bsxfun(@minus, P, centroid(P)); | P = bsxfun (@minus, P, centroid (P)); | ||
</pre> | </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: | 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> | {{Code|Generating mesh for plot with msh package|<pre> | ||
pkg load msh | pkg load msh | ||
filename = tmpnam (); | filename = tmpnam (); | ||
meshsize = sqrt(mean(sumsq(diff(P,1,1),2)))/2; | meshsize = sqrt (mean (sumsq (diff (P, 1, 1), 2)))/2; | ||
data2geo (P, meshsize, | data2geo (P, meshsize, "output", [filename ".geo"]); | ||
T = msh2m_gmsh(filename); | T = msh2m_gmsh (filename); | ||
</pre> | </pre>}} | ||
<!-- </syntaxhighlight> --> | <!-- </syntaxhighlight> --> | ||
To plot the generated mesh we use the function <tt>pdemesh</tt> from the [http://octave.sourceforge.net/fpl/index.html fpl] package. | To plot the generated mesh we use the function <tt>pdemesh</tt> from the [http://octave.sourceforge.net/fpl/index.html fpl] package. | ||
<pre> | |||
{{Code|Plotting mesh with fpl package|<pre> | |||
pkg load fpl | pkg load fpl | ||
pdemesh(T.p,T.e,T.t) | pdemesh (T.p, T.e, T.t) | ||
</pre> | </pre>}} | ||
[[File:octave_meshed.png|thumb|200px]] | [[File:octave_meshed.png|thumb|200px]] | ||