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Geometry package: Difference between revisions
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</syntaxhighlight>}} | </syntaxhighlight>}} | ||
As you can see the polygon has lots of points. We need to simplify the polygon in order to obtain a mesh of reasonable size. Otherwise gmsh will have problems meshing and the result could be huge (or a segmentation fault :( ). The package geometry (> 1.5.0) comes with a simplification function that uses the [http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm Ramer-Douglas-Peucker algorithm] to reduce thenumber of points in the polygon. | As you can see the polygon has lots of points. We need to simplify the polygon in order to obtain a mesh of reasonable size. Otherwise gmsh will have problems meshing and the result could be huge (or a segmentation fault :( ). The package geometry (> 1.5.0) comes with a simplification function that uses the [http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm Ramer-Douglas-Peucker algorithm] to reduce thenumber of points in the polygon. | ||
{{Code|Symplification of a polygon compatible with geometry package|<syntaxhighlight lang=" | {{Code|Symplification of a polygon compatible with geometry package|<syntaxhighlight lang="octave" style="font-size:13px"> | ||
P = simplifypolygon(P, 'tol', 1e-3); | P = simplifypolygon(P, 'tol', 1e-3); | ||
</syntaxhighlight>}} | </syntaxhighlight>}} | ||
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The next step is to mesh the interior of the polygon. To do this we could just call {{Codeline|delaunay}} 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 {{Forge|msh}}, which requires [http://geuz.org/gmsh/ Gmsh] installed in your system. The function {{Codeline|data2geo}} in the Geometry package makes our work very easy: | The next step is to mesh the interior of the polygon. To do this we could just call {{Codeline|delaunay}} 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 {{Forge|msh}}, which requires [http://geuz.org/gmsh/ Gmsh] installed in your system. The function {{Codeline|data2geo}} in the Geometry package makes our work very easy: | ||
{{Code|Generating mesh for plot with msh package|<syntaxhighlight lang=" | {{Code|Generating mesh for plot with msh package|<syntaxhighlight lang="octave" style="font-size:13px"> | ||
pkg load msh | pkg load msh | ||
filename = tmpnam (); | filename = tmpnam (); | ||
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After this code finishes, the structure T contains our mesh. To plot the generated mesh we use the function {{Codeline|pdemesh}} from the {{Forge|fpl}} package. In general is a good idea to use the openGL render (called ''fltk'') to plot meshes. | After this code finishes, the structure T contains our mesh. To plot the generated mesh we use the function {{Codeline|pdemesh}} from the {{Forge|fpl}} package. In general is a good idea to use the openGL render (called ''fltk'') to plot meshes. | ||
{{Code|Plotting mesh with fpl package|<syntaxhighlight lang=" | {{Code|Plotting mesh with fpl package|<syntaxhighlight lang="octave" style="font-size:13px"> | ||
pkg load fpl | pkg load fpl | ||
graphics_toolkit ('fltk') | graphics_toolkit ('fltk') | ||