7aab2ad475
git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@819 fdac6126-5c0c-442c-9429-916003d36597
126 lines
4.2 KiB
Plaintext
126 lines
4.2 KiB
Plaintext
/** \page tutorial_08 Using IO::Options
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This example shows:
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- How to control the behaviour of \c Mesh::IO::read_mesh(),
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- How to control the behaviour of \c Mesh::IO::write_mesh().
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The class \c OpenMesh::IO::Options can be used when reading/writing a
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mesh. It controls the behaviour of the reader/writer modules by means
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of enabled/disabled bits in a bitset. The class provides an interface
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for enabling, disabling and verifying the bits in the set. We
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distinguish between
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-# mode bits - control binary reading/writing
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- Options::Binary
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- Options::MSB
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- Options::LSB
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- Options::Swap (MSB|LSB)
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-# property bits - controls which standard properties to read/write
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- Options::VertexNormal
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- Options::VertexTexCoord
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- Options::VertexColor
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- Options::FaceNormal
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- Options::FaceColor
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- Options::ColorAlpha
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- Options::ColorFloat
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These bits have different effects when reading or writing. The file
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format itself is selected by the extension of the filename. The IO
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subsystem of the %OpenMesh library supports currently four
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formats. The following table list all formats and indicates whether
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the format supports ASCII/binary storage with the apropiate extension.
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<table border=0>
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<tr>
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<td>Format</td><td colspan=2>Ascii</td><td>Binary</td>
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</tr><tr>
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<td>OFF</td><td>.off</td><td>.off</td>
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</tr><tr>
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<td>OBJ</td><td>.obj</td><td></td>
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</tr><tr>
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<td>STL</td><td>.stla, .stl</td><td>.stlb, .stl</td>
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</tr><tr>
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<td>OM</td><td></td><td>.om</td>
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</tr>
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</table>
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The program does not more than providing a command line based
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interface to select the option bits for reading/writing and to request
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mesh properties. Hence illegal combinations are possible and will
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result in a failure of the program. (The input file won't be damaged
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in this case, but be careful where you put the ouput file!)
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Please note that the Options::ColorFloat is currently only implemented for PLY
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and OFF files.
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<h5>Reading meshes</h5>
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When reading a file the mode bits are used to give the reader an
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advice or hint. Depending on the format we can help the reader to
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interpret the data correctly. First of all we can tell it that the
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file contains binary data.
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\dontinclude 08-io_options/io_options.cc
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\skipline ropt += IO::Options::Binary
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Further on we can ask the reader two swap the byte-order.
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\skipline ropt += IO::Options::Swap
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(Both can be done via the command line with the options -b and -s,
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respectively.)
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By default the geometry and the topology is restored from the
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file. The file might contain more, especially it could provide normals
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or texture coordinates. We can examine the property bits after
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reading to find out what else is available:
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\dontinclude 08-io_options/io_options.cc
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\skipline ropt.check(IO::Options::VertexNormal)
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If a property bit is set it does not mean, that it has been restored
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as well. The property must have been requested prior reading the
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file. (The demo program offers the command line option \c -Xv[nct] and
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\c -Xf[nc] to request vertex and face properties.)
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<h5>Writing meshes</h5>
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When writing the mesh the mode bits apparently control whether to use
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the binary variant and the desired byte-ordering. For example, if we
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choose binary mode and want to swap the byte order, we set
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\skipline wopt += IO::Options::Binary
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\skipline wopt += IO::Options::Swap
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If the format does not specify the byte order the system byte order is
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used. If the format does not support binary storage, the mode bits are
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ignored.
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If the format supports storing additional information, which are
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conform with the standard properties, we can use the property bits to
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tell the writer what we would like to have stored. If we would like to
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store the vertex normals we simply set
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\skipline wopt += IO::Options::VertexNormal
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Finally we can write the data to the file
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\dontinclude 08-io_options/io_options.cc
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\skipline write_mesh
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The method returns false on error, which might have three different reasons:
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-# the option is not supported by the choosen format
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-# a selected standard property is not available
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-# a 'system' error like
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- could not open the file due to access rights
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- disk space exhausted during write
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- ...
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The complete source looks like this:
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\include 08-io_options/io_options.cc
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*/
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