97f515985d
git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@2 fdac6126-5c0c-442c-9429-916003d36597
136 lines
4.0 KiB
Plaintext
136 lines
4.0 KiB
Plaintext
/** \page tutorial_05 Using standard properties
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This example shows:
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- How to add and remove a standard property,
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- How to get and set the value of a standard property.
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As we already have seen, we can bind additional data to the mesh
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entities by means of properties. %OpenMesh provides a set of so-called
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standard properties. Unlike the custom properties these have some
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special features and a different interface, which are the matter in this
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tutorial.
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The following table lists all available standard properties and the suitable
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entity for which it can be used.
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<table>
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<tr>
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<td> </td>
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<td>Vertex</td>
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<td>Face</td>
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<td>Edge</td>
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<td>Halfedge</td>
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</tr>
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<tr>
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<td>Color</td>
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<td>X</td>
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<td>X</td>
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<td> </td>
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<td> </td>
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</tr>
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<tr>
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<td>Normal</td>
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<td>X</td>
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<td>X</td>
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<td> </td>
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<td> </td>
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</tr>
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<tr>
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<td>Position <sup> (*) </sup> </td>
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<td>X</td>
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<td> </td>
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<td> </td>
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<td> </td>
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</tr>
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<tr>
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<td>Status</td>
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<td>X</td>
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<td>X</td>
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<td>X</td>
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<td>X</td>
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</tr>
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<tr>
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<td>TexCoord</td>
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<td>X</td>
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<td> </td>
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<td> </td>
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<td> </td>
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</tr>
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</table>
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To add a standard property to an entity simply use the appropriate
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request method, e.g. \c request_face_normal(). The only exception is
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the position <sup>(*)</sup>. It cannot be added because it is
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permanently available, hence it cannot be removed as well.
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In this example we
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-# add vertex normals to a mesh object
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-# load a file
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-# check if the file provides vertex normals and calculate them if not
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-# move every vertex one unit length along its normal direction
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-# print the resulting positions to std::cout
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Let's start with adding vertex normals to the mesh:
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\dontinclude 05-std_properties/properties.cc
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\skipline request_vertex_normals
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In a similar manner we can request the other standard properties. For example
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the face normals:
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\skipline request_face_normals
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We need them to calculate the vertex normals with \c update_normals(), if the
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file didn't provide any.
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But we can do more with standard properties. We can verify if the mesh
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has already the property vertex normals
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\dontinclude 05-std_properties/properties.cc
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\skipline has_vertex_normals
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\until }
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And after usage we remove them again
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\skipline release_vertex_normals
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But, what happens if for example the vertex status property has been
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requested twice? Then the first release does nothing, but the second
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one will remove it. The standard properties have a reference counter,
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which is incremented by one for each request and decremented by one
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for each release. If the counter reaches 0 the property will be
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removed from memory.
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Now we know how to add and remove standard properties, but how do we
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access them? Again we need the mesh object. Unlike the custom
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properties, where we accessed one with the mesh member function \c
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property(), for each standard property the mesh provides a get and a
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set method. We have used one pair of get/set methods already in the
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previous three tutorials, where we computed a new location for the
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vertex position. Here we move all vertices a unit length along their
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normal direction:
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\dontinclude 05-std_properties/properties.cc
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\skipline MyMesh::VertexIter
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\until {
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\skipline mesh.set_point
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\skipline }
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The get-methods take an entity handle and return the value of
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the desired property, and the set-methods require an additional
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parameter to pass the new value to the property. According to the
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table not every pair of get/set-methods apply to every entity. For
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example a face has normally no texture coordinates, hence a call to \c
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mesh.texcoord( _face_handle ) will result in an error when compiling
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the code.
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Since we know how to add/remove/access standard properties, one further
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question remains. What data types do they have? And are there more hidden
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secrets? The next tutorial (\ref tutorial_06) will give the answer.
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The complete source looks like this:
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\include 05-std_properties/properties.cc
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*/ |