90 lines
3.5 KiB
Plaintext
90 lines
3.5 KiB
Plaintext
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//-----------------------------------------------------------------------------
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/** \page decimater_docu Mesh Decimation Framework
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The mesh decimation framework has 3 building blocks.
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-# \ref DecimaterAlg
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-# \ref DecimaterMod
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-# \ref DecimaterHnd
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\section DecimaterAlg The decimation algorithm
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The decimater (OpenMesh::Decimater::DecimaterT) provides the
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decimation algorithm, while the decimation modules provide the
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computational part. The modules compute a priority value due to some
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error metric, which is used by the decimater to feed a priority
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queue. The lower the error value, the more a potential collapse
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moves to the front of the queue. The one with the lowest error will
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always be the candidate for the next collapse.
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This implementation does a halfedge collapse, hence simply
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collapsing one vertex into another connected by a halfedge.
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\note The decimater ignores all 'locked' and 'deleted' vertices (see
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OpenMesh::Attributes::StatusBits)
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\attention The decimater sets temporarily the status bit 'tagged' and
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clears it after usage regardless of a previous state.
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\section DecimaterMod Decimating Modules
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The vertex to be removed is determined by a decimation module, which has
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to be derived from OpenMesh::Decimater::ModBaseT. The framework
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supplies already a few decimation modules. But it's very easy to build
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your own (\ref OpenMesh::Decimater::ModBaseT). The most important
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function of a decimation module is
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OpenMesh::Decimater::ModBaseT::collapse_priority(). It takes an
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OpenMesh::Decimater::CollapseInfoT describing a potential halfedge
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collapse, and returns a value due to some error metric. The error
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value is used by the decimater to feed a priority queue. Collapses
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with low error will be executed first, and those with large error
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later. Of course a module computing the error quadric is provided
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(OpenMesh::Decimater::ModQuadricT).
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This framework allows to use more than one decimation module with
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some restrictions. Since the error value is always normalized and
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sometimes very difficult to compare to other metrics, the framework
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allows only one non-binary module, i.e. a module computing a float
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value. Every further module must be a binary module,
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i.e. collapse_prioerity() returns
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OpenMesh::Decimater::ModBaseT::LEGAL_COLLAPSE or
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OpenMesh::Decimater::ModBaseT::ILLEGAL_COLLAPSE. In the algorithm
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the binary modules are evaluated first. If the evaluated collapse
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passes the test, then the non-binary module contributes to the
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decision step.
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In some cases the module does not contribute anything to the
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decision engine of the decimater, but instead, e.g. simply collects
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information, while the decimater does it's work. For instance the
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module OpenMesh::Decimater::ModProgMeshT collects information from
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all collapses that have been done. This information can be used to
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generate progressive meshes as described in "Progressive meshes",
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Hoppe, 1996.
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Provided decimation modules:
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- OpenMesh::Decimater::ModQuadricT
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- OpenMesh::Decimater::ModRoundnessT
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- OpenMesh::Decimater::ModNormalFlippingT
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- OpenMesh::Decimater::ModIndependentSetsT
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- OpenMesh::Decimater::ModProgMeshT
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\section DecimaterHnd Module Handles
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Similar to properties the modules are represented outside the
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decimater by module handles. Before using the decimater a
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non-binary module must be registrated with the decimater.
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See \ref DecimaterExa.
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\section DecimaterExa Basic Setup
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The following small example show the basic steps to setup up a
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decimater:
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\include decimater.cc
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*/
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