magnum/src/MeshTools/RemoveDuplicates.h

#ifndef Magnum_MeshTools_RemoveDuplicates_h
#define Magnum_MeshTools_RemoveDuplicates_h
/*
    This file is part of Magnum.

    Copyright © 2010, 2011, 2012, 2013 Vladimír Vondruš <mosra@centrum.cz>

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/

/** @file
 * @brief Function Magnum::MeshTools::removeDuplicates()
 */

#include <limits>
#include <unordered_map>
#include <vector>
#include <Utility/MurmurHash2.h>

#include "Math/Functions.h"
#include "Magnum.h"

namespace Magnum { namespace MeshTools {

namespace Implementation {

template<class Vertex, std::size_t vertexSize = Vertex::Size> class RemoveDuplicates {
    public:
        RemoveDuplicates(std::vector<UnsignedInt>& indices, std::vector<Vertex>& vertices): indices(indices), vertices(vertices) {}

        void operator()(typename Vertex::Type epsilon = Math::TypeTraits<typename Vertex::Type>::epsilon());

    private:
        class IndexHash {
            public:
                std::size_t operator()(const Math::Vector<vertexSize, std::size_t>& data) const {
                    return *reinterpret_cast<const std::size_t*>(Utility::MurmurHash2()(reinterpret_cast<const char*>(&data), sizeof(data)).byteArray());
                }
        };

        struct HashedVertex {
            UnsignedInt oldIndex, newIndex;

            HashedVertex(UnsignedInt oldIndex, UnsignedInt newIndex): oldIndex(oldIndex), newIndex(newIndex) {}
        };

        std::vector<UnsignedInt>& indices;
        std::vector<Vertex>& vertices;
};

}

/**
@brief %Remove duplicate vertices from the mesh
@tparam Vertex          Vertex data type
@tparam vertexSize      How many initial vertex fields are important (for
    example, when dealing with perspective in 3D space, only first three
    fields of otherwise 4D vertex are important)
@param[in,out] indices  Index array to operate on
@param[in,out] vertices Vertex array to operate on
@param[in] epsilon      Epsilon value, vertices nearer than this distance will
    be melt together.

Removes duplicate vertices from the mesh.

@todo Different (no cycle) implementation for integral vertices
@todo Interpolate vertices, not collapse them to first in the cell
@todo Ability to specify other attributes for interpolation
*/
template<class Vertex, std::size_t vertexSize = Vertex::Size> inline void removeDuplicates(std::vector<UnsignedInt>& indices, std::vector<Vertex>& vertices, typename Vertex::Type epsilon = Math::TypeTraits<typename Vertex::Type>::epsilon()) {
    Implementation::RemoveDuplicates<Vertex, vertexSize>(indices, vertices)(epsilon);
}

namespace Implementation {

template<class Vertex, std::size_t vertexSize> void RemoveDuplicates<Vertex, vertexSize>::operator()(typename Vertex::Type epsilon) {
    if(indices.empty()) return;

    /* Get mesh bounds */
    Vertex min = vertices[0], max = vertices[0];
    for(const auto& v: vertices) {
        min = Math::min(v, min);
        max = Math::max(v, max);
    }

    /* Make epsilon so large that std::size_t can index all vertices inside
       mesh bounds. */
    epsilon = Math::max(epsilon, static_cast<typename Vertex::Type>((max-min).max()/std::numeric_limits<std::size_t>::max()));

    /* First go with original vertex coordinates, then move them by
       epsilon/2 in each direction. */
    Vertex moved;
    for(std::size_t moving = 0; moving <= vertexSize; ++moving) {

        /* Under each index is pointer to face which contains given vertex
           and index of vertex in the face. */
        std::unordered_map<Math::Vector<vertexSize, std::size_t>, HashedVertex, IndexHash> table;

        /* Reserve space for all vertices */
        table.reserve(vertices.size());

        /* Go through all faces' vertices */
        for(auto it = indices.begin(); it != indices.end(); ++it) {
            /* Index of a vertex in vertexSize-dimensional table */
            std::size_t index[vertexSize];
            for(std::size_t ii = 0; ii != vertexSize; ++ii)
                index[ii] = (vertices[*it][ii]+moved[ii]-min[ii])/epsilon;

            /* Try inserting the vertex into table, if it already
               exists, change vertex pointer of the face to already
               existing vertex */
            HashedVertex v(*it, table.size());
            auto result = table.insert(std::pair<Math::Vector<vertexSize, std::size_t>, HashedVertex>(Math::Vector<vertexSize, std::size_t>::from(index), v));
            *it = result.first->second.newIndex;
        }

        /* Shrink vertices array */
        std::vector<Vertex> newVertices(table.size());
        for(auto it = table.cbegin(); it != table.cend(); ++it)
            newVertices[it->second.newIndex] = vertices[it->second.oldIndex];
        std::swap(newVertices, vertices);

        /* Move vertex coordinates by epsilon/2 in next direction */
        if(moving != Vertex::Size) {
            moved = Vertex();
            moved[moving] = epsilon/2;
        }
    }
}

}

}}

#endif