tri_poly_index_bimap.h

/*****************************************************************************
 * VCLib                                                                     *
 * Visual Computing Library                                                  *
 *                                                                           *
 * Copyright(C) 2021-2025                                                    *
 * Visual Computing Lab                                                      *
 * ISTI - Italian National Research Council                                  *
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 * All rights reserved.                                                      *
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 * This program is free software; you can redistribute it and/or modify      *
 * it under the terms of the Mozilla Public License Version 2.0 as published *
 * by the Mozilla Foundation; either version 2 of the License, or            *
 * (at your option) any later version.                                       *
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 * This program is distributed in the hope that it will be useful,           *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the              *
 * Mozilla Public License Version 2.0                                        *
 * (https://www.mozilla.org/en-US/MPL/2.0/) for more details.                *
 ****************************************************************************/
 
#ifndef VCL_SPACE_COMPLEX_TRI_POLY_INDEX_BIMAP_H
#define VCL_SPACE_COMPLEX_TRI_POLY_INDEX_BIMAP_H
 
#include <vclib/types.h>
 
#include <vector>
 
namespace vcl {
 
class TriPolyIndexBiMap
{
    std::vector<uint> mTriToPoly;
    std::vector<uint> mPolyToTri;
 
public:
    TriPolyIndexBiMap() = default;
 
    uint polygon(uint triangleIndex) const
    {
        assert(triangleIndex < mTriToPoly.size());
        return mTriToPoly[triangleIndex];
    }
 
    uint triangleBegin(uint polygonIndex) const
    {
        assert(polygonIndex < mPolyToTri.size());
        return mPolyToTri[polygonIndex];
    }
 
    uint triangleNumber(uint polygonIndex) const
    {
        // be sure that the current polygon index is valid and the polygon
        // has not been deleted in the mesh
        assert(polygonIndex < mPolyToTri.size());
        assert(mPolyToTri[polygonIndex] != UINT_NULL);
 
        // we need to manage the case in which the polygon was deleted: some
        // values in the mPolyToTri vector could be UINT_NULL. In this case,
        // we just need to jump to the next polygon index having a valid value
 
        // look for the next polygon index having value != UINT_NULL
        uint pnext = polygonIndex + 1;
        while (pnext < mPolyToTri.size() && mPolyToTri[pnext] == UINT_NULL) {
            pnext++;
        }
 
        if (pnext < mPolyToTri.size()) { // there is a next polygon index
            return mPolyToTri[pnext] - mPolyToTri[polygonIndex];
        }
        else {
            // total number of triangles minus the first triangle index of the
            // polygon
            return mTriToPoly.size() - mPolyToTri[polygonIndex];
        }
    }
 
    void clear()
    {
        mTriToPoly.clear();
        mPolyToTri.clear();
    }
 
    void reserve(uint nTriangles, uint nPolygons)
    {
        mTriToPoly.reserve(nTriangles);
        mPolyToTri.reserve(nPolygons);
    }
 
    void insert(uint triangleIndex, uint polygonIndex)
    {
        // add the index of the polygon associated to the triangle
        if (triangleIndex >= mTriToPoly.size()) {
            mTriToPoly.resize(triangleIndex + 1, UINT_NULL);
        }
        mTriToPoly[triangleIndex] = polygonIndex;
 
        // add the index of the triangle associated to the polygon,
        // but only if it is the first triangle index of the polygon!
        if (polygonIndex >= mPolyToTri.size()) {
            mPolyToTri.resize(polygonIndex + 1, UINT_NULL);
        }
        if (mPolyToTri[polygonIndex] == UINT_NULL ||
            triangleIndex < mPolyToTri[polygonIndex])
            mPolyToTri[polygonIndex] = triangleIndex;
    }
 
    uint triangleNumber() const { return mTriToPoly.size(); }
 
    uint polygonNumber() const { return mPolyToTri.size(); }
};
 
} // namespace vcl
 
#endif // VCL_SPACE_COMPLEX_TRI_POLY_INDEX_BIMAP_H