create.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_ALGORITHMS_CORE_CREATE_H
#define VCL_ALGORITHMS_CORE_CREATE_H
 
#include "polygon/create.h"
 
namespace vcl {
 
template<typename ScalarType = float, std::integral UintType = uint16_t>
std::pair<std::vector<vcl::Point3<ScalarType>>, std::vector<UintType>>
createTrackBall(ScalarType scale = 1.0, uint pointsPerCircle = 64)
{
    using PointType = vcl::Point3<ScalarType>;
 
    std::vector<PointType> vertices;
    std::vector<UintType>  edges;
 
    vcl::Polygon2<ScalarType> circle =
        vcl::createCircle<vcl::Polygon2<ScalarType>>(pointsPerCircle, 1.0);
 
    vertices.reserve(pointsPerCircle * 3);
 
    // x
    uint first = 0;
    for (uint i = 0; i < circle.size(); ++i) {
        const auto& p = circle.point(i);
        vertices.push_back(PointType(0, p.x(), p.y()));
        edges.push_back(i + first);
        edges.push_back((i + 1) % circle.size() + first);
    }
 
    // y
    first = circle.size();
    for (uint i = 0; i < circle.size(); ++i) {
        const auto& p = circle.point(i);
        vertices.push_back(PointType(p.x(), 0, p.y()));
        edges.push_back(i + first);
        edges.push_back((i + 1) % circle.size() + first);
    }
 
    // z
    first = 2 * circle.size();
    for (uint i = 0; i < circle.size(); ++i) {
        const auto& p = circle.point(i);
        vertices.push_back(PointType(p.x(), p.y(), 0));
        edges.push_back(i + first);
        edges.push_back((i + 1) % circle.size() + first);
    }
 
    return std::make_pair(std::move(vertices), std::move(edges));
}
 
} // namespace vcl
 
#endif // VCL_ALGORITHMS_CORE_CREATE_H