91 lines
2.6 KiB
C++
91 lines
2.6 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2019 Danny Robson <danny@nerdcruft.net>
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*/
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#pragma once
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#include "fwd.hpp"
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#include "../../extent.hpp"
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#include "../../region.hpp"
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namespace cruft::geom::sample {
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template <typename T>
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struct edge<cruft::extent2<T>> {
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using shape_type = cruft::extent2<T>;
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edge (shape_type _shape)
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: m_shape (_shape)
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{ ; }
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template <typename GeneratorT>
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point2<T>
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eval (GeneratorT &&gen)
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{
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// Generate a point at some point along the perimeter.
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//
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// Unwind half the perimeter with length `w + h - 1`.
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// This gives us the full length of the width, and subtract one of
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// the extreme axis on the height side that is covered by the full
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// width case.
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//
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// If we're in the first portion of the perimeter then choose if
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// we're on the top/bottom randomly. And use the position as the x
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// coordinate.
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//
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// Otherwise bump the coordinate above the baseline which was
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// already covered and choose the left/right side randomly.
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//
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// TODO: avoid repeated calls into uniform. We can do this by
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// doubling the extent we're testing and using the extra bit for
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// the side test. But I'm lacking time right now.
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auto const [w, h] = m_shape;
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auto const len = w + h - 1;
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auto pos = cruft::random::uniform (T{0}, len, gen);
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if (pos <= w) {
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auto const _w = pos;
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auto const _h = cruft::random::uniform (1, gen) ? h : 0;
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return { _w, _h };
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}
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pos -= w;
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auto const _w = cruft::random::uniform (1, gen) ? w : 0;
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auto const _h = pos;
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return { _w, _h };
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}
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private:
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shape_type m_shape;
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};
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template <typename T>
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struct edge<cruft::region2<T>> {
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using shape_type = cruft::region2<T>;
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edge (shape_type _shape)
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: m_shape (_shape)
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{ ; }
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template <typename GeneratorT>
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decltype(auto)
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eval (GeneratorT &&gen)
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{
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return edge<cruft::extent2i> (m_shape.e).eval (
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std::forward<GeneratorT> (gen)
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) + m_shape.p.template as<vector> ();
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}
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private:
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shape_type m_shape;
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};
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}
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