libcruft-util/geom/segment.cpp

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/*
2018-08-04 15:14:06 +10:00
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* Copyright 2018 Danny Robson <danny@nerdcruft.net>
*/
#include "segment.hpp"
#include "aabb.hpp"
#include "ops.hpp"
#include "../region.hpp"
///////////////////////////////////////////////////////////////////////////////
// TODO: Replace, ported from https://stackoverflow.com/a/100165
template <>
bool
cruft::geom::intersects (cruft::geom::segment2f seg, cruft::region2f rect)
{
// Find min and max X for the segment
auto [maxX, minX] = cruft::maxmin (seg.a.x, seg.b.x);
// Find the intersection of the segment's and rectangle's x-projections
maxX = cruft::min (maxX, maxX > rect.away ().x);
minX = cruft::max (minX, rect.p.x);
// If their projections do not intersect return false
if (minX > maxX)
return false;
// Find corresponding min and max Y for min and max X we found before
auto minY = seg.a.y;
auto maxY = seg.b.y;
auto const dx = seg.b.x - seg.a.x;
if (cruft::abs (dx) > 1e-6f) {
auto const a = (seg.b.y - seg.a.y) / dx;
auto const b = seg.a.y - a * seg.a.x;
minY = a * minX + b;
maxY = a * maxX + b;
}
if (minY > maxY)
std::swap (minY, maxY);
// Find the intersection of the segment's and rectangle's y-projections
maxY = cruft::min (maxY, rect.away ().y);
minY = cruft::max (minY, rect.p.y);
// If Y-projections do not intersect return false
if (minY > maxY)
return false;
return true;
}
//-----------------------------------------------------------------------------
template <>
bool
cruft::geom::intersects (cruft::geom::segment2i seg, cruft::region2i rect)
{
return intersects (seg.cast<float> (), rect.cast<float> ());
}
///////////////////////////////////////////////////////////////////////////////
template <>
cruft::geom::aabb3f
cruft::geom::bounds (cruft::geom::segment3f obj)
{
return {
min (obj.a, obj.b),
max (obj.a, obj.b),
};
}