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/*
* Copyright (C) 2024 Jani Hautakangas <jani@kodegood.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "FloatPolygon3D.h"
#include "FloatPlane3D.h"
#include "FloatRect.h"
#include <wtf/TZoneMallocInlines.h>
namespace WebCore {
WTF_MAKE_TZONE_ALLOCATED_IMPL(FloatPolygon3D);
FloatPolygon3D::FloatPolygon3D(const FloatRect& rect, const TransformationMatrix& transform)
{
m_vertices.append(transform.mapPoint(FloatPoint3D(rect.minXMinYCorner())));
m_vertices.append(transform.mapPoint(FloatPoint3D(rect.maxXMinYCorner())));
m_vertices.append(transform.mapPoint(FloatPoint3D(rect.maxXMaxYCorner())));
m_vertices.append(transform.mapPoint(FloatPoint3D(rect.minXMaxYCorner())));
if (auto inverse = transform.inverse())
m_normal = inverse->transpose().mapPoint(m_normal);
else {
FloatPoint3D edge1(m_vertices[1].x() - m_vertices[0].x(), m_vertices[1].y() - m_vertices[0].y(), m_vertices[1].z() - m_vertices[0].z());
FloatPoint3D edge2(m_vertices[2].x() - m_vertices[0].x(), m_vertices[2].y() - m_vertices[0].y(), m_vertices[2].z() - m_vertices[0].z());
m_normal = edge1.cross(edge2);
}
m_normal.normalize();
}
FloatPolygon3D::FloatPolygon3D(Vector<FloatPoint3D>&& vertices, const FloatPoint3D& normal)
: m_vertices(WTFMove(vertices))
, m_normal(normal)
{
}
// Splits the polygon into two parts relative to the given plane.
// Algorithm:
// - For each edge of the polygon:
// - Compute the signed distances of the edge's vertices from the plane.
// - If both vertices are on the same side of the plane, add the starting vertex to the corresponding side's list.
// - If the edge crosses the plane, compute the intersection point:
// - t = di / (di - dj)
// - intersectionPoint = vi + t * (vj - vi)
// - Add the starting vertex and the intersection point to the appropriate lists.
// - Construct two new polygons from the collected vertices.
std::pair<FloatPolygon3D, FloatPolygon3D> FloatPolygon3D::split(const FloatPlane3D& plane) const
{
Vector<FloatPoint3D> positiveVertices;
Vector<FloatPoint3D> negativeVertices;
const float epsilon = std::numeric_limits<float>::epsilon(); // Tolerance for floating point comparisons
unsigned numberOfVertices = m_vertices.size();
for (unsigned i = 0; i < numberOfVertices; ++i) {
const FloatPoint3D& vi = m_vertices[i];
const FloatPoint3D& vj = m_vertices[(i + 1) % numberOfVertices];
float di = plane.distanceToPoint(vi);
float dj = plane.distanceToPoint(vj);
bool viPos = di > epsilon;
bool viNeg = di < -epsilon;
if (viPos) {
positiveVertices.append(vi);
if (dj < -epsilon) {
// Edge crosses from positive to negative
float t = di / (di - dj);
FloatPoint3D intersectionPoint = vi + (vj - vi) * t;
positiveVertices.append(intersectionPoint);
negativeVertices.append(intersectionPoint);
}
} else if (viNeg) {
negativeVertices.append(vi);
if (dj > epsilon) {
// Edge crosses from negative to positive
float t = di / (di - dj);
FloatPoint3D intersectionPoint = vi + (vj - vi) * t;
negativeVertices.append(intersectionPoint);
positiveVertices.append(intersectionPoint);
}
} else { // vi is approximately on the plane
positiveVertices.append(vi);
negativeVertices.append(vi);
}
}
// Create new polygons for each side
return { { WTFMove(negativeVertices), m_normal }, { WTFMove(positiveVertices), m_normal } };
}
} // namespace WebCore
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