src/invert.cpp

/*
 *  LDForge: LDraw parts authoring CAD
 *  Copyright (C) 2013 - 2020 Teemu Piippo
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  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
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "src/basics.h"
#include "src/model.h"
#include "src/gl/common.h"
#include "src/invert.h"
#include "src/documentmanager.h"

/*
 * Returns a matrix that causes a flip on the given dimension.
 */
glm::mat4 math::flipmatrix(const Axis dimension)
{
	glm::mat4 result = glm::mat4();
	const int k = static_cast<int>(dimension);
	result[k][k] = -1;
	return result;
}

/*
 * Inverts the winding of a polygon.
 */
void gl::invert(PolygonElement& polygon)
{
	visitPolygon<void>(
		[](LineSegment&) {},
		[](Triangle& tri) {
			std::swap(tri.p1, tri.p2);
		},
		[](Quadrilateral& quad) {
			std::swap(quad.p1, quad.p3);
		},
		[](ConditionalEdge&) {},
		polygon);
}