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/*
** ClanLib SDK
** Copyright (c) 1997-2005 The ClanLib Team
**
** This software is provided 'as-is', without any express or implied
** warranty. In no event will the authors be held liable for any damages
** arising from the use of this software.
**
** Permission is granted to anyone to use this software for any purpose,
** including commercial applications, and to alter it and redistribute it
** freely, subject to the following restrictions:
**
** 1. The origin of this software must not be misrepresented; you must not
** claim that you wrote the original software. If you use this software
** in a product, an acknowledgment in the product documentation would be
** appreciated but is not required.
** 2. Altered source versions must be plainly marked as such, and must not be
** misrepresented as being the original software.
** 3. This notice may not be removed or altered from any source distribution.
**
** Note: Some of the libraries ClanLib may link to may have additional
** requirements or restrictions.
**
** File Author(s):
**
** Magnus Norddahl
** (if your name is missing here, please add it)
*/
#include "Core/precomp.h"
#include <cmath>
#include "API/Core/Math/triangle_math.h"
/*
---- from comp.graphics.algorithms FAQ ----
calculate the barycentric coordinates
for a triangle {(x1,y1), (x2,y2), (x3,y3)} and some point (x0,y0)
Then if b1, b2, and b3 are all > 0, (x0,y0) is strictly inside the triangle;
if bi = 0 and the other two coordinates are positive,
(x0,y0) lies on the edge opposite (xi,yi);
if bi and bj = 0, (x0,y0) lies on (xk,yk); if bi < 0,
(x0,y0) lies outside the edge opposite (xi,yi);
if all three coordinates are negative, something else is wrong.
*/
bool CL_TriangleMath::point_inside_triangle(const CL_Pointf &P, float *vertices, bool on_edge_is_outside)
{
return point_inside_triangle(P.x, P.y, vertices, on_edge_is_outside);
}
bool CL_TriangleMath::point_inside_triangle( float px, float py, float *vertices, bool on_edge_is_outside)
{
const float &tx0 = vertices[0];
const float &ty0 = vertices[1];
const float &tx1 = vertices[2];
const float &ty1 = vertices[3];
const float &tx2 = vertices[4];
const float &ty2 = vertices[5];
float b0 = (tx1 - tx0) * (ty2 - ty0) - (tx2 - tx0) * (ty1 - ty0);
float b1 = ((tx1 - px) * (ty2 - py) - (tx2 - px) * (ty1 - py)) / b0;
float b2 = ((tx2 - px) * (ty0 - py) - (tx0 - px) * (ty2 - py)) / b0;
float b3 = ((tx0 - px) * (ty1 - py) - (tx1 - px) * (ty0 - py)) / b0;
if( (b1 > 0 && b2 > 0 && b3 > 0) ) // strictly inside
{
return true;
}
if( on_edge_is_outside == false ) // on edge?
if( (b1>=0 && b2>=0 && b3>=0) && (b1+b2+b3) >= 0 )
return true;
return false;
}
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