mirror of https://github.com/axmolengine/axmol.git
130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
/*
|
|
Bullet Continuous Collision Detection and Physics Library
|
|
Copyright (c) 2011 Advanced Micro Devices, Inc. http://bulletphysics.org
|
|
|
|
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.
|
|
*/
|
|
|
|
#ifndef GRAHAM_SCAN_2D_CONVEX_HULL_H
|
|
#define GRAHAM_SCAN_2D_CONVEX_HULL_H
|
|
|
|
#include "btVector3.h"
|
|
#include "btAlignedObjectArray.h"
|
|
|
|
struct GrahamVector3 : public btVector3
|
|
{
|
|
GrahamVector3(const btVector3& org, int orgIndex)
|
|
: btVector3(org),
|
|
m_orgIndex(orgIndex)
|
|
{
|
|
}
|
|
btScalar m_angle;
|
|
int m_orgIndex;
|
|
};
|
|
|
|
struct btAngleCompareFunc
|
|
{
|
|
btVector3 m_anchor;
|
|
btAngleCompareFunc(const btVector3& anchor)
|
|
: m_anchor(anchor)
|
|
{
|
|
}
|
|
bool operator()(const GrahamVector3& a, const GrahamVector3& b) const
|
|
{
|
|
if (a.m_angle != b.m_angle)
|
|
return a.m_angle < b.m_angle;
|
|
else
|
|
{
|
|
btScalar al = (a - m_anchor).length2();
|
|
btScalar bl = (b - m_anchor).length2();
|
|
if (al != bl)
|
|
return al < bl;
|
|
else
|
|
{
|
|
return a.m_orgIndex < b.m_orgIndex;
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
inline void GrahamScanConvexHull2D(btAlignedObjectArray<GrahamVector3>& originalPoints, btAlignedObjectArray<GrahamVector3>& hull, const btVector3& normalAxis)
|
|
{
|
|
btVector3 axis0, axis1;
|
|
btPlaneSpace1(normalAxis, axis0, axis1);
|
|
|
|
if (originalPoints.size() <= 1)
|
|
{
|
|
for (int i = 0; i < originalPoints.size(); i++)
|
|
hull.push_back(originalPoints[0]);
|
|
return;
|
|
}
|
|
//step1 : find anchor point with smallest projection on axis0 and move it to first location
|
|
for (int i = 0; i < originalPoints.size(); i++)
|
|
{
|
|
// const btVector3& left = originalPoints[i];
|
|
// const btVector3& right = originalPoints[0];
|
|
btScalar projL = originalPoints[i].dot(axis0);
|
|
btScalar projR = originalPoints[0].dot(axis0);
|
|
if (projL < projR)
|
|
{
|
|
originalPoints.swap(0, i);
|
|
}
|
|
}
|
|
|
|
//also precompute angles
|
|
originalPoints[0].m_angle = -1e30f;
|
|
for (int i = 1; i < originalPoints.size(); i++)
|
|
{
|
|
btVector3 ar = originalPoints[i] - originalPoints[0];
|
|
btScalar ar1 = axis1.dot(ar);
|
|
btScalar ar0 = axis0.dot(ar);
|
|
if (ar1 * ar1 + ar0 * ar0 < FLT_EPSILON)
|
|
{
|
|
originalPoints[i].m_angle = 0.0f;
|
|
}
|
|
else
|
|
{
|
|
originalPoints[i].m_angle = btAtan2Fast(ar1, ar0);
|
|
}
|
|
}
|
|
|
|
//step 2: sort all points, based on 'angle' with this anchor
|
|
btAngleCompareFunc comp(originalPoints[0]);
|
|
originalPoints.quickSortInternal(comp, 1, originalPoints.size() - 1);
|
|
|
|
int i;
|
|
for (i = 0; i < 2; i++)
|
|
hull.push_back(originalPoints[i]);
|
|
|
|
//step 3: keep all 'convex' points and discard concave points (using back tracking)
|
|
for (; i != originalPoints.size(); i++)
|
|
{
|
|
bool isConvex = false;
|
|
while (!isConvex && hull.size() > 1)
|
|
{
|
|
btVector3& a = hull[hull.size() - 2];
|
|
btVector3& b = hull[hull.size() - 1];
|
|
isConvex = btCross(a - b, a - originalPoints[i]).dot(normalAxis) > 0;
|
|
if (!isConvex)
|
|
hull.pop_back();
|
|
else
|
|
hull.push_back(originalPoints[i]);
|
|
}
|
|
|
|
if (hull.size() == 1)
|
|
{
|
|
hull.push_back(originalPoints[i]);
|
|
}
|
|
}
|
|
}
|
|
|
|
#endif //GRAHAM_SCAN_2D_CONVEX_HULL_H
|