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Fix a couple of bugs in 2dConvex Hull algorithm.

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* Need to use atan2 so 3d angles are calculated properly after projection.
* Need to handle case where the first tripple of points is non-convex,
previously this would cause the algorithm to fail with only 1 point.
This commit is contained in:
emMichael Alexander Ewert/em
2014-12-12 15:39:16 -08:00
parent 0ce687853d
commit 92dabdc07d
1 changed files with 16 additions and 3 deletions
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19
src/LinearMath/btGrahamScan2dConvexHull.h
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@@ -85,9 +85,17 @@ inline void GrahamScanConvexHull2D(btAlignedObjectArray<GrahamVector3>& original
originalPoints[0].m_angle = -1e30f;
for (int i=1;i<originalPoints.size();i++)
{
btVector3 xvec = axis0;
btVector3 ar = originalPoints[i]-originalPoints[0];
originalPoints[i].m_angle = btCross(xvec, ar).dot(normalAxis) / ar.length();
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
@@ -111,6 +119,11 @@ inline void GrahamScanConvexHull2D(btAlignedObjectArray<GrahamVector3>& original
else
hull.push_back(originalPoints[i]);
}
if( hull.size() == 1 )
{
hull.push_back( originalPoints[i] );
}
}
}