bool SHAPE_LINE_CHAIN::PointInside( const VECTOR2I& aPt, int aAccuracy ) const
{
BOX2I bbox = BBox();
bbox.Inflate( aAccuracy );
if( !m_closed || PointCount() < 3 || !BBox().Contains( aPt ) )
return false;
bool inside = false;
/**
* To check for interior points, we draw a line in the positive x direction from
* the point. If it intersects an even number of segments, the point is outside the
* line chain (it had to first enter and then exit). Otherwise, it is inside the chain.
*
* Note: slope might be denormal here in the case of a horizontal line but we require our
* y to move from above to below the point (or vice versa)
*/
for( int i = 0; i < PointCount(); i++ )
{
const auto p1 = CPoint( i );
const auto p2 = CPoint( i + 1 ); // CPoint wraps, so ignore counts
const auto diff = p2 - p1;
if( diff.y != 0 )
{
const int d = rescale( diff.x, ( aPt.y - p1.y ), diff.y );
if( ( ( p1.y > aPt.y ) != ( p2.y > aPt.y ) ) && ( aPt.x - p1.x < d ) )
inside = !inside;
}
}
return inside && !PointOnEdge( aPt, aAccuracy );
}
int PointInPolygon(int n, Point p[]) {
int i, area = 0;
for (i = 0; i < n; ++i) {
//area += p[(i+1) % n].y * (p[i].x - p[(i+2) % n].x); // 如果将式子展开，可以简化成这个样子，减小运算量
area += p[i].x * p[(i+1)%n].y - p[i].y * p[(i+1) % n].x;
}
return (abs(area) - PointOnEdge(n, p)) / 2 + 1;
}
float3 Polygon::RandomPointOnEdge(LCG &rng) const
{
return PointOnEdge(rng.Float());
}
vec AABB::RandomPointOnEdge(LCG &rng) const
{
int i = rng.Int(0, 11);
float f = rng.Float();
return PointOnEdge(i, f);
}
float3 OBB::RandomPointOnEdge(LCG &rng) const
{
return PointOnEdge(rng.Int(0, 11), rng.Float());
}
