// Tests if the proposed line a intersects with any given line in the level, b
public bool IntersectsNothing(Line a)
{
foreach (Line b in GetAllEdges())
{
if (a.Intersect(b))
{
return(false);
}
}
return(true);
}
// Counts the number of times an infinite line drawn between the point on the line given and some point
// outside the polygon intersects the boundaries of the polygon.
public int NumIntersects(Line line, VertexGraph vg)
{
int count = 0;
bool skip = false;
int ind;
// Creates the "infinite" line, from a point on the drawn line to somewhere outside the polygon
Line infLine = new Line(new Vector2(((line.a.val.x + line.b.val.x) / 2), ((line.a.val.y + line.b.val.y) / 2)), new Vector2(vg.maximumX() + 1, vg.maximumY() + 1));
Line [] edges = vg.GetBoundEdges();
foreach (Line bound in edges)
{
// If the infline intersects with the bound edge, increment counter.
// However, we want to skip the count if:
// This is the second of two edges which connect at a vertex the infline intersects
// (going from inside the shape to outside or vice versa)
// Both lines if its at a vertex where both lines are on the same side of the infline.
//( staying either inside or outside of the shape)
// So to generalize:
// Theres no skip business at all if it's not intersecting a vertex.
// If it is intersecting a vertex, then check if the lines fall on the same side of the line.
// If they are, skip both this and the next line.
// If they're not, skip only this one and not the next.
if (Array.IndexOf(edges, bound) + 1 == edges.Length - 1)
{
ind = Array.IndexOf(edges, bound) + 1;
}
else
{
ind = 0;
}
int otherPoint1; int otherPoint2;
if (Vertex.Orientation(infLine.a, infLine.b, bound.a) == 0)
{
otherPoint1 = Vertex.Orientation(infLine.a, infLine.b, bound.b);
}
else
{
otherPoint1 = Vertex.Orientation(infLine.a, infLine.b, bound.a);
}
if (Vertex.Orientation(infLine.a, infLine.b, edges[ind].a) == 0)
{
otherPoint2 = Vertex.Orientation(infLine.a, infLine.b, edges[ind].b);
}
else
{
otherPoint2 = Vertex.Orientation(infLine.a, infLine.b, edges[ind].a);
}
// This part is tricky.
// Check if the lines are on the same side or opposite sides of the infLine.
// Opposite sides: dont skip this one, but do skip the next.
// Same side: skip both this and the next.
// Therefore, either way, we're skipping the next one. However, if they're on the same side, count++ right now.
if (skip)
{
continue;
}
if (infLine.Intersect(bound))
{
if (infLine.onInfLine(bound))
{
if (otherPoint1 != otherPoint2)
{
count++;
}
skip = true;
}
else
{
count++;
}
}
}
return(count);
}
