// line intersection helper function: does line segment (p1,p2) intersect segment (p3,p4) ?
public Intersect line_intersect(Vec p1, Vec p2, Vec p3, Vec p4)
{
Intersect result = new Intersect()
{
intersect = false
};
var denom = (p4.y - p3.y) * (p2.x - p1.x) - (p4.x - p3.x) * (p2.y - p1.y);
if (denom == 0.0)
{
result.intersect = false;
} // parallel lines
var ua = ((p4.x - p3.x) * (p1.y - p3.y) - (p4.y - p3.y) * (p1.x - p3.x)) / denom;
var ub = ((p2.x - p1.x) * (p1.y - p3.y) - (p2.y - p1.y) * (p1.x - p3.x)) / denom;
if (ua > 0.0 && ua < 1.0 && ub > 0.0 && ub < 1.0)
{
var up = new Vec(p1.x + ua * (p2.x - p1.x), p1.y + ua * (p2.y - p1.y));
return(new Intersect {
ua = ua, ub = ub, up = up, intersect = true
}); // up is intersection point
}
return(result);
}
//private void util_add_box(List<Wall> lst, double x, double y, double w, double h) {
// lst.Add(new Wall(new Vec(x, y), new Vec(x + w, y)));
// lst.Add(new Wall(new Vec(x + w, y), new Vec(x + w, y + h)));
// lst.Add(new Wall(new Vec(x + w, y + h), new Vec(x, y + h)));
// lst.Add(new Wall(new Vec(x, y + h), new Vec(x, y)));
//}
// helper function to get closest colliding walls/items
public Intersect stuff_collide_(Vec p1, Vec p2, bool check_walls, bool check_items)
{
Intersect minres = new Intersect()
{
intersect = false
};
// collide with walls
if (check_walls)
{
for (int i = 0, n = this.walls.Count; i < n; i++)
{
Wall wall = this.walls[i];
Intersect res = line_intersect(p1, p2, wall.p1, wall.p2);
if (res.intersect)
{
res.type = 0; // 0 is wall
if (!minres.intersect)
{
minres = res;
}
else // check if its closer
{
if (res.ua < minres.ua)
{
// if yes replace it
minres = res;
}
}
}
}
}
// collide with items
//if (check_items) {
// for (int i = 0, n = this.items.Count; i < n; i++) {
// Item it = this.items[i];
// Intersect res = line_point_intersect(p1, p2, it.p, it.rad);
// if (res.intersect) {
// res.type = it.type; // store type of item
// if (!minres.intersect) { minres = res; } else { // check if its closer
// if (res.ua < minres.ua) {
// // if yes replace it
// minres = res;
// }
// }
// }
// }
//}
return(minres);
}
public Intersect line_point_intersect(Vec A, Vec B, Vec C, double rad)
{
Intersect result = new Intersect {
intersect = false
};
var v = new Vec(B.y - A.y, -(B.x - A.x)); // perpendicular vector
var d = Math.Abs((B.x - A.x) * (A.y - C.y) - (A.x - C.x) * (B.y - A.y));
d = d / v.length();
if (d > rad)
{
return(result);
}
v.normalize();
v.scale(d);
double ua = 0.0;
var up = C.add(v);
if (Math.Abs(B.x - A.x) > Math.Abs(B.y - A.y))
{
ua = (up.x - A.x) / (B.x - A.x);
}
else
{
ua = (up.y - A.y) / (B.y - A.y);
}
if (ua > 0.0 && ua < 1.0)
{
result = new Intersect {
ua = ua, up = up, intersect = true
};
}
return(result);
}