// Build a BSP tree out of `polygons`. When called on an existing tree, the
// new polygons are filtered down to the bottom of the tree and become new
// nodes there. Each set of polygons is partitioned using the first polygon
// (no heuristic is used to pick a good split).
public void Build(List <CSG_Polygon> list)
{
if (list == null || list.Count < 1)
{
return;
}
if (plane == null || !plane.Valid())
{
plane = new CSG_Plane
{
normal = list[0].plane.normal,
w = list[0].plane.w
};
}
if (polygons == null)
{
polygons = new List <CSG_Polygon>();
}
var listFront = new List <CSG_Polygon>();
var listBack = new List <CSG_Polygon>();
for (int i = 0; i < list.Count; i++)
{
plane.SplitPolygon(list[i], polygons, polygons, ref listFront, ref listBack);
}
if (listFront.Count > 0)
{
if (front == null)
{
front = new CSG_Node();
}
front.Build(listFront);
}
if (listBack.Count > 0)
{
if (back == null)
{
back = new CSG_Node();
}
back.Build(listBack);
}
}
// Return a new CSG solid representing space both this solid and in the
// solid `csg`. Neither this solid nor the solid `csg` are modified.
public static CSG_Node Intersect(CSG_Node a1, CSG_Node b1)
{
CSG_Node a = a1.Clone();
CSG_Node b = b1.Clone();
a.Invert();
b.ClipTo(a);
b.Invert();
a.ClipTo(b);
b.ClipTo(a);
a.Build(b.AllPolygons());
a.Invert();
CSG_Node ret = new CSG_Node(a.AllPolygons());
return(ret);
}