public static Polygon ToPolygon(this Plane plane, Side side)
{
Vector n;
switch (plane.Normal.MaxAxis())
{
case 0:
case 1:
n = Vector.UnitZ;
break;
case 2:
n = Vector.UnitX;
break;
default:
throw new Exception();
}
// project n onto p.Normal, then subtract that from the normal, giving the first base vector of the plane
Debug.Assert(Math.Abs(plane.Normal.LengthSquared - 1) < 1e-8);
var a = (n - n.Dot(plane.Normal) * plane.Normal).Normalized * 16384;
// form the second base vector
var b = a.Cross(plane.Normal);
var origin = plane.Normal * -plane.D;
var polygon = new Polygon();
polygon.Add(new Vertex(origin - b + a, Vector2.Zero, 1));
polygon.Add(new Vertex(origin + b + a, Vector2.Zero, 1));
polygon.Add(new Vertex(origin + b - a, Vector2.Zero, 1));
polygon.Add(new Vertex(origin - b - a, Vector2.Zero, 1));
Debug.Assert(polygon.Vertices.Co.All(_ => Math.Abs(plane.DistanceTo(_)) < 1e-3));
for (var i = 0; i < 4; i++)
{
polygon.Vertices.UV[i] = side.CalcUV(polygon.Vertices.Co[i], side.Material?.BaseTextureTransform);
}
polygon.Vertices.NormalizeUV();
return(polygon);
}
