public BBTreeBox (MeshNode node) {
this.node = node;
var first = node.GetVertex(0);
var min = new Int2(first.x,first.z);
Int2 max = min;
for (int i=1;i<node.GetVertexCount();i++) {
var p = node.GetVertex(i);
min.x = Math.Min (min.x,p.x);
min.y = Math.Min (min.y,p.z);
max.x = Math.Max (max.x,p.x);
max.y = Math.Max (max.y,p.z);
}
rect = new IntRect (min.x,min.y,max.x,max.y);
left = right = -1;
}