public void Init(float t_min, float t_max)
{
if (hitable_list.Count > 0)
{
root = new BVH_Node(hitable_list, 0, hitable_list.Count - 1, t_min, t_max);
}
}
public BVH_Node(List <Hitable> nodes, int start_index, int end_index, float t_min, float t_max)
{
//这里就不做nodes为null或者长度为0的考虑了,放到外面去做
//参考raytracingnextweek的方法.每次随机选轴然后排序,然后平分两部分.不断二分直到只剩下1-2个节点.
int node_num = end_index - start_index + 1;
if (node_num == 1)
{
left_node = nodes[start_index];
right_node = null;//书的话是跟left一样.其实如果是这样的话,hit和构造包围盒都需要再判断.看个人喜欢吧
}
else if (node_num == 2)
{
left_node = nodes[start_index];
right_node = nodes[end_index];
}
else
{
switch ((int)utils.GenerateRandomNum(0, 3))
{
case 0:
case 1:
nodes.Sort(start_index, node_num, new CompareInAxisX());
break;
case 2:
nodes.Sort(start_index, node_num, new CompareInAxisY());
break;
case 3:
nodes.Sort(start_index, node_num, new CompareInAxisZ());
break;
}
int mid = (start_index + end_index) / 2;//下面递归不会报错的,因为入口的时候就已经判断好了
left_node = new BVH_Node(nodes, start_index, mid, t_min, t_max);
right_node = new BVH_Node(nodes, mid + 1, end_index, t_min, t_max);
}
AABB left = null;
AABB right = null;
if (left_node != null)
{
left_node.GetBoundingBox(t_min, t_max, ref left);
}
if (right_node != null)
{
right_node.GetBoundingBox(t_min, t_max, ref right);
}
if (left != null && right != null)
{
aabb = AABB.GetSurroundingBox(left, right);
}
else
{
aabb = left != null ? left : right;
}
}