c++ recursion error
I have the following recursive code and it doesn't behave as expected (see details below):
R3Intersection ComputeIntersectionNode(R3Ray *ray, R3Node *node)
{
R3Intersection closest_inter;
R3Intersection child_inter;
R3Intersection shape_inter;
double least_t = DBL_MAX;
// check for intersection with shape
if(node->shape != NULL)
{
shape_inter = ComputeIntersectionShape(ray, node->shape);
if(shape_inter.hit == 1)
closest_inter = shape_inter;
}
// go through all the children and for each child, compute
// the closest intersection with ray
for(int i = 0; i < node->children.size(); i++)
{
// compute intersection with children[i] and ray
child_inter = ComputeIntersectionNode(ray, node->children[i]);
// if there's an intersection with the child node and
// it is the closest intersection, set closest intersection
if(child_inter.hit == 1 && fabs(child_inter.t) < fabs(least_t))
closest_inter = child_inter;
}
return closest_inter;
}
This ComputeIntersectionNode(...)
, in addition to the recursive calls, is also being called for multiple ra开发者_开发问答ys in the program. To test this function, I run it for 4 rays
and 4 nodes
(or more precisely, one root
of type node
, which doesn't have a shape
, but has 4 children
, each of which have one shape
). For testing, each ray
intersects exactly one node
/shape
.
When I run the code in GDB for the first ray
, it first passes the root
through the code, which doesn't have a shape
, so then it goes directly to the children
. It computes the first child's intersection correctly and sets the closest_inter
variable correctly as well, which gets returned to the highest level of recursion and child_inter
as well as closest_inter
are set here with child_inter.hit = 1;
Then, the second child is processed. ComputeIntersectionShape(...)
returns no intersection with the second child (shape_inter.hit == 0
;) - this is expected behavior. However, when the function returns to the highest level of recursion, for some reason child_inter.hit is set to 1 (but should be set to 0).
Any suggestions?
Thank you in advance.
I think your problem is caused by the fact you are returning a default-initialized R3Intersection
(ie. you don't return the shape_inter
when it doesn't intersect). Depending on its default constructor, you might get what you see.
精彩评论