How ot specify null to a glsl struct member? - glsl

Question

Here is my code
struct Ray {
vec3 origin;
vec3 direction;
bool hit;
Sphere object;
float t;
};
struct Sphere {
vec3 origin;
float radius;
BasicMaterial material;
};
Now, when I create a Ray,my goal is that the object be NULL.
Ray r;
r. origin = origin;
r.direction = dir;
r.hit = false;
r.object = NULL;
r.t = FLT_MAX;
When I run it, I get
error C1503: undefined variable "NULL"
One way I could think of is make a dummy object and initialise with that every time. Is there any better way to do it?

Answer 1

Something like NULL doesn't exist in GLSL. See the most recent OpenGL Shading Language 4.60 Specification (HTML).
Sphere object is not an object reference. The type of object is the structure Sphere. When you assign a variable (s) of type Sphere to object
Sphere s;
Ray r;
r.object = s;
all the elements of s are copied to r.object. GLSL has no concept of objects, object references, inheritance or polymorphism.
Hence the element Sphere object in the structure Ray doesn't make sense. In GLSL you would need to write a function that calculates the intersection of a Ray and a Sphere:
struct Ray
{
vec3 origin;
vec3 direction;
};
struct Sphere
{
vec3 origin;
float radius;
BasicMaterial material;
};
bool IntersectRaySphere(in Ray r, in Sphere s, out float t)
{
// [...]
}