How to unwrap this recursive function into a loop?

Question

I'm writing a simple diffuse path tracer in DirectCompute for education. DirectCompute doesn't allow recursive functions, so I need to figure out how to turn this recursive statement into a loop:

intersectCode() {

    // ... intersection code 

    if(hit an object)
        return objectHit.diffuse * (intersectCode() + objectHit.emittance);
}

Generic pseudo-code or C example would be really appreciated

Answer 1

object = initialObject;
objectStack = new ObjectStack();
do {
    objectStack.push(object);
    // get new intersected object as object

} while (object);

result = 0;
while (object = objectStack.pop()) {
    result = object.diffuse * (result + object.emittance);
}

return result;

You might want to adjust that, because all details are not known - for example, maybe initObject does not have to be in stack?