My julia ray tracer returns StackOverFlowError - julia

Question

I'm trying to write a ray tracer in julia but my main function returns StackOverFlowError. Below is my main function:
function trace(ray::Ray, surfaces::Array{Any, 1}, depth::Int64, maxDepth::Int64)
material, t = findIntersection(ray, surfaces, Inf)
if typeof(material) == Empty
Vec3(0,0,0)
end
if depth > maxDepth
Vec3(0,0,0)
end
if material.isLight == true
material.emittance
end
normal = material.normal
ρ = material.reflectance
BRDF = ρ/3.14159
R = randHemi(normal)
cosθ = dot(R,normal)
newRay = Ray(ray.s + t*ray.d, R)
In = trace(newRay, surfaces, depth+1, maxDepth)
2.0*3.14159*BRDF*In
end
And here is my intersection function:
function findIntersection(ray::Ray, surfaces::Array{Any, 1}, tmin::Float64)
hitSurface = Empty(Vec3(0,0,0), Vec3(0,0,0), Vec3(0,0,0), false)
for surface in surfaces
t = intersect(surface, ray)
if t < tmin
hitSurface = surface
tmin = t
end
end
return hitSurface, tmin
end
But I receive this error:
StackOverflowError:
Stacktrace:
[1] findIntersection(::Ray, ::Array{Any,1}, ::Float64) at .\In[31]:10
[2] trace(::Ray, ::Array{Any,1}, ::Int64, ::Int64) at .\In[33]:2
[3] trace(::Ray, ::Array{Any,1}, ::Int64, ::Int64) at .\In[33]:18 (repeats
14493 times)
[4] top-level scope at In[35]:1
What is the cause of error?

Answer 1

Your problem is that you missed a return.
What you meant to have was
if depth > maxDepth
return Vec3(0,0,0)
end
Without the return, that line just allocates a Vec3, and the code continues looping.

Answer 2

Stackoverflow error usually occurs when there are too many recursive calls. In a nutshell, in most programming languages there is a limit on how many recursive calls you can make.
In your example, the trace functions calls itself recursively and it can cause an stack overflow. You have a parameters maxDepth that can limit that. Setting it to a lower value will probably solve this particular issue.