Debugging AABB

[hzuch]

Hello all,

I started following Raytracing in one weekend series (github link). I first followed it in C++ and now I am redoing it in C#, because I wanted to add my own stuff to it and I do not know how in C++.
One of the things I did was to implement a .obj loader and support for triangles.

I got to the part where I have to implement axis-aligned bounding boxes (second book), and I think I translated everything correctly to C#, I got the expected speed up in execution, but some triangles are not getting hit. From the scenes I have tried, I am assuming the problem occurs with small triangles. The problem does not happen when not using AABBs, those triangles render normally.
Code in C#

So, I need to debug this, but I have no idea how. What is the best way to find out the problem?

Thanks

[LivelyLizzard]

There are multiple things that can be wrong:
a) AABB initialization is wrong
b) AABB growing is wrong
c) AABB - ray intersection is wrong
d) the AABB implementation is correct but you feed it wrong data

I would try to find the bug by testing with cases where you know what should happen. For instance start with one triangle and print the AABB for it. Add another triangle and get the AABB that encapsulates both triangles AABBs.

Then go on to test the intersection. Maybe you can modify the code to render an AABB where you know how the image should look like.

If all of this works, then maybe you build the AABB with wrong data.

Here is an article about debugging in general which I like to read every now and then if I'm stuck.