Ian's Interblog

For fun, I decided to implement my own version of ray tracing in one weekend. It runs on desktop and I also have a webassembly version on this here site (use this one on iOS/Safari or if the other link doesn’t work — some browsers don’t support SharedArrayBuffer). I did a few things different with my version:

• SDL2 Rendering. The book outputs PPM files through stdout, but I realized that I didn’t have a single program that could view PPM files. A quick google search didn’t give me anything very promising. So I just went with outputting directly to the screen with SDL. It was a little bit more upfront work, but it made debugging a lot easier later on.
• Dear IMGUI for the builtin UI. This also makes it a lot easier to test things, since you don’t have to shutdown the program to change various variables and see how it effects the output. I have to say, I’ve always wanted to use IMGUI in a project but never had a chance. It’s now one of my favorite libraries. I know the limitations of Immediate Mode Gui’s, but it’s definitely nice not having to pull in the heft of something like Qt or Gtk.
• GLM for math instead of custom math classes. I just didn’t feel the need to reinvent the wheel here, especially since GLM is very optimized and header-only.
• Multi-threading. C++ has come a long way here, I remember in the past using the OS libraries and having a miserable time. Amazingly, using std::thread and std::atomic I got threading working in a day without any significant bugs. Which, since I never trust threading, I’m sure there’s something lurking in there, but so far everything has been smooth. I haven’t done any optimizations for eliminating false sharing on cache lines or anything like that, but so far the speedup seems to be roughly linear, IE, 12 threads is about 12x faster than one thread.
• Emscripten for web assembly. Fortunately Emscripten has very good SDL2 support, and surprisingly, it can even do multithreading. The only downside with its multithreading is that due to browser security issues, you have to serve up HTTP headers that significantly restrict what’s allowed on the page. So I had to figure out how to modify apache configurations in order to get it online. Overall it wasn’t that hard though.
• CMake for cross platform build support (tested w/ Visual Studio 2022, XCode, web assembly). I have mixed feelings about CMake. On one hand, it’s an incredibly useful tool, and I have no interest in maintaining a lot of separate project files so it’s great in that regard. On the other hand, I absolutely hate the syntax of its custom language. I’m still baffled as to why they couldn’t have just used a scripting language like lua or javascript or python. CMake’s syntax is just weird, things like “else” look like function calls, it’s not clear when you’re supposed to quote things and when you’re not supposed to. It’s also not clear when the order of function calls matters and when it doesn’t, or if they’re function calls or some sort of declaration. I’m reminded of the old Bjarne Stroustrup quote: “There are only two kinds of languages: the ones people complain about and the ones nobody uses.” Replace language with tools and I think it applies to CMake also.

Anyway, in terms of future goals, what I’m planning next for this is:

• glTF mesh/scene support
• Lighting/Emissive materials
• Textures
• PBR materials
• Optimize ray hit detection with something like octrees (haven’t really decided on a data structure yet)
• Maybe a React UI for the web version (although I really like IMGUI even there)

I put more things on here! Which, depending on the quality of said things, is either a gift or a curse. It’s been languishing for a few years, so, I decided I should have more stuff.

Specifically:

• Moved over from Dreamhost to Digital Ocean and switched to a theme made in the last decade. Somehow Dreamhost was taking 8+ seconds to respond, so, this is a lot better.
• An “Art” section, where you can get things like a Font of my handwriting. Exciting!
• A “Tools” section (Note: I have many more that I plan on adding here)
• A “Libraries” section (Same note as the tools section)
• Some Shaders I did for DragonVale back in ye old days
• Various links to horrible game jam games I’m extremely embarrassed by _{oh god just kill me}

Hopefully soon I’ll have more to share on the game I’m working on, along with some more tools and libraries.

This is something I was playing with a few years ago, but I just bumped into it again and I thought it was neat enough to share. The problem I was trying to solve here is how to keep a 3rd person camera from colliding with various and/or having the player occluded, while also keeping it relatively smooth.

The classic way to do this is with a simple ray cast, and, well, that’s certainly an effective strategy. The main problem, from my perspective anyway, is it can lead to abrupt distance changes, and the objects that cause those abrupt changes are by definition out of view (because they’re behind the camera), which makes things feel a bit unpredictable.

Most games solve this by just having good level design, but I thought a more interesting way to do it would be to calculate out a smooth transition. One way to do it would just be to shoot out a lot of rays, but that could get expensive and you still have issues with small colliders possibly being between the gaps. I thought using the depth-buffer might help with this, and indeed it does, so here’s a quick demo of what it looks like. The red texture at the top is a (small) depth buffer that’s looking out from the character’s focal point towards the actual camera; and some layers are used so it only renders certain things (ie, things you don’t want the camera to collide with NPCs and small objects).

I’m using a compute shader to calculate the weighted average to figure out the final camera distance. It works fairly well, although it is admittedly a little more expensive than I’d like. At some point I might add it to the asset store, or just create a download for it.

I wrote a texture generator thing:
https://github.com/fathat/texture-utils

It makes textures like these:

So, uh, if you want fancy checkerboards that might be your jam. Why would you want fancy checkerboards? Well if you’re me, for debugging 3d graphics. If you’re you, I mean, I can’t really tell you.

This is a bit obscure, but recently I’ve been finding myself needing to write some code to answer the question “is this object in an area or not.” Unity3D provides some functionality to do this, but it tends to be a bit imprecise in that only very simple primitives can be used (box collider, sphere collider, convex hull, etc.).

So, in order to automate this a bit, I built some tools to make this a bit easier. You can see/download the result on github.

On the left is the original mesh, on the right is a visualization showing which convex “zones” are created.

What this basically does is takes the selected mesh, and “fills” it with convex colliders marked as triggers. You can then use those triggers however you want.

Some caveats: It’s better to do this with low detail models, as the compiler can take quite a while on larger models. Also while there’s not a hard requirement that the meshes are sealed, the results generally will be better if they are.

Here’s a quick video of the game I’m working on right now. I’ll write some more details up soon.

I’ve been playing with procedural world generation for a while now (because I’m lazy when it comes to level design), which of course means noise functions!

I’m really starting to dig voronoi noise after looking at some of the stuff you can do with it So, I hacked together a voronoi noise previewer:

(Next step: making it actually update in real time. It’s slow!)

Made this goofing around to see if I could compress an entire python program into a single expression. Who said Python Lambda’s aren’t powerful?!

(lambda:
    not globals().__setitem__('sys', __import__('sys'))
    and not globals().__setitem__('this', sys.modules[globals()['__name__']])
    and not globals().__setitem__('time', __import__('time'))
    and
    #program
    [setattr(this, k, v) for k,v in {
            'set_color': (lambda c: w(['*', ' '][c])),
            'abs': (lambda t: (t + (t >> 31)) ^ (t >> 31)),
            'w': sys.stdout.write,
            'smash': (lambda t: -((t * -1) >> 31)),
            'color': (lambda n,k: set_color(smash (k & (n - k)))),
            'col': (lambda n, k: k <= n and not color(n,k) and col(n,k + 1)),
            'row': (lambda n: not w(' ' * (40-abs(n/2)))
                              and (col(abs(n), 0) or True)
                              and not w("\n")
                              and (abs(n) < 63 or n < 0)
                              and not time.sleep(0.05)
                              and row(n+1)),
            'triangle': lambda: row(-60) or True and triangle()
        }.items() ] and triangle() )()

I made this for the reddit game jam about a month ago, but forgot to post it here. So… here it is. It’s pretty short, but for 8 hours it’s surprisingly playable. (I started late)