Fast reciprocal square root... in 1997?! 1 Jun 2021 - i76 This article is part of my series on reverse engineering Interstate ‘76, with my current goal being to add a Vulkan renderer to the game. I’m basing this work directly on UCyborg’s patches which include many much-needed fixups to the game,…

Chandler Caruth (I think - I can't for the life of me find the reference) said something in a cppcon talk years ago that blew my mind. More or less, 95% of code performance comes from the memory layout and memory access patters of data structures, and 5% comes from clever instruction selection and…

I’ve decided to write up a little history of ispc, the compiler I wrote when I was at Intel. There’s a lot to say, so it’ll come out in a series of posts over the next few weeks. While I’ve tried to get all the details right and properly credit people, this is all from my memory. For anyone who was…

After Sweden, I still had my day job at Intel that didn’t involve writing a compiler; I was the tech lead of the advanced rendering group. At the time, I reported to Elliot Garbus, then the VP in charge of graphics software. Elliot was the best manager I’ve ever had. To be honest, I didn’t expect…

Note: in these posts, I’m not going to go into comprehensive detail about how ispc/volta works on a technical level, what the precursors were, or what all of the key design goals were. I’ll touch on some of that as is relevant to the narrative, but see the paper I wrote about ispc with Bill Mark for…

As before, this is from memory. I did my best to get the details right, but get in touch if I got anything wrong. There was a small set of benchmarks that the compiler team used to evaluate parallel programming models—things like Black-Scholes options pricing, evaluating the Mandelbrot set, a little…

One thing that came out of volta’s impressive early results was an invitation to participate a series of parallel programming model bake-offs that were going on in the compiler team. Here’s how it went: every few months, a group would be assembled with a representative or two from each of Intel’s…

Come late 2011, I was pretty excited about the imminent arrival of AVX on Sandybridge CPUs: after years of SSE’s 4-wide vectors (for 32-bit data types), AVX was doubling that, making it possible to do 8-wide 32-bit vector ops instead. This was probably the most exciting thing that had happened in…

It wasn’t quite fair to describe volta as a dumb compiler earlier; we’ll revisit that topic today. Not only were a number of the language features carefully designed to map well to CPU hardware, but a number of custom optimization passes for LLVM IR turned out to be important for keeping performance…

The usual caveat: this is all from memory and it’s been a few years now. If you were around then and see anything I misremembered, please send an email and I’ll happily make corrections. In the Spring of 2011, there was a reorg and most of the graphics software people moved into the hardware…

Growing Pains in Engine Development Aras Pranckevičius is a Lithuanian programmer who has been working on the Unity game engine since 2006. Before that, he worked on some demoscene demos and small gam

So… this is a highly discussed topic these days. Many engines already do Deferred Shading. Doom 2016 decided to go Forward at 60 FPS with 1080p, thus making popular that big AAA titles with high demands can do Forward just fine (although it’s not the first nor only AAA title that uses Forward. Forza…

Background (originally published for Patreon backers November 2016) General background for all these articles… I’m writing about major areas I’ve ignored in the past, using Unity as a convenient demo-environment for the ideas and tests: Multi-threading Querying / filtering Networking Unity…

Did you know that Google Chrome has a built-in profiler? Some people assume it’s only for profiling “web stuff” like JavaScript execution. But it can also be used as a really nice frontend for your own profiling data. Colt McAnlis actually wrote about using it for game profiling, in 2012: Using…

In the previous posting I said it “was a good place to stop for the night”. And I had decided to, but as sometimes happens, I changed my mind and worked for about another 45 minutes until I had solved the problem. I knew I had a problem in at least some DDS files. I checked the old version of Braid…

I’ve changed a lot of files, and because this is a major change expected to break the game somewhat, I’m doing it in a new repository. I’ve been working on my laptop, so the next step is … download the new repository on my desktop machine and make sure everything compiles and runs and can upload a…

AUGUST 3, 2016 Realtime global illumination (part 1) Figure 1: A simple diffuse box scene with a point light. Left: Direct illumination. Middle: Indirect illumination, rendered using this algorithm. Right: Composited result. I recently decided that I needed a simple and efficient global illumination…

AUGUST 21, 2016 Realtime global illumination (part 3) Because I've had little time to work on this lately, I'll try to wrap up as much as I can in this post. First, I'll discuss an improvement to form factor compression, over the results from the previous post. After that, more practical matters for…

AUGUST 11, 2016 Realtime global illumination (part 2) Figure 1: The box scene with global illumination. In the last post, I explained the basics of the global illumination algorithm I have been experimenting with. I was deliberately brief when discussing the calculation and compression of form…

Handmade Penguin Chapter 16: Bits and Pieces This chapter covers roughly the content in the VisualStudio Compiler Switches part of the Handmade Hero course, under the Linux operating system. Don't say I didn't warn you! Be warned! Most of today's chapter deals with gcc. If you're using another…