Intermediate

This category contains more advanced articles that build on background knowledge or previous articles.

See Beginner and Advanced for more articles.

Oatmeal Spice

| Boris

Say you’ve written a little procedural generation program. Say it’s some art, music or level generator. It looks kinda cool, but after a few generations, you are already bored with it. Somehow, for all your careful design, all your generated results look samey, boring. This is Kate Compton’s ten-thousand bowl of oatmeal problem: every bowl of oatmeal is unique, but that does not make them interesting or valuable.

What can you do about it? In this article, I want to talk about how we can improve the interestingness of the results, not by adding more content, but by taking things away.

Continue reading →

Infinite Random Rectangles – the Poisson Rect process

| Boris

Previously, we looked at how to sample points randomly at a given density across an infinite plane.

It’s harder than it sounds, as I was looking for an algorithm that was not biased by the size/shape of the chunks used to calculate it.

Today let’s extend that to filling the infinite plane with random non-overlapping rectangles. As before, that means finding a deterministic chunked algorithm that we can prove is unaffected by the choice of chunking.

Continue reading →

More Accelerated Game of Life

| Boris

I got a good comment on my previous article about implementing the Game of Life in CUDA pointing out that I was leaving a lot of performance at the table by only considering a single step at once.

Their point was that my implementations were bound by the speed of DRAM. An A40 can send 696 GB/s from DRAM memory to the cores, and my setup required sending at least one bit in each direction per-cell per-step, which worked out at 1.4ms.

But DRAM is the slowest memory on a graphics card. The L1 cache is hosted inside each Streaming Multiprocessor, much closer to where the calculations can occur. It’s tiny, but has an incredible bandwidth – potentialy 67 TB/s. Fully utilizing this is nigh impossible, but even with mediocre utilization we’d do far better than before.

Continue reading →

Accelerated Game Of Life with CUDA / Triton

| Boris

Let’s look at implementing Conway’s Game of Life using a graphics card. I want to experiment with different libraries and techniques, to see how to get the best performance. I’m going to start simple, and get increasingly complex as we dive in.

The Game Of Life is a simple cellular automata, so should be really amenable to GPU acceleration. The rules are simple: Each cell in the 2d grid is either alive or dead. At each step, count the alive neighbours of the cell (including diagonals). If the cell is alive, it remains alive if 2 or 3 neighbours are alive. Otherwise it dies. If the cell is dead, it comes ot life if exactly 3 neighbours are alive. These simple rules cause an amazing amount of emergent complexity which has been written about copiously elsewhere.

For simplicity, I’ll only consider N×N grids, and skip calculations on the boundary. I ran everything with an A40, and I’ll benchmark performance at N=216 . For now, we’ll store each cell as 1 byte so this array is which equates to 4 GB of data.

All code is shared in the GitHub repo.

Continue reading →

Exploring Rectangle Subdivisions

| Boris

Last week, I saw a talk on Vuntra City, a procedurally generated city with a fully explorable city. Developer Larissa Davidova explained that she settled on using Recursive Subdivision for the city blocks, as she wanted some level of organicness, while still only having to deal with rectangles. But she didn’t like having indefinitely long roads that cause implausible sightlines.

One way Vuntra City handles this is by subdividing a rectangle into 5 blocks, a pattern I called “whirl” in my previous article on recursive subdivision. You can see that it has no internal roads that stretch across the entire map.

But Larissa’s talk got me thinking. The whirl pattern is interesting because it cannot be made from simple cuts. What other ways of subdividing a rectangle into smaller rectangles1, are out there?

Continue reading →

Quantum WaveFunctionCollapse

| Boris

One of my biggest gripes with the WaveFunctionCollapse procedural generation algorithm is that, despite the name, it doesn’t really have anything to do with quantum mechanics. I usually prefer the term Constraint Based Procedural Generation instead.

The name WaveFunctionCollapse is meant more as an analogy. As the algorithm progresses, it resolves a fuzzy, uncertain picture of the output into sharper detail, much as in quantum mechanics, the state of a system is also a range of possibilities, which resolves to something specific when “observed”.

But could we adapt WFC to the Quantum way of thinking, and ran it on actual Quantum Hardware? Well, that’s exactly what is discussed in this new paper Quantum WaveFunctionCollapse by Raoul Heese1 (Youtube summary). Does it work? Is it fast? Let’s find out.

Continue reading →