Lon van Ettinger

One of the biggest struggles I faced when implementing the GPU based particles was that I had to learn Vulkan, a modern graphics API. Before this project I only had some experience with OpenGL and the PS5 graphics API. By far the hardest things to set up for the particles were the buffers and all the descriptor sets and layouts. I eventually managed to set-up everything I needed for the particle system by reverse engineering existing graphics passes in our engine while reading up on Vulkan/modern graphics API concepts in several tutorials (mostly at vulkan-tutorial.com).

Another hurdle I encountered about 3 months in, was that I lost the original vision for our particles both visual wise, customizability wise and behavior wise. This was also due to being in my own bubble for those 3 months being the sole person working only on the particle system. At that point, most of the basic functionality for the particle system was in and I had started to make some basic tooling allowing for customization of particles in editor.
To take a step back and get a better view of the state of the system and what was still needed, I sat down together with another team member to try and create various particle effects (e.g. environmental fire/dust and particles when shooting the gun). This helped greatly with identifying missing functionality and/or customizability for the particles.

It's utilizing 3 compute passes and a rendering pass separate from our uber render pass.

(TODO: add diagram and code snippets/links)

Further behavior, like more complex movement and more customizability, is still being tested and in progress.

The logic for spawning emitters is still handled on the CPU using the ECS. Emitters are components and can be spawned on an entity, with parameters from an EmitterPreset, and take the velocity/position of other components of that entity, including from a Jolt rigid body. The SpawnEmitter function used to spawn emitters with is also already integrated into our scripting using wren. The current workflow of spawning an emitter to it landing on the GPU is as shown in the diagram below.

The EmitterPresets are also editable in engine. This still is very much in progress and only has a primitive version implemented, which has already been used to iterate on some particle demos, including one made by a teammate of mine.

As of now 121.000 particles take about 3.396ms on PC. The only major bottleneck I've recognized so far is the rendering of the particles, in this case taking about 3.148ms. Optimizing this is still on our backlog, but since it doesn't impact us as of yet and there's bigger bottlenecks to be handled, it hasn't been prioritized.