DEVLOG 9 - 100K Entities

 
After the last devlog, in which I rendered 1K entities, I tried increasing the number of entities to a 15x15x15 cube, or 3375 entities, and I saw the frame rate drop unexpectedly, 25 FPS. I was wondering if this was normal or not… Apparently, it wasn’t… I tried to figure out the problem, but it wasn’t easy.
 
I tried using a tool called RenderDoc that lets you see what’s happening on the GPU, so all the calls, data passed to the GPU, buffers, textures, etc. That information also included the time, and the GPU indicated it was taking about 16 ms, which was quite strange.
 
I started to suspect Vulkan’s validation layers. By disabling them, I got to 30 FPS or a little higher, I don’t remember exactly. Then I disabled ASan and set the swapchain to Immediate Mode so as not to be constrained by the screen refresh rate, and I got to about 100 FPS. Then I made several CPU-level optimizations at the code level by changing the way components are obtained from batches in my ECS system, specifically limiting those operations that can be avoided in the internal component iteration loop, and I got up to 140 fps. Finally, the thing that made me open my eyes and say WOW was compiling in Release and not Debug, the fps skyrocketed to around 2300… I couldn’t believe it either…
 
After doing all this, I rendered 100,000 entities and my fps were stable at 90… Incredible! Finally, just for the sake of curiosity, I tested 1,000,000 entities and got 9 fps, which is good because it means the system scales linearly.
 
This is what I’ve been doing for the last two hours. Before that, I spent some time revisiting my ECS code to make it more secure. For example, many of the Table and EntityManager methods now return references and not pointers. I’ve also made the ComponentRegistry class much more efficient by storing component information in contiguous arrays instead of lists, which therefore contain non-contiguous data.
 
Next Steps:
I need to implement a way to get verified IDs from the EntityManager, since currently the IDs are only manual and non-unique. And then I’ll need to refactor the rendering code again, making it more modular, since it’s currently all in a single class.