Comment by delfinom
9 months ago
Kind of both in my opinion. But rust is bringing nothing to the table that games need.
At best rust fixes crash bugs and not the usual logic and rendering bugs that are far more involved and plague users more often.
9 months ago
Kind of both in my opinion. But rust is bringing nothing to the table that games need.
At best rust fixes crash bugs and not the usual logic and rendering bugs that are far more involved and plague users more often.
The ability of engines like Bevy to automatically schedule dependencies and multithread systems, which relies on Rust's strictness around mutability, is a big advantage. Speaking as someone who's spent a long time looking at Bevy profiles, the increased parallelism really helps.
Of course, you can do job queuing systems in C++ too. But Rust naturally pushes you toward the more parallel path with all your logic. In C++ the temptation is to start sequential to avoid data races; in systems like Bevy, you start parallel to begin with.
Aside from a physics simulation, I'm curious as to what you think would be a positive cost benefit from that level of multithreading for the majority of game engines. Graphical pipelines take advantage of the concept but offload as much work as possible to the GPU.
We were doing threading beyond that in 2010, you could easily have rendering, physics, animation, audio and other subsystems chugging along on different threads. As I was leaving the industry most engines were trending towards very parallel concurrent job execution systems.
The PS3 was also an interesting architecture(i.e. SPUs) from that perspective but it was so distant from the current time that it never really took off. Getting existing things ported to it was a beast.
Bevy really nails the concurrency right IMO(having worked on AA/AAA engines in the past) it's missing a ton in other dimensions but the actual ECS + scheduling APIs are a joy. Last "proper" engine I worked on was a rats-nest of concurrency in comparison.
That said as a few other people pointed out, the key is iteration, hot-reload and other things. Given the choice I'd probably do(and have done) a Rust based engine core where you need performance/stability and some dynamic language on top(Lua, quickjs, etc) for actual game content.
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In big-world high-detail games, the rendering operation wants so much time that the main thread has time for little else. There's physics, there's networking, there's game movement, there's NPC AI - those all need some time. If you can get that time from another CPU, rendering tends to go faster.
I tend to overdo parallelism. Load this file into a Tracy profile, version 0.10.0, and you can see what all the threads in my program are doing.[1] Currently I'm dealing with locking stalls at the WGPU level. If you have application/Rend3/WGPU/Vulkan/GPU parallism, every layer has to get it right.
Why? Because the C++ clients hit a framerate wall, with the main thread at 100% and no way to get faster.
[1] https://animats.com/sl/misc/traces/clockhavenspeed02.tracy
Animations are an example. I landed code in Bevy 0.13 to evaluate all AnimationTargets (in Unity speak, animators) for all objects in parallel. (This can't be done on GPU because animations can affect the transforms of entities, which can cause collisions, etc. triggering arbitrary game logic.) For my test workload with 10,000 skinned meshes, it bumped up the FPS by quite a bit.
"Fearless concurrency"