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Simulating fluids, fire, and smoke in real-time

andrewkchan.dev

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Re: Simulating fluids, fire, and smoke in real-time

#21

Post by bee_rider »

photoGrant wrote: post #15
bee_rider wrote: post #10

They mention simulating fire and smoke for games, and doing fluid simulations on the GPU. Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? It seems like running a CFD problem and rendering at the same time is a lot. Can this stuff run on an iGPU while the dGPU is doing more rendering-related tasks? Or are iGPUs just too weak, better to fall all the way down to the CP…

Welp. It used to be PhysX math would run on a dedicated gpu of choice. I remember assigning or realising this during the Red Faction game with forever destructing walls. Almost Minecraft, but with rocket launchers on mars

I remember PhysX, but my feeling at the time was “yeah I guess NVIDIA would love for me to buy two graphics cards.” On the other hand, processors without any iGPUs are pretty rare by now.

Re: Simulating fluids, fire, and smoke in real-time

#22

Post by teh_infallible »

Valgrim wrote: post #19
bee_rider wrote: post #10

They mention simulating fire and smoke for games, and doing fluid simulations on the GPU. Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? It seems like running a CFD problem and rendering at the same time is a lot. Can this stuff run on an iGPU while the dGPU is doing more rendering-related tasks? Or are iGPUs just too weak, better to fall all the way down to the CP…

Now that LLMs run on GPU too, future GPUs will need to juggle between the graphics, the physics and the AI for NPCs. Fun times trying to balance all that. My guess is that the load will become more and more shared between local and remote computing resources.

Maybe in the future, personal computers will have more than one GPU, one for graphics and one for AI?

Re: Simulating fluids, fire, and smoke in real-time

#24

Post by softfalcon »

bee_rider wrote: post #10

They mention simulating fire and smoke for games, and doing fluid simulations on the GPU. Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? It seems like running a CFD problem and rendering at the same time is a lot. Can this stuff run on an iGPU while the dGPU is doing more rendering-related tasks? Or are iGPUs just too weak, better to fall all the way down to the CP…

> Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy?

Short answer: No, it's not "already busy". GPU's are so powerful now that you can do physics, fancy render passes, fluid sims, "Game AI" unit pathing, and more, at 100+ FPS.

Long answer: You have a "frame budget" which is the amount of time between rendering the super fast "slide show" of frames at 60+ FPS. This gives you between 5 and 30 ms to do a bunch of computation to get the results you need to compute state and render the next frame.

That could be moving units around a map, calculating fire physics, blitting terrain textures, rendering verts with materials. In many game engines, you will see a GPU doing dozens of these separate computations per frame.

GPU's are basically just a secondary computer attached to your main computer. You give it a bunch of jobs to do every frame and it outputs the results. You combine results into something that looks like a game.

> Can this stuff run on an iGPU while the dGPU is doing more rendering-related tasks?

Almost no one is using the iGPU for anything. It's completely ignored because it's usually completely useless compared to your main discrete GPU.

Re: Simulating fluids, fire, and smoke in real-time

#25

Post by bee_rider »

softfalcon wrote: post #24
bee_rider wrote: post #10

They mention simulating fire and smoke for games, and doing fluid simulations on the GPU. Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? It seems like running a CFD problem and rendering at the same time is a lot. Can this stuff run on an iGPU while the dGPU is doing more rendering-related tasks? Or are iGPUs just too weak, better to fall all the way down to the CP…

> Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? Short answer: No, it's not "already busy". GPU's are so powerful now that you can do physics, fancy render passes, fluid sims, "Game AI" unit pathing, and more, at 100+ FPS. Long answer: You have a "frame budget" which is the amount of time between rendering the super fast "slide show" of frames at 60+ FPS. This give…

It looks like the GPU is doing most of the work… from that point of view when do we start to wonder if the GPU can “offload” anything to the whole computer that is hanging off of it, haha.

Re: Simulating fluids, fire, and smoke in real-time

#26

Post by MaxBarraclough »

teh_infallible wrote: post #22
Valgrim wrote: post #19

Earlier quoted context omitted.

Now that LLMs run on GPU too, future GPUs will need to juggle between the graphics, the physics and the AI for NPCs. Fun times trying to balance all that. My guess is that the load will become more and more shared between local and remote computing resources.

Maybe in the future, personal computers will have more than one GPU, one for graphics and one for AI?

Many computers already have 2 GPUs, one integrated into the CPU die, and one external (and typically enormously more powerful).

To my knowledge though it's very rare for software to take advantage of this.

Re: Simulating fluids, fire, and smoke in real-time

#27

Post by softfalcon »

bee_rider wrote: post #25
softfalcon wrote: post #24

Earlier quoted context omitted.

> Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? Short answer: No, it's not "already busy". GPU's are so powerful now that you can do physics, fancy render passes, fluid sims, "Game AI" unit pathing, and more, at 100+ FPS. Long answer: You have a "frame budget" which is the amount of time between rendering the super fast "slide show" of frames at 60+ FPS. This give…

It looks like the GPU is doing most of the work… from that point of view when do we start to wonder if the GPU can “offload” anything to the whole computer that is hanging off of it, haha.

> It looks like the GPU is doing most of the work

Yes. The GPU is doing most of the work in a lot of modern games.

It isn't great at everything though, and there are limitations due to its architecture being structured almost solely for the purpose of computing massively parallel instructions.

> when do we start to wonder if the GPU can “offload” anything to the whole computer that is hanging off of it

The main bottleneck for speed on most teams is not having enough "GPU devs" to move stuff off the CPU and onto the GPU. Many games suffer in performance due to folks not knowing how to use the GPU properly.

Because of this, nVidia/AMD invest heavily in making general purpose compute easier and easier on the GPU. The successes they have had in doing this over the last decade are nothing less than staggering.

Ultimately, the way it's looking, GPU's are trying to become good at everything the CPU does and then some. We already have modern cloud server architectures that are 90% GPU and 10% CPU as a complete SoC.

Eventually, the CPU may cease to exist entirely as its fundamental design becomes obsolete. This is usually called a GPGPU in modern server infrastructure.

Re: Simulating fluids, fire, and smoke in real-time

#28

Post by imiric »

PKop wrote: post #20
CaptainOfCoit wrote: post #7

EmberGen is absolutely crazy software that does simulation of fire and smoke in real-time on consumer GPUs, and supports a node-based workflow which makes it so easy to create new effects. Seriously, my workflow probably went from spending hours on making something that now takes minutes to get right. https://jangafx.com/software/embergen/ I was sure that this submission would be about EmberGen and I'm gonna be hones…

Written in Odin https://odin-lang.org/showcase/embergen/

Odin is such a neat language.

I was equally impressed by Spall: https://odin-lang.org/showcase/spall/

Re: Simulating fluids, fire, and smoke in real-time

#30

Post by vlovich123 »

softfalcon wrote: post #24
bee_rider wrote: post #10

They mention simulating fire and smoke for games, and doing fluid simulations on the GPU. Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? It seems like running a CFD problem and rendering at the same time is a lot. Can this stuff run on an iGPU while the dGPU is doing more rendering-related tasks? Or are iGPUs just too weak, better to fall all the way down to the CP…

> Something I’ve never understood, if these effects are to run in a game, isn’t the GPU already busy? Short answer: No, it's not "already busy". GPU's are so powerful now that you can do physics, fancy render passes, fluid sims, "Game AI" unit pathing, and more, at 100+ FPS. Long answer: You have a "frame budget" which is the amount of time between rendering the super fast "slide show" of frames at 60+ FPS. This give…

> No one is using the iGPU for anything. It's completely ignored because it's usually completely useless compared to your main discrete GPU.

Modern iGPUs are actually quite powerful is my understanding. I think the reason no one does this is that the software model isn’t actually there/standardized/able to work cross vendor since the iGPU and the discrete card are going to be different vendors typically. There’s also little motivation to do this because not everyone has an iGPU which dilutes the economy of scale of using it.

It would be a neat idea to try to run lighter weight things on the iGPU to free up rendering time on the dGPU and make frame rates more consistent, but the incentives aren’t there.

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