I have RTX 4090 GPU and it gives me high FPS in my game development but does not give enough video memory for some nice features (such as water). Will the second 4090 double the VRAM, and won’t they interfere each other so much that the speed will be less than on one such GPU?
P.S. Quadro is not a variant for me in any case.
I don’t think I’ve ever heard of anyone maxing out a 4090’s VRAM doing anything less than serious simulation work or extreme micropolygon sculpting. When you say water, do you mean UE’s tesselated water renderer, or something like actual fluid simulation?
1 Like
short answer is no. sli and nvlink are deprecated and the memory will not add up, since neither gpu can access the video memory of the other. they can render frames in tandem, but each gpu can only use the memory that’s local to it.
2 Likes
You’re using the PT then I take it?
Sounds cool but if dual 4090s don’t have enough VRAM for your game, who will buy it? 
I mean the water bodies that are inside the “Water” plugin.
So the VRAM will remain 24 GB? Or is it possible, for example, render water on one GPU and all the other landscape on the other GPU? Or split memory consuming in some other way?
Can you explain in a more detailed way? Does it mean that I can have multiple GPUs and assign them different “tasks”, for example, different cells of landscape, and each GPU will render its “task” using its local memory? Or this case is not possible?
I do not understand you.
- Now I have just a single 4090, and I am very hoping that dual will be enough to render that horrible water.
- This amount of VRAM is necessary only for the editor, which needs to render the entire landscape at the same time and also many debug features and the editor environment itself. The packaged game, of course, will consume much less resources.
The path-tracer, the photorealistic offline rendering solution that unreal has. What I’m fundamentally confused about is how you need two 4090s to render anything in unreal, because my card has half of that and a great deal less compute power, and I’ve never hit any limitations. Even when rendering large amounts of landscape data I normally don’t have issues, unless you’re using a custom solution?
TL;DR I’m wondering if there’s a bug or memory leak in UE.
Actually I use the path tracer from yesterday, but in very small amounts, it is not linked with the water and is not the source of the problem.
How many landscape proxies do you have and how large is each of them? I have 32 proxies of size 2x2 km.
What version of UE are you on? One of the new features as of 5.3 is a memory analysis system that lets you see what each individual asset is occupying in regards to your whole memory pool. If one asset is hogging inordinate amounts of memory, it could help to diagnose:
BIG thing: are any of your assets nanite? Enabling nanite can vastly shrink an object’s disk size.
5.2.
It is only in 5.3? And not present in 5.2?
I am using Nanite on all static meshes except translucent ones and those which have hundreds of thousands of polygons.
But can you please return to main topic?
I’m more than happy to, my apologies, I’m just quite baffled that you don’t have enough VRAM to handle water with a 24GB card.
Connecting the two without SLI is probably quite challenging to do in an efficient way. If you’re rendering things for MRQ or such you could probably have it treat the other GPU as a render agent, but I honestly don’t know if it’s possible.
Evidently, it is available for UE 5.2!
1 Like
Short answer: No.
So, there is not a way to render the water in the big open world? Or the only way is Quadro (that is unreal for me)?
EDIT: and is this a fake?
I think at this point I’ll just say this is probably out of my depth. You’re dealing with systems features that I’m just not familiar with and I haven’t seen a lot of people using to begin with. It very well may work, but I don’t know anything about them. I might try finding out which team was in charge of the feature set, looking for a feedback thread, and asking them directly?
What is “the water”? Which specific shader and actor/component?
Typical water/wave shaders aren’t particularly heavy duty.
I hadn’t seen the nDisplay support. That looks cool, although probably also experimental 
Seems targeted mostly for large film stages, CAVEs and similar.
So it seems like “long answer: try that!”
If you get that working for you, please report back!
Really? Have you ever tried adding lake, river or something similar to the landscape of size at least 12x12 km? I have tried many times and each time the editor crashes.
crashing? i’d recommend you update to 5.3. it’s got a way more stable vram manager.
as for doing math: according to documentation a full blown 8kx8k terrain takes roughly a gigabyte of memory. out of my budget but it manages it. i dare to try brush something in the chunks. this geo is dense. i lagged in another demo project already.
a water plane should be cheap af. the only other factors you may have to deal with is shadow maps or vsm lod management. and ofc your foliage assets. you should run some memory diagnostic. figure out what’s blowing it up.
having tried it… 24 gigs should be enough for a humble and optimized terrain setup.
1 Like
I have just tried the same on the 8x8 km landscape and have gotten a radically different result. With all the graphical features left without changes the VRAM is near the cap but without exceeding. Somewhy the “basic” landscape created from the “Create” menu and the extra cells differ in the resources consuming hugely. Thanks everyone for the answers, I have learned much new information! But the 8x8 km landscape won’t be able to be present in the game forever, so the topic about Multi-Process Rendering leaves actual.
8x8 kilometers at what resolution, I’m curious.
UE has a new system that allows you to bake landscape to a nanite mesh to save on perf. You could theoretically bake your landscape to nanite and use the bake, once you reach a form you’re happy with. That would cut a very large amount of memory consumption.
What means “at what resolution”? The component size is 255x255 quads and 1x1 sections.
But, to form that landscape at least the first time, one needs enough VRAM. Also I’m not sure that the water will work as the mesh.