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How to support low-end gpu's with Unreal?

I have two low end GPUs that are in my group of testing machines. One is an ATI Radeon HD 3870 and the other is a Intel HD Graphics 4600.

I understand that these are low end gpu's. However, they can run other AAA games like Dark Souls 2, Dota 2, LoL, Skyrim, Fallout 4, etc.

However, when I create a BLANK UE4 scene that is rendering absolutely nothing my FPS hovers between 28 - 30 (on the Radeon HD 3870 with only 512MB of vram).

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I can obviously see that the GPU is the bottleneck. But why would it be under heavy load when I'm not rendering anything?

What would the GPU be doing that takes this much time? It has nothing to render....

This is just a test because with my real project I am getting lower than expected performance and would like to understand what I can do to optimize.

Also, I hope the only graphics quality setting solution that we have isn't to make everything extremely blurry?

I love UE and I know all the devs have insane gpu's but come on...

Edit: I have been looking at it with ProfileGPU to try and see what is going on. Here is the output. alt text

So, I disabled TranslucentLightingVolume with the following r.TranslucentLightingVolume 0. However, that caused StandardDeferredLighting to jump up to 32.64ms.

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The last "Downsample" also seems way to high a lot of the time. For example, I've seen 9 - 15ms frames. I'm not entirely sure how the downsampling works. But would love to find out.

Product Version: UE 4.10
blank.png (30.7 kB)
blankproject.png (285.9 kB)
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asked Jan 10 '16 at 08:09 PM in Rendering

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avatar image Erasio Jan 10 '16 at 08:46 PM

Is that data from clicking play in the editor or standalone?

That's the first thing I can think of. The editor adds a huge overhead on everything.

avatar image erebel55 Jan 10 '16 at 09:15 PM

It is from a standalone. I'm adding some ProfileGPU information to the post now.

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2 answers: sort voted first

The fact that the project is blank doesn't mean it will render at 9999 FPS. If you have the quality settings turned up to max, it's still going to have a very high cost (relative to old GPU hardware) to draw/shade every pixel on the screen, even if there's just a sky sphere, one light and a ground cube in the scene.

Things you can do to speed up rendering:

Turn off transparent lighting features. Turn off motion blur. Turn off HDR eye adaptation. Lower the dynamic shadow (CSM) quality by reducing the number of cascades, the filtering quality, and the resolution of the shadow maps. Lower the SSAO quality and reduce its radius. Disable the lens effects (aberration, dirt mask, etc.). Disable lens flares. Disable bloom or lower the radius and quality. Use ScreenPercentage to undersample the rendered image.

The profile GPU outputs can be misleading sometimes. The high usage for certain things changing as you disable features may just be shuffling the same set of work into a different phase of the rendering flow.

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answered Jan 11 '16 at 12:39 AM

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avatar image erebel55 Jan 11 '16 at 01:10 AM

I don't even have the sky sphere, light, etc. My scene is literally blank and just renders black. Which is one of the main reasons I was surprised. Seems odd that it would take more GPU power to render black pixels. Regardless, this is very useful information. I will keep playing around with the settings and ProfileGPU. I appreciate you help :)

avatar image cancel Jan 11 '16 at 01:16 AM

The color of the pixel doesn't matter. The same shading code (basically) runs for every pixel on the screen, along with the postprocess effects, etc.

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Hallo , pls am running on a 2Gb Nvidea GT 750. Pls i need clarification as to whether or not UE4 can run okay on my laptop?


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answered Aug 07 '18 at 12:04 PM

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