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Dynamic Pointlight Performance


I experience really poor performance with dynamic pointlights. I have seen this in several projects/ue4 versions especially with foliage, but also with other kinds of geometry. Literally when theres a place with like 10 trees and I add a dynamic pointlight with shadows enabled the FPS drop from about 90 to 15. It seems to be less expensive with other kinds of geometry, but still drains huge amounts of performance.

I have read up several topics in that regards over the time e.g. https://answers.unrealengine.com/questions/184262/47-adding-point-light-causes-massive-fps-drop.html but without a solution. Testing comparable scenes/setups with other Engines yield much better framerates. They are often more performant by a factor of 20 and higher. So there definitely must be something wrong on Unreal's side.

Theres also a huge drop when The Camera (editor or pie) moves into the pointlights radius - even when looking away from the light and not having any lit geometry in the view port.

Product Version: UE 4.12
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asked Aug 19 '16 at 04:35 PM in Rendering

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I never had performance drops like this. Shadowcasting from dynamic point light is indeed expensive on masked geometry, but 1 light would never cause such issues. How large is the radius of your light?

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answered Aug 20 '16 at 10:03 PM

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avatar image apgames Aug 21 '16 at 02:51 AM

I get this problem all the freaking time. Seriously sometimes just to keep framerate above like 11, I'll have to disable shadows on some objects completely, and I'll only have like 3 lights in the entire scene. I really hope some kind of solution is presented sometime soon.

avatar image Deathrey Aug 21 '16 at 05:44 AM

3 point lights with shadow enabled and large radius can easily destroy performance in a foliage heavy scene.

avatar image AlexW88 Aug 21 '16 at 03:23 PM

Rather small:alt text

These Shots are from different Projects and Engine versions (The Grass is from 4.12). Every Scene has a Directionallight, Skylight and Epic Settings. It was taken on a midlevel Intel CPU and AMD GPU, but I've worked with other people with all kind of Rigs, Combos and Quality settings having similar Results. Yes pointlights are "expensive" but this is just over the top, Comparable Engines yield much better performance with similar setups. Infact, most of the time other Engines render way faster with more point lights, bigger PL radius and higher Quality Settings. I don't want to say Ue4 is a worse engine, just "point" to an aspect that definitely could be improved.

I used worst cases for the screen, but even if you half the Impact of each PL its still terrible.

pointlight.png (1.5 MB)
avatar image Deathrey Aug 21 '16 at 06:53 PM

Hmm I don't think that is intended. I don't get considerable performance drop until I virtually flood the place with shadowcasting point lights. Gotta dig a bit deeper.

avatar image T3CHZ Aug 21 '16 at 07:51 PM

I also experience poor performance with any dynamic point-light in my projects, simple scenes decrease my fps substantially.

avatar image apgames Aug 21 '16 at 08:33 PM

I don't ever have the radius very far at all, since it simply isn't necessary. So basically I have the choice between lighting and foliage? I mean.... come on...

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