Light::DeferredSimpleLights

Development Rendering
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Light::DeferredSimpleLights(Strata:False,Tile:None) 33 draws 14256 prims 8151 verts

I have a lumen scene with 1 dynamic directional light. That is the deepest the profiling goes. I’ve done all sorts of optimizations and still get very bad fps due to lighting taking a lot of milliseconds. I’ve searched far and wide but haven’t found any good discussion / explanation / help / hints about how to further debug. Might anybody know the best way to get information on why the deferred lighting is taking so long? Do i have to resort to some external (e.g. nvidia) profiling and somehow read tea leaves from those? I feel like this must have cropped up as a perf problem for a lot of people over the years…? Thanks for any thoughts.

some misc notes:

  1. used large post process volume (1k,1k,2k scale) to set global illumination to None, Reflections to None.
  2. used Reduction Settings on static meshes to bring down vert/tri counts.
  3. there’s only 1 directional light, it is movable, i turned off casting shadows. i don’t need it to be movable. i just don’t ever fully understand what happens to lighting if i make it anything else. i don’t want to get back into ever having to “build lighting” at least.
  4. profiling shows the DeferredSimpleLights is what is killing frame rate, but there’s no more lower level detail to help me see exactly what it is doing in there.
  5. not using nanite, i don’t have anything that would particularly fit that.
  6. according to Tools>Audit>Statistics, scene has 338k tris.
  7. have been making some materials unlit in the hopes it would help.

very stressfully, after trying these kinds of changes, i now somehow have even worse fps, and no way to know why the DeferredSimpleLights is only getting worse. :frowning:

I just tried using the Shader Complexity view in the editor. There are some white areas that have high PS and VS. They are mostly P_Fire and P_Sparks. I’ve used those in other levels w/out seeing any frame rate issues fwiw… at least I will experimentally try deleting those to see if it changes the fps.

(Light Complexity visualization shows almost everything is pegged white which I super don’t understand. How can I know what that means and what I can do about it, other than that I am doomed at the moment heh? It makes no sense to me since I only have 1 movable directional light in the scene. Light Complexity Freaking Out - #4 by Shmann uh, yeah, so confusing.)

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Update: I had a physics mannequin flying around in zero g. It has a lot of triangles. Setting the materials to be unlit on it seemed to maybe help. I also deleted a lot of particle fx (that were all cascade). None of those things cause me trouble in any of my other levels, so it is really voodoo weird stuff. So this is just completely a random guessing game since it seems like the profiler can’t say anything more detailed than “deferred lighting is hard let’s go shopping”?

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Of course in another different (landscape, rather than interior) level I am now getting low FPS and I can’t get any lower level detail than just “Light::DeferredSimpleLighting” yay, and I already did the non-shaded-material-on-the-mannequin trick so… yeah. I have a large post process volume around the world and have disabled reflections, didn’t fix the low fps, then i also am trying non-lumen global illumination ie screen-space, but that is just as bad as lumen if not worse.