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Occlusion Culling Issue

The video shows the issues I am having, but a brief run-down on here anyway:


I have disabled baked lighting and use a Directional light set to moveable casting dynamic shadows. I am using Modular SciFi: Interiors soo the level is made up of separate pieces placed next to each other like a jigsaw,

  • Light bleeds through certain sections of geometry. This could be because of the lack of backfaces to some of the gemoetry but I enabled two sided lighting/shadows or something like that.

  • I built lighting to top quality

  • The geometry seems to pop in/out based on where I'm looking, creating brief flashes of the sunlight (the outside world) as I turn around and go around corners etc

I cannot seem to stop this from happening and cannot be the only one who's seeing this sort of thing. Any ideas how to fix this?

Cheers Daz

Product Version: UE 4.8
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asked Jul 22 '15 at 09:46 PM in Rendering

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avatar image Logan Bailey ♦♦ STAFF Jul 24 '15 at 07:22 PM

Hello dazuk 1978,

I am currently looking into this issue and I will get back to you as soon as I am able.



avatar image dazuk1978 Jul 27 '15 at 02:36 PM

Hey Logan,

Thanks so much for looking into this for me. I will read the documentation and try your recommendations to fix it. I'll let you know if this sorts out my issues with the popping in, and indeed the light bleeding? It's not clear if sorting out the potential bounds issue will also fix the light bleeding issue, as this seems to be more about the geometry pieces not having back-faces. I tried building some BSP brush walls to block the light and if I do that then I don't get light issues - but that's kinda like taking a sledge-hammer to it rather than fixing the core issue, and creates other complications for me.

I'll update you with any progress I make, but I appreciate the time you've spent already on this.

Cheers, Daz

avatar image Logan Bailey ♦♦ STAFF Jul 27 '15 at 02:45 PM

Upon further consultation with fellow support I have been advised to tell you to not mess with the bounds. The most relevant situation for this would be for lights. If you are zoomed far out and the bound gets so small that the light no longer uses then bounds for calculation, then you could adjust to allow a light to behave as expected.



avatar image dazuk1978 Jul 27 '15 at 03:09 PM

Hmm. It did sound pretty logical but okay I won't mess with it. I guess the popping in is an auto-culling mechanism though right, kinda like a vis thing to cut down rendering things that aren't on-screen at any given time? Is there a way to disable this, as the millisecond pause between the thing not being on screen and being on screen is visible with the naked eye and as such causes the VERY bright outside world to momentarily be seen in the VERY dark interior.

As I said, I have shifted how I'm doing this for now instead of fighting against it and am currently focussing on asset creation and environment building, but it would be nice to have a solution for any further work I want to do using a Directional light as sunlight.

Thanks mate, Daz

avatar image Logan Bailey ♦♦ STAFF Jul 27 '15 at 03:14 PM

Yeah, so if you want to cut down on it and minimize the r.HBZocclusion 1 will work on a asset to asset basis.

To disable for the entire scene with no occlusion culling go to Project Settings > Rendering > Occlusion culling and turn it off.

Basically much of this is being addressed with it's development. At this moment there are ways to disable it and ways to minimize the affects.


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Hello dazuk 1978,

I narrowed the issue you are experiencing to a culling issue as opposed to a lighting issue.

What is occurring is the calculation of pixels and bounds whenever your object is off of the screen

Blueprint components, often times, can be set to inherit the bounds of their parent, which can cause issues if the parent has smaller bounds than the child.

I will link you to documentation that will elaborate further:


There are several work arounds

  1. Disable all occlusion culling for your screen by going to Project settings > Rendering > Occlusion culling and checking the box off. a.) Since you are wanting this utilized on static meshes this may not be the best option.

  2. In the viewport under Show > Visualize > Out of bounds pixels. Check this on and then enter the command r.VisualizeOccludedPrimitives 1 to see, in your scene what is being occluded behind what your looking at.

  3. The last option, is there is a console command r.hzbocclusion 1. This defines which occlusion is being used. This will allow for a more accurate calculation of your bounds.

More specifically in your meshes if the parent is exceeding the area of the bounding box then then the parts of the mesh will disappear or remain on the screen after the bounding box moves completely off camera.

Look into these options and documentation and let me know what you find,



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answered Jul 27 '15 at 02:00 PM

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