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No Dynamic GI/ LPV?

Hey all, I found some other forum posts regarding this issue, but I couldn't find a solution to my issue, so here goes. I have added the command "r.LightPropagationVolume = 1" in my consoleConsoleVariables.ini, In World Settings I have "ForceNoPrecomputedLighting" set to enabled, And I have a light source set to moveable and in its properties, "Dynamic Indirect Lighting" Is enabled. Engine was restarted for the .ini files to take effect, and I have rebuilt lighting to refresh the rendering.

For some reason, im not seeing ANY light bouncing, Or Light Bleeding, such as having a box with a gold reflective texture next to a box with a silver reflective texture. This is quite odd, as months ago, I was using and enabling this function constantly in engine builds, any ideas guys?

Product Version: UE 4.9
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asked Nov 01 '15 at 03:49 AM in Rendering

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3 answers: sort voted first

You need to have a movable directional light in the scene. Before 4.9 dynamic emissive lighting worked only when there is a directional light in the level. With 4.9 they added LPV support to point lights(or spot lights, i cant remember which one) so they may need a directional light as well in order to work. I havent been able to use LPV on 4.9 yet so i cant give you an exact answer but those should at least help you eliminate the possibilities.

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answered Nov 01 '15 at 04:55 AM

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avatar image Tosaka Nov 01 '15 at 05:16 AM

I attempted to do as you recommended, by adding in a moveable Directinal light, setting it to Dynamic Indirect Light in its properties, but its still refusing to offer any emissive lighting for me, heh. I also looked into point lights, but alas, no such luck, any other ideas?

avatar image Tosaka Nov 01 '15 at 04:45 PM

alt text

Unsure why it wont let me resize this picture, but here are my settings in editor. Hope this helps...

avatar image Tim Hobson ♦♦ STAFF Nov 01 '15 at 09:30 PM

Trying using the Viewport > Show > Visualize > Light Propagation Volumes view mode. If this is working then LPV has been enabled for your project. If you're not seeing anything there it's not been properly enabled. Just something to check to be certain.

Also, the World Settings for Lightmass don't really matter since that is only related to building lighting with static lighting. Dynamic lighting will not use any of those settings.

avatar image Tosaka Nov 02 '15 at 08:46 PM

Heres the result: alt text

I'm assuming the light field im seeing shows Dynamic GI is enabled, but diffuse and light bleeding, it just looks different from the eariler generations, like theres nothing there.

avatar image Tosaka Nov 03 '15 at 03:21 AM

I installed Unreal Engine 4.5 to compare my eariler settings with the current settings, to see if there was something I've missed. I set the same settings for the engine in 4.5, and enabled Dynamic GI. Here's the result: alt text

So the issue must be somewhere else. Is Dynamic GI broken in 4.9? Or am I missing something?

avatar image Tosaka Nov 03 '15 at 09:42 PM

I checked the preview for Unreal Engine 4.10 preview 4, and althought it's only a temporary build, it still has all the stock settings that a normal build should have. Visualizing the Light Propagation Volumes in view settings does show that somethings enabled, but no textures are bouncing off others, such as gold textures bouncing off a pure white floor, ect. I'm assuming Dynamic GI is enabled, but no diffuse or color bouncing is working. So does anyone have any experience working with LPV in 4.9 builds? alt text

alt text Heres the two engine comparisons next to each other.

Here's 4.5.1 And here's 4.9.2 alt text

avatar image Tim Hobson ♦♦ STAFF Nov 04 '15 at 04:27 PM

Doing a quick test in my LPV Test scene I've got LPV working using the steps that have been outlined in the documentation pages with no issue.

Here is my sample images.

LPV Enabled in Light Source alt text

LPV Disabled in Light Source alt text

Visualization of LPV alt text

It can be easier to test LPV stuff if you make a scene similar to mine that way you can create something rather easily that should have light bounce. It can be much easier to see the bounce and color bounce for testing. This way you can rule out where your issues are.

Also add a post process volume to your scene that is unbound and adjust some of the properties in the Light Propagation Volume section.

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Tim, I've verified that LPV is enabled, so I'm guessing thats not the issue. The issue is the differences between these two pictures.

alt text

alt text

The Top picture is Unreal Engine 4.5.1. The bottom picture is 4.9.2. Both pictures are of the same project, same settings, LPV enabled in the .INI, everything should be the same. Perhaps it's not the LPV i'm missing, its the glow or diffuse light scattering that im seeing thats the issue.

I'm in no way that knowledgeable with Unreal engine's rendering abilitys, so forgive me on this one, i'm just at a loss as to why the newer engine version has much, much darker light bounces, no progressive glow on the gold and copper textured boxes(in both pictures). I'm not trying to be difficult, honestly I'm not, I just want to understand what the difference is, and where I can make the adjustments in my 4.9.2 projects and later so they look just like the pictures from my 4.5.1 projects.

If I can't figure out this, i may just have to stick with 4.5.1, but I'd like to think i'm doing something wrong, heh. Thanks for your patience.

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answered Nov 04 '15 at 10:55 PM

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avatar image Tim Hobson ♦♦ STAFF Nov 05 '15 at 03:27 PM

I honestly, can't say what the different between a version of the engine from over a year ago and one that is currently available. Epic does not develop the LPV lighting system. This is all code that has been developed and submitted for everyone's use by Lion Head Studios (the Fable game series). There have been some code changes through-out the development of the engine that has been submitted, the most recent being for 4.9 that I'm aware of.

Aside from just LPV there have also been a lot of changes to the engine in general that could cause these issues that you're seeing.

There also appears to be a lot of stuff going on in your scene that can make it hard to narrow down. Try using non-metallic materials so that you don't have SSR interfering (you can change this after the fact, just helps to see things more clearly), disable bloom and lens flare, and set the auto exposure min/max values to 1.0. This will give you a much more consistent scene to see what's going on.

At that point, you can start adjusting the LPV options in the post process to tweak and view the bounce much more easily.

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Much thanks Tim, ill look into these options. At least I have a direction now^^

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answered Nov 06 '15 at 12:12 AM

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