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Using emissive in lightmass - balance

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    Using emissive in lightmass - balance

    Hi, I'm just exploring UDK a little and wanted to check out the lightmass system.

    I am having a bit of an issue with the using emissive feature. You can see from the pic that it does not seem to be balanced, there is more blue light climbing up the pillars/walls on the right than on the left.

    This should not be the case, the light is coming from these little blue bulbs which are part of the floor section SM. There are 6 in each SM, 3 on each side, exactly the same distance away from the center.

    There are no other lights in the scene and the walls are an exact mirror image of each other, So I'm curious as to why there is more emissive coming from the right than on the left.

    Is it because lightmass is not designed to use such a big object for emissive lighting? (I see in the tutorials that the objects using this feature are single bulb style static meshes, not giant meshes with bits of emissive material scattered around).

    I tried seperating the bulbs out, and had to readjust the lighting, but generally got the same problem, where the light seems "weighted" in some areas, for seemingly no reason. Take a look at this pic, all of these lights are individual static meshes with the same emissive settings, why then are only some of them splashing blue on the wall (in various degrees no less)

    Dont get me wrong, I like randomness and I think with lighting it helps add to the realism of a level, but I'd like to be able to control it to a degree.

    The lights appear inset into the floor, have you tried raising them above the floor to see if that changes the effect you're getting?


      Lightmass system is similar to global illumination in other 3D renders which uses photons. You can see this effect more clearly if you decrease StaticLightingLevelScale value. It bounces off and takes color of the texture it bounced off from. So if it bounces off part of the wall that has more blue, it'll take blue color.

      If you want more control, I suggest using lights. But it will yield much more fake looking result. The irony is that this "unpredictability" is what gives you more realistic result. Can anyone paint a photo realistic scenery without using any reference? No because what you think should happen with lights usually is not realistic. When I render a scene in Maya with global illumination and final gather, I often don't get the result I expected... but it looks real.

      The 3rd image you posted, the randomness actually doesn't bother me and it would actually bother me more if all the lights had exactly same glow.


        Actually floor inset is what I was going for.

        I've learned a lot of little things can make a big difference in light. It's weird, I'm using a pencil sketch style of art (going from predominantly black/white with spots of color) and because the emissive light texture was sketched with strokes in a right diagonal direction that seemed to effect the balance of the light! Cool, but finicky

        Below is a screenshot getting more like how I want it to resemble. (obviously still need to add a lot of things)

        A number of things helped:
        I reattached the lights and added some geometry around them to provide a
        better "inset nest"

        I attached the walls to the static mesh (originally for level design reasons the walls and floors were in seperate meshes,but it seems to affect the lighting)

        I added 3 point lights (was going to do this anyway) distributed between the 6 static mesh hallway sections.

        Added I-beams (placeholders) to contain some of the light spill

        A couple things still bug me a bit:

        Lightmass seems to be aligning emissive light to verticies, not sure if theres a way around this. (see pic - adjusted to show light better)

        It's strange because those two adjacent lights are the same (literally polygons copy/pasted in max). You can see how the spill on the floor is aligning to the vertex.

        Also I'm getting some emissive mip-map style bleeding, where I have hard blue lines on the floor and ceiling when you get some distance away. I tried to change the LOD distance on the SM properties but to no avail. (You can barely see this in the first pic)

        All in all though, I'm happy with a first forray into UDK (havent used it since Unreal 2...was a cryengine guy, but more recently Unity for my last job.

        Coincidentally here's a pic of this same little concept level I'm making in Unity.

        Admittedly there's no lightmapping, but I put about the same amount of time getting it setup. With lightmapping much easier as well as Kismet (I'm a level designer by trade) I think I'm going to be using UDK to get this one rolling.



          Well, the issue I was having before was a matter of simply not having seperate lightmapped UVs on my meshes, I was confused because I thought lightmass took care of that automatically, but it wasnt difficult once I found out how (as with most things right?)

          I've learned a lot more about UDK in the past couple of days. I am changing to a new art style for my level prototype, its more realistic rather than the pencil sketch style I had above, but contrary to what I thought, it seems easier to do.

          Here is a pic of a couple of hallway pieces (ignore the clutter of meshes in front and behind) using just emissive lighting as before:

          Thanks to everyone who gave me advice!


            I can honestly say that you have improved your scene a lot. Keep it up