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  • Lightmass: multi-bounced sky lighting

    Edit: Fixed a bug that causes all lights to lose their first bounce (second and later on is preserved). The binary and GitHub repository are updated.

    Binaries, replace Engine/Binaries/Win64/UnrealLightmass.exe directly:

    4.15: https://www.dropbox.com/s/v3watjmkpp...tmass.zip?dl=0

    4.16: https://www.dropbox.com/s/fgs47wmzob...-4.16.zip?dl=0

    GitHub source: https://github.com/AlanIWBFT/UnrealE...yLighting-4.16

    Hint: This mod can be used together with a modified BaseLightmass.ini to get a better result. (especially the CachedIrradiancePhotonDownsampleFactor parameter, default is 2, highest is 1. If you have troubles with small features of the lighting, you can set it to 1, together with a smaller Static Lighting Level Scale)

    Single bounce vs 10 bounces:

    Brighter in deep space:
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    Much better color bleeding effect: (Colors are also more vivid)
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    Removes overdarken corners:
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    Helps to wash out artifacts:
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    RealisticRendering demo, single bounce vs 7 bounces:

    Lit by a single skylight:
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    With sun (a directional light) and other spot lights:
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    Notes:

    This feature is implemented with a radiosity-like technique. The drawback is that the time of "Caching Irradiance Photons" (orange bars in SwarmAgent) will scale linearly with bounce number.

    However, this technique allows even the deepest object to get a solid bounce, which is what we want from a multi-bounced sky light:

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    My own test shows that 5~10 bounces can get very nice results, so it may not be a good idea to raise the bounce number to some crazy things like 50 or 100.
    Attached Files
    Last edited by Luoshuang; 07-06-2017, 05:39 PM.

  • #2
    I thought bounces after 10 were much quicker than the first 10.

    Comment


    • #3
      Originally posted by ZacD View Post
      I thought bounces after 10 were much quicker than the first 10.
      Well, it is true for photon mapping, but sky lights are not handled with PM in the official Lightmass, so is it here.

      Edit: it may be better to use PM for sky lights, but that is a little bit complicated for me to implement...

      Comment


      • #4
        Out of curiosity, I'd love to see some comparisons with some finished scenes, like the community stuff on the market place or even the Robo Recall starting level. I'll probably try it myself at some point, but more comparison shots are always nice.

        Comment


        • #5
          From my own experience, the difference between single and multiple bounces will become less significant in a level finished with detailed textures; This feature is mainly intended for ArchViz where you have things like clean white walls. On the other hand I haven't compared it to Koola's bounce-card technique, which gives you more control about lighting.

          Comment


          • #6
            Koola updated his scene in 4.13(?) to only use portal lights. But I did notice Epic did use bounce cards for the Robo Recall starting level. Most people have said you don't need bounce cards anymore.

            Comment


            • #7
              Originally posted by ZacD View Post
              Out of curiosity, I'd love to see some comparisons with some finished scenes, like the community stuff on the market place or even the Robo Recall starting level. I'll probably try it myself at some point, but more comparison shots are always nice.
              I did some quick tests with the RealisticRendering demo:

              [Images moved to main post]
              Attached Files
              Last edited by Luoshuang; 06-15-2017, 09:37 PM.

              Comment


              • #8
                This looks fantastic. Do you have any clue why this isn't a native feature?

                How long did it take you to implement if you don't mind my asking, and are there any limitations or drawbacks to multiple bounces for SkyLights?

                I'm trying to understand why Epic wouldn't have added this feature themselves already.

                Comment


                • #9
                  Originally posted by mechanicalsnowman View Post
                  This looks fantastic. Do you have any clue why this isn't a native feature?

                  How long did it take you to implement if you don't mind my asking, and are there any limitations or drawbacks to multiple bounces for SkyLights?

                  I'm trying to understand why Epic wouldn't have added this feature themselves already.
                  Currently skylights are not handled with photon mapping in official Lightmass.

                  It should be better to handle them with PM, I think they simply haven't got there yet.

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                  • #10
                    this is awesome :]

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                    • #11
                      I tested it on one of my test scenes and the color bouncing, even in not direct light, seems to be much better and more pronounced. Looks great.

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                      • #12
                        Originally posted by ZacD View Post
                        I tested it on one of my test scenes and the color bouncing, even in not direct light, seems to be much better and more pronounced. Looks great.
                        Glad to hear that

                        Comment


                        • #13
                          Some more results about the color bleeding effect:

                          [Images moved to main post]
                          Last edited by Luoshuang; 06-15-2017, 09:38 PM.

                          Comment


                          • #14
                            You should definitely post this in Architectural Visualization as a new thread, they'd love it.

                            Comment


                            • #15
                              This is fantastic! I recently gave up on using a Skylight for arch-viz because of the one bounce limitation, so I'm very excited to give this a try today after work.
                              The results you posted sure look great!
                              My Porfolio

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