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    Lighting discrepancy with ray traced reflections

    Hello,

    I'm trying to figure out what is causing the lighting to look different in ray traced reflections. I'm lighting a test scene using only a SkyLight with an HDRI image (ray traced shadows on, raytraced GI on and set to compute SkyLight). As you can see in the attached screenshot, everything in the chrome sphere looks brighter, the chiar and table look yellow instead of orange and the wall is almost white. There's no light baked in this test and the SkyLight is set to dynamic.

    In comparison, the second image is a screenshot from the "How to get the most out of ray tracing" video, showing a prefect mirror ray traced reflection that matches what's in front of it. What am I missing in my setup?

    Last edited by virtualHC; 08-18-2019, 02:50 AM.

    #2
    It seems this is an issue with SkyLight only, since rect lights and area lights render correct reflections:

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      #3
      To continue my struggle with ray traced reflections, after replacing the SkyLight with area lights, it seems that I can't get indirect light reflections to appear. Turning on or off r.RayTracing.Reflections.EmissiveAndIndirectLighting makes no difference and any object that is lit mostly by ray traced GI appears black in the reflections (see attached image). This is in 4.23.



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        #4
        Yeah, the fact that reflections don't support ray traced shadowed skylights, nor ray traced GI can lead to some very incoherent results. I hope they'll add support for all that sooner rather than later.

        Click image for larger version

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        ArtStation

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          #5
          Originally posted by The_Distiller View Post
          Yeah, the fact that reflections don't support ray traced shadowed skylights, nor ray traced GI can lead to some very incoherent results. I hope they'll add support for all that sooner rather than later.

          Click image for larger version

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          Thank you The_Distiller for your reply! I searched for long time and couldn't find that limitation stated anywhere (did I miss it in the documentation?). At least now I know it's just a feature limitation and not something I'm doing wrong.

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            #6
            Just curious here, what happens when you manually change the light color of the skylight on the chair reflection example? Are you seeing any tonality change in the reflections at all?

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              #7
              I've been seeing this problem too, and my solution (so far) has been to do a combination of reducing the usage of the skylight by darkening it and reducing its value. Basically reflections are currently overbright for the reasons stated above. I'm not seeing a way to get it to look right in every situation.

              I have seen that if you have an indoor scene, the most consistent solution is no skylight at all (that is if you want your reflections to show the value of the environment). If you transition from indoor to outdoor, you could ramp up a dynamic skylight intensity based on triggers. Mixed environments are tough right now.
              Stay in the Light on Steam
              https://www.youtube.com/watch?v=EI1_pqHMSCk

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                #8
                If you are using 4.23, you need to make sure your skylight is set to static. Stationary will add rasterized diffuse convolution to the secondary bounces, and movable will add it to both primary and secondary bounces. When the skylight is static, only then the raytracing seems to work correctly with it.
                https://www.artstation.com/artist/rawalanche

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                  #9
                  Is that in the documentation? How and where did you learn it needs to be set to static?

                  Wouldn't that harm it's ability to cast ray traced shadows? Or change its intensity value/color/other values using BP script?
                  Stay in the Light on Steam
                  https://www.youtube.com/watch?v=EI1_pqHMSCk

                  Comment


                    #10
                    Originally posted by The_Distiller View Post
                    Yeah, the fact that reflections don't support ray traced shadowed skylights, nor ray traced GI can lead to some very incoherent results. I hope they'll add support for all that sooner rather than later.

                    Click image for larger version

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                    hi,
                    is there any update or solution for this reflection issue?
                    thx

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                      #11
                      Did you test it with 4.23?

                      I’ll see if I can reproduce this issue. Maybe my Ray Tracing Tutorial will help you in the meantime.



                      cheers

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                        #12
                        Hi,
                        i use 4.23 yes.
                        If I use movable or stationary light, issue stays (everything reflected is too bright) If I use static skylight, the Reflection in the mirror (Metallic material) is on the contrary much darker then surroundings.. i will anyway check your tutorial!

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                          #13
                          Hi again,
                          went through you tutorial - really good one, thanks for that! But unfortunately I couldn’t find answer for the weird reflection issue there ...

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                            #14
                            Hi,
                            same here !

                            It actually seems that with an activated Skylight, the raytraced reflections do not work properly.

                            Click image for larger version

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                            It is very boring for the representation of an interior space for example ....
                            It's all the more annoying that the new HDRI Backdrop is really good to use, but it contains a Skylight inside;

                            Would someone have a track?​​​​​​​

                            thanks
                            https://pixel.network

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                              #15
                              HI,guys. I think I have a similar question ; in UE4 raytracing mode, when enable reflect shadow with hard shadow or area shadow and the room is small, the mirror or metal is black, they can't get the environment reflection from the near object; when I move the mirror to the out of the room,it perform right;

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