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    Originally posted by pf_breton View Post

    This exactly the way this solution could work.
    I kinda like it! There is one big BUT from my point of view though....and that is that most people dont have a lightmeter at hand to read the lux when they might capture a sky. Or what happens if you just buy skies from CGSkies.com? You dont know any lux readings as the image data is all you have. So the system needs to work without the need to buy fancy and expensive hardware.

    I think its a great option, but it should be just that...an option. There needs to be a working system that doesnt need you to specify that.

    In Frostbite, its actually that way that the skylight intensity also adjusts the brightness of the HDR image visible on the skydome (hard in Unreal since they are decoupled from each others...both approaches have ups and downs), so they are linked and thats already nice! However, we still only rely on the candela readings from the skydome as the actual candela values mean nothing cause different images could be captured differently. So we often have that situation that one sky is quite bright and another one quite dark and both are set to...like 5000 cd/m2 in the editor. So again, just measure the stuff on the dome directly and be fine

    Cheers!
    Check out UNREAL 4 Lighting Academy
    https://forums.unrealengine.com/show...ng-like-that-)

    Comment


      People shouldn't be forced to acquire extra hardware and have to capture own hdr sky textures. Because probably 99.95% of them just wouldn't.

      Prior to this new lighting stuff there were still over complicated ways of doing physically accurate lighting in UE4 but still, people just didn't do it, due to it being a complicated process + extra effort.

      If you develop new features for the engine make it usable for everyone in artistic friendly way.
      Last edited by Maximum-Dev; 10-26-2018, 07:42 AM.
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        Originally posted by Maximum-Dev View Post
        People shouldn't be forced to acquire extra hardware and have to capture own hdr sky textures.
        Nobody is required to buy extra hardware, you would be able to use any HDR you want and give it any intensity just like you currently can. You can find reference lux values online and could plug in an appropriate scale factor using that.

        Actually you can already do that by creating a perfect white diffuse sphere and using it as a light meter with the pixel inspector. Measure the skydome's influence on the sphere using pixel inspector, then doing some math and you can derive your skylight's lux (in the direction of the surface normal you sampled from the sphere). Still would be nice if pixel inspector showed luminance in cd/m2 instead of skylights. Example: I sample the top of a diffuse white sphere under skylight only and pixel inspector reads: 318.3 (cd/m2) surface luminace, because the sphere is perfect white diffuse, I can just multiply by pi to determine the skylight's illuminace is 1000 lux, (and if that is too dark or bright from the reference values I'm expecting, I'd have to scale my skybox materials instead of touching the directional light)

        I totally agree some features could still make the process more artist friendly.

        Comment


          Or what happens if you just buy skies from CGSkies.com? You dont know any lux readings as the image data is all you have
          no difference as today really... you’ll give an arbitrary lux value just like you’re giving an arbitrary intensity today. The only difference is that with a method like the proposed one, you will be able to have a physical reference if you happen to need one.
          Pierre-Felix Breton

          Sr Technical Product Designer AEC, Unreal Engine
          Epic Games - LinkedIn

          Comment


            I have question from different perspective.

            Will we get an Physically accurate procedural atmospheric sky ? Something like current Atmospheric fog, but something that actually outputs real Lux values which can be captured by skylight and which does not require HDRI texture.

            That would solve at least some of the problems
            https://github.com/iniside/ActionRPGGame - Action RPG Starter kit. Work in Progress. You can use it in whatever way you wish.

            Comment


              Originally posted by iniside View Post
              Will we get an Physically accurate procedural atmospheric sky ? Something like current Atmospheric fog, but something that actually outputs real Lux values which can be captured by skylight and which does not require HDRI texture.
              That's exactly what I'm thinking about.After all, how do we create an accurate day-night cycle?You can't find 24h skylight data online.

              Comment


                The current Atmospheric model works pretty well, but you just need to adjust your sun intensity based on angle, and probably the atmosphere's Sun Multiplier and other settings too. Finding sky information does seem difficult, but there's some decent reference for sun intensities. Here's one:
                http://stjarnhimlen.se/comp/radfaq.html#10

                You can then build angle-based sun intensity in to a blueprint. BP_LightStudio already adjusts color based on angle, so it's pretty easy to apply that to intensity as well.

                Here's an example using atmosphere to match a photographed HDR, but I had to use a Sun Multiplier of 25.0 to get the correct luminance/illuminace readings.
                Click image for larger version

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                Last edited by william.sch; 10-29-2018, 01:49 AM.

                Comment


                  A visual example of using a photographed HDR with photometric numbers in Unreal

                  Click image for larger version  Name:	unreal_lighting_sun.jpg Views:	1 Size:	113.4 KB ID:	1545013Click image for larger version  Name:	unreal_lighting_sky.jpg Views:	1 Size:	109.6 KB ID:	1545012Click image for larger version  Name:	unreal_lighting_both.jpg Views:	1 Size:	105.1 KB ID:	1545014
                  Pixel Inspector luminance readings on white sphere:
                  • sun light only: 4500 (cd/m2) = 14,137 lux
                  • sky light only: 1770 (cd/m2) = 5,560 lux
                  • combined: 6150 (cd/m2) = 19,320 lux
                  These match (close enough to) the illuminace readings I took on location
                  • 18,900 lux in sunlight, facing sun
                  • 5,000 lux in shade, facing same direction
                  • sun+sky - sky = 13,900 sun intensity
                  My actual Sun Intensity is 18,000 lux because its color is very saturated, something else to take in to account.
                  Skylight intensity is at 1.0 "cd/m2", although I still hope they remove the misleading unit label.
                  Pixel inspector show the deepest blue sky at about 720.0 luminance (cd/m2)
                  The skydome material emissive had a multiplier of 23,170 or 14.5 EV.
                  The HDR middle exposure (mentioned earlier) was at EV100 13.32, so I guess you can't just take the EV number and plug it in to your skydome emissive intensity, but it's close-ish. Again the difference is probably due to color saturation. It's always good to have illuminace measurements to be sure, but with most HDRs you'll never know the camera settings or illuminace at time of shooting.

                  The results came out okay. I can use manual exposure or EV100 numbers and it looks pretty close to what I'd expect. Something else to be aware of is I'm not using pre-exposure, so numbers around 65,000+ will start clipping, (at least on my hardware they do).

                  Click image for larger version  Name:	unreal_game1.jpg Views:	1 Size:	114.9 KB ID:	1545015Click image for larger version  Name:	unreal_game2.jpg Views:	1 Size:	101.5 KB ID:	1545016
                  Last edited by william.sch; 10-29-2018, 03:36 PM. Reason: typo fixed on sunlight intensity

                  Comment


                    Originally posted by iniside View Post
                    I have question from different perspective.

                    Will we get an Physically accurate procedural atmospheric sky ? Something like current Atmospheric fog, but something that actually outputs real Lux values which can be captured by skylight and which does not require HDRI texture.

                    That would solve at least some of the problems
                    Yes, sort of. The proposed approach is not incompatible with this at all. And for arch viz, we have a requirement of creating a parametric sky that delivers that. It’s all aligned in the same direction. A procedural Sky is similar to a photographed sky dome from a pixel intensity stand point.
                    Pierre-Felix Breton

                    Sr Technical Product Designer AEC, Unreal Engine
                    Epic Games - LinkedIn

                    Comment


                      Being long time Archviz artist, I've found that Atmospheric Fog in UE4 can work pretty well as a replacement for Physical Sky model often found in offline render engines. It unfortunately suffers from two severe flaws:

                      1, Screen space reflections do not work correctly with it, as they need some background geometry to establish depth. This can be partially worked around by introducing giant skybox sphere around your scene, but it often interferes with the Atmospheric Fog look.

                      2, Sun disc drawn on the Atmospheric Fog has completely wrong intensity. I've reported the bug here: https://issues.unrealengine.com/issue/UE-58668 and answer is "Won't Fix"... go figure. So at this time, despite Atmospheric Fog being a better Sky model for Archviz than Preetham or Hosek/Wilkie, it's bugginess and refusal of Epic to address these issues makes it unusable and UE4 will likely require yet another Physical Sky model on top of the existing one instead.

                      By the way, if the intent of the efforts is to make life easier for archviz people, then I would suggest implementing some 1-click algorithm, which would find HDR spots on the HDRI map (above defined intensity threshold), compute their radiance in proportion to the given scale, and automatically create Directional Light(s) with appropriate direction, intensity, color and source angle. That would save so much time.
                      Last edited by Rawalanche; 10-31-2018, 05:26 AM.
                      https://www.artstation.com/artist/rawalanche

                      Comment


                        Is the new "lighting academy" video of physical lighting coming?I need some explanation and you're the best on this

                        Originally posted by Daedalus51 View Post

                        I kinda like it! There is one big BUT from my point of view though....and that is that most people dont have a lightmeter at hand to read the lux when they might capture a sky. Or what happens if you just buy skies from CGSkies.com? You dont know any lux readings as the image data is all you have. So the system needs to work without the need to buy fancy and expensive hardware.

                        I think its a great option, but it should be just that...an option. There needs to be a working system that doesnt need you to specify that.

                        In Frostbite, its actually that way that the skylight intensity also adjusts the brightness of the HDR image visible on the skydome (hard in Unreal since they are decoupled from each others...both approaches have ups and downs), so they are linked and thats already nice! However, we still only rely on the candela readings from the skydome as the actual candela values mean nothing cause different images could be captured differently. So we often have that situation that one sky is quite bright and another one quite dark and both are set to...like 5000 cd/m2 in the editor. So again, just measure the stuff on the dome directly and be fine

                        Cheers!
                        Amberify Asset Pack | UE4.18 / 4.24
                        Neonfiy Asset Pack | UE4.18 / 4.24
                        Kinetica Asset Pack | UE4.23 / 4.24

                        Comment


                          Originally posted by Nocturness View Post
                          Is the new "lighting academy" video of physical lighting coming?I need some explanation and you're the best on this

                          There already is one Also, there wont be another one on this topic until Epic has sorted stuff out.
                          Check out UNREAL 4 Lighting Academy
                          https://forums.unrealengine.com/show...ng-like-that-)

                          Comment


                            Originally posted by Rawalanche View Post
                            2, Sun disc drawn on the Atmospheric Fog has completely wrong intensity
                            Yeah, definitely one of the problems. One of the many ways that Unreal tries to be user friendly but actually makes things difficult by doing so

                            Comment


                              Good feedback! As you know, arch viz being a driver for improvements in this area... our enterprise team is looking at those things. It’s not something that will go unnoticed!

                              As the technical product manager for this industry, i am taking good notes of the comments made in this thread.

                              If you judge from my background on linked in, you’ll see that the problems you pointed out are very close to my heart.

                              We’re looking forward to get it done right!


                              Pierre-Felix Breton

                              Sr Technical Product Designer AEC, Unreal Engine
                              Epic Games - LinkedIn

                              Comment


                                Originally posted by pf_breton View Post
                                Good feedback! As you know, arch viz being a driver for improvements in this area... our enterprise team is looking at those things. It’s not something that will go unnoticed!

                                As the technical product manager for this industry, i am taking good notes of the comments made in this thread.

                                If you judge from my background on linked in, you’ll see that the problems you pointed out are very close to my heart.

                                We’re looking forward to get it done right!

                                Man, thank you so much....this sounds absolutely fantastic and is much needed!

                                As you might have read already, I have been asking multiple times about the alignment between auto exposure and the cameras, mainly make auto exposure use the same ISO, Aperture (FStop) and timing settings so we can have gameplaystuff aligned with cutscenes (also, it just would be super helpful from an understanding point of view)

                                Any thoughts on this?

                                Cheers!

                                Check out UNREAL 4 Lighting Academy
                                https://forums.unrealengine.com/show...ng-like-that-)

                                Comment

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