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  • started a topic 4.19 Physical Lights

    4.19 Physical Lights

    Hi I have a small question about the new 4.19 physical lights, the new version has changed the intensity to a choice of Candelas, Lumens and Unitless. I understand the difference between Candelas and Lumens, and that Unitless is the old 4.18 and older system, but in 4.18 and older I thought the intensity was a direct value of lumens if inverse square falloff was turned on?
    If this is the case then what is the difference between the new Lumens and the old Unitless? I have tested a point light in the exact same scene in 4.17 and 4.19 with point lights with 1700 intensity/lumens, in the 4.19 scene the new Lumens setting is a lot brighter than the 4.17 scene. Of course if I switch the light to Unitless they become the same. What is the difference between the 2 models? If the 4.19 lighting model is the 'correct' physical lighting model, does that mean that 4.18 and older were using a wrong model?

    Anyone know what the difference is between the new lumens and the old 4.18 lighting system?

  • replied
    Originally posted by DP Studio View Post
    Bugs I've encountered while using the physical units, most are a result of the share amount of lux used and the needed support of the old unitless system:
    ...
    Although shelved, LPV is blown as well due to required exposure and/or lux levels.
    ...
    It seems to me LPV's break as soon as you start increasing directional light brightness ever so slightly.
    At 128K lux you more or less only get primary colors. :/

    Leave a comment:


  • replied
    Originally posted by imbakeks View Post
    Hi all,

    I am following this thread since it started and also was playing around with the system. Eventually, I started to put together all the information in a comprehensive talk which I held at the Unreal Meetup Munich last week.

    As I learned a lot by you guys (many thanks to all of you) I wanted to share my slides with you which should be a good reference for looking up lux values etc. You can find them here: Physically Based Lighting in Unreal Engine 4

    For me, it worked best to have a mixture of the above mentioned workflows meaning using the Sunny16 chart for initial camera, sky and sun light setup (using the 35-125k lx range), then measuring the received light by using a white fully rough card or sphere and comparing it with the tables until I reach a correct looking light condition which matches with the values. Especially the breakdowns of sun and sky illuminance for some conditions in the lux table help a lot! Finally, I convert the camera settings to EV values for setting up auto exposure and applying some offset to the min ev value.

    Probably worth mentioning that I was solely using fully dynamic lights for now.
    Thanks for that! Very comprehensive quick guide.

    Leave a comment:


  • replied
    Originally posted by DP Studio View Post
    Bugs I've encountered while using the physical units, most are a result of the share amount of lux used and the needed support of the old unitless system:
    Broken planar reflections due to required lux levels.
    Broken local lights due to required exposure levels.
    Some gismos and visualisers are not visible due to required exposure levels.
    Legacy emissive materials not visible due to required exposure levels.
    Although shelved, LPV is blown as well due to required exposure and/or lux levels.
    Exponential Hightfog barely rendering, if not at all...
    You can add Scene Capture Cube to that list, hope to see some fixes THIS year...

    Leave a comment:


  • replied
    Very interesting informations here.
    Thanks for sharing Lukas.

    Leave a comment:


  • replied
    Hi all,

    I am following this thread since it started and also was playing around with the system. Eventually, I started to put together all the information in a comprehensive talk which I held at the Unreal Meetup Munich last week.

    As I learned a lot by you guys (many thanks to all of you) I wanted to share my slides with you which should be a good reference for looking up lux values etc. You can find them here: Physically Based Lighting in Unreal Engine 4

    For me, it worked best to have a mixture of the above mentioned workflows meaning using the Sunny16 chart for initial camera, sky and sun light setup (using the 35-125k lx range), then measuring the received light by using a white fully rough card or sphere and comparing it with the tables until I reach a correct looking light condition which matches with the values. Especially the breakdowns of sun and sky illuminance for some conditions in the lux table help a lot! Finally, I convert the camera settings to EV values for setting up auto exposure and applying some offset to the min ev value.

    Probably worth mentioning that I was solely using fully dynamic lights for now.

    Leave a comment:


  • replied
    I wonder if we will ever see some sample scenes from the Unreal team itself. It would be nice to have 4 or 5 pre-set scenes (mid-day, cloudy, sunset, night, interior) to take as reference.

    Leave a comment:


  • replied
    Originally posted by DP Studio View Post
    Bugs I've encountered while using the physical units, most are a result of the share amount of lux used and the needed support of the old unitless system:
    Broken planar reflections due to required lux levels.
    Broken local lights due to required exposure levels.
    Some gismos and visualisers are not visible due to required exposure levels.
    Legacy emissive materials not visible due to required exposure levels.
    Although shelved, LPV is blown as well due to required exposure and/or lux levels.
    Exponential Hightfog barely rendering, if not at all...

    I'm still new to all of this bull-shittery so take wut I say with a grain of salt :P
    I don't quite follow your reasoning behind using unitless, since as long as Inverse Square Falloff is enabled, the output is identical, it's just expressed as a different unit... or lack there of for unitless.

    Planar Reflections don't look like they use Pre-Exposure. They work correctly for me in extremely bright scenes with physical units without Pre-Exposure, but get blown out once it's enabled.

    Broken local lights/legacy emissives due to exposure levels - I'm assuming this is saying you can't see a light because the exposure/relative luminance is too high? Well then that's to be expected. Take a flashlight outside in the direct sun and tell me if you see it If you want to see emissives at all times, regardless of auto-exposure, then divide your final emissive output by the EyeAdaptation node and it will maintain a consistent luminance.

    The Exponential Height Fog issue is identical to the above one. By default, the luminance of the fog is super low, so you need to change the color value to something much higher.

    Leave a comment:


  • replied
    If anyone was wondering, I think 1 unitless = 4,000lux and the same 4,000 for unitless>cd/m2.
    Eample... 3.14unitless = 12560lux
    For sky cd/m2 get 5% of the directional lights intensity (628cd/m2 if the directional light is 12,560)

    Tested at EV0 for unitless and EV12 for physical.

    I've got a blueprint set up to convert from lux to the unitless sytem and I haven't noticed any difference using the 1:4000 system assides from the difference in the rendering
    Default unitless (20.96)
    Physical values (83,850)

    Bugs I've encountered while using the physical units, most are a result of the share amount of lux used and the needed support of the old unitless system:
    Broken planar reflections due to required lux levels.
    Broken local lights due to required exposure levels.
    Some gismos and visualisers are not visible due to required exposure levels.
    Legacy emissive materials not visible due to required exposure levels.
    Although shelved, LPV is blown as well due to required exposure and/or lux levels.
    Exponential Hightfog barely rendering, if not at all...

    I'm still new to all of this bull-shittery so take wut I say with a grain of salt :P
    Last edited by DP Studio; 04-17-2019, 03:32 PM.

    Leave a comment:


  • replied
    Hi all,
    Not directly linked with physical lights, but we need this tool to calibrate the light......
    Has anybody try to use pixel inspector with 4.22 and ray tracing activated (dx12)?
    It seams to not working (by the way, by lauching unreal with dx11 it's ok)

    Leave a comment:


  • replied
    Do either of you have Pre-Exposure enabled in the Project Settings? That has been the fix for going out of range in the past.

    Leave a comment:


  • replied
    Originally posted by Sir_Manfred View Post
    I tried getting it to work in both 4.20 and 4.21 but couldn't get a result that wouldn't make things like the sky and/or the metallic materials look weird. Any metallic surface would get their shiniest highlights turn black when everything broke.
    Is there perhaps a setting I was overlooking?
    I had the same result, and I thought it was known to be broken. maybe I also overlooked something?

    anyway I'll try again in 4.22 sometime soon

    Leave a comment:


  • replied
    I tried getting it to work in both 4.20 and 4.21 but couldn't get a result that wouldn't make things like the sky and/or the metallic materials look weird. Any metallic surface would get their shiniest highlights turn black when everything broke.
    Is there perhaps a setting I was overlooking?

    Leave a comment:


  • replied
    Originally posted by TCBmbw View Post
    Hi guys,

    I'm just looking for some advice here. I'm following the thread (and tutorials) for a couple of month and I'm also pretty disappointed and confused with this sloppy implementation.
    As a 3D Artist, not lighting artist, I want to use physical lights without a rocket science degree or 1000 workarounds.

    To sum it up - at the moment physical lights are not working properly and I have to eyeball stuff anyway, right?
    So would you suggest to use the "old" exposure workflow and wait till this feature is implemented properly - why should I invest time in something, which does not work the way it should?
    This is no rant, I just ask for some advice regarding this confusing topic. At least, for me it masks no sense to guess (actually breaking) lighting values in an actual physical lighting setup (?).

    Thx
    As of 4.20, everything should be working correctly. There is an issue with Pre-Exposure and Planar Reflections, but that's the only thing I've noticed aside from the various workflow changes people want.

    Even with Physical Units, you will still be eyeballing things, they just make it easier to get to a starting point. Some characteristics of physical units aren't accurate unless you have all the information, like lumens and radiation patterns, lux and season, locale, etc

    Leave a comment:


  • replied
    Hi guys,

    I'm just looking for some advice here. I'm following the thread (and tutorials) for a couple of month and I'm also pretty disappointed and confused with this sloppy implementation.
    As a 3D Artist, not lighting artist, I want to use physical lights without a rocket science degree or 1000 workarounds.

    To sum it up - at the moment physical lights are not working properly and I have to eyeball stuff anyway, right?
    So would you suggest to use the "old" exposure workflow and wait till this feature is implemented properly - why should I invest time in something, which does not work the way it should?
    This is no rant, I just ask for some advice regarding this confusing topic. At least, for me it masks no sense to guess (actually breaking) lighting values in an actual physical lighting setup (?).

    Thx
    Last edited by TCBmbw; 04-10-2019, 12:37 PM.

    Leave a comment:

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