New physical exposure broken with directional lights

Hi Epic!

Firstly, great work on beginning to integrate the much needed physical units for cameras and lights. With the 4.18 improvements to lightmass this has the potential to be immediately valuable to those of us used to already working with real units elsewhere.

With that said, when testing the new physical lights and exposure settings I’ve noticed that while it works perfectly with spot and point as expected, the system completely falls apart when you begin to work with directional lights. This has been tested in a project using full realtime lighting w/ distance fields as well as in a clean project using lightmass.

My process has been this:

  • Get a basic setup of a directional
    light, skylight, skysphere,
    importance volume, PP volume, etc
    etc.
  • Review all settings related to
    lighting for sanity
  • Set the PP to manual exposure and
    use realistic values for outdoors
    on a sunny day:

ISO 100

Shutter 100

Aperture 16

  • Adjust the directional light until it is in the exposure range.

This requires around 50000 units on the directional light in order to look remotely correct, but at this point it no longer works with the skysphere, seems to have issues issues with skylight/bounce intensity, clips outside the range for SSR and becomes black, and more.

I’ve included a few images of how this looks when using the above settings in two projects. This is absolutely critical to get working before release, as realistic values for spot and point lights do not work at all with unitless directional. Please let me know if there is something simply wrong with my setup, or if I have missed any answers when digging through github, the forums, issues, and answers.

Thanks!

If you wanted to report a bug you’ve should place this topic under bug reports.