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Procedural skies vs Hdri. What´s your lighting workflow?

Hi there,

I spent the last week or so diving into unreal so I am still quite new to it. I love it but I realized it is indeed a game engine, and as obvious as that might sound, I also realized that may be important to try and learn the engine natural way of doing stuff, rather than taking our regular archviz workflow on other engines and trying to reproduce it on UE.

That said, I almost became crazy trying to understand the hdri lighting, which is **** easy to set up in whichever engine you are used to (me that´d be corona, vray at first).
Right to this moment what I got is this for hdri lighting on UE:

  1. Use a skylight and a .hdr on the “skylight specified cubemap”. Okay, that´s easy enought.
  2. Get a huge sphere and drop a material into it. This material will be set to unlit and you will use a “TextureSampleParameterCube” to insert your hdr texture there and a “reflection vector” with a “constant 3 vector” attached so it won´t give you an error. I have no idea as to why do I need those last slots but well, for the moment it´s working, so that´s fine. I would like to understand that though.

I think that is physically correct and works just fine, but it´s not really enought. The background obtained this way is kind of wash out and should look more like what this tut shows https://80.lv/articles/understanding-lighting-creation-in-games/, but I found impossible to get that result without my sun getting black artifacts and odd things. Then it´s always the problem with the shadows when using hdri. It pretty much depends on your maps but I could not get any aceptable shadow out of Peter Guthrie´s maps and I think everyone is using a sunlight attached to their background.

So summarizing, the part of hdri lighting regarding lighting itself I found it really easy to set up within UE via a skylight specified cubemap.
Then the part regarding background and shadows, that´s another story. I found tutorials (some really confusing ones) and several methods, more like workarounds for something UE is not that much into. That was my impression. Is this as I stated? Do you guys feel that way too or it´s just me?

All that leads me to procedural skies for our scenes, because it is the way UE seems to want us to create atmosphere with. The main question here is for me, could we forget about hdri lighting if we master the integrated tools for procedural skies? I think I would love to.
Setting up the mood of your scene with your sky and using a skylight to catch the light and reflection would be as physically correct and hi quality as using hdri lighting?
Could this two mix (using hdri on skylight, sunlight for shadows, and procedural skies as background only)?
I found a plugin TrueSky that looks fantastic, and I don´t think I need better backgrounds than those of the reel.

What are your thoughts on this matter?
I also thought it could be nice and useful if we all wrote here our workflows as a list like I did atop this, so feel free to do so :wink:

Hope this topic is of some interest.

I’m new to Unreal as well, although moved from Unity; not a coder but an artist. But I would really like to understand and implement procedural skies as well. Unless I’m missing something, there doesn’t seem much on it, or any tools that are aimed at a more straightforward creation of them. I have done the above flow of the HDR, and that works OK, but procedural would be so much more useful, and powerful.

  • Get the ultra dynamic sky from the marketplace. It will be a great starting point.
  • I use a hdr in the skylight. Don’t forget to rotate it.
  • use a post process volume and put a LUT into it. There are a few LUTs in the engine content folder which is hidden by default.
  • tweak the exposure bias and the exposure min max settings. Defaults are working great for games but need tweaking for Arch Viz
  • I find textures a bit too saturated. You can reduce this among lots of other things in the post process volumes. You can place multiple volumes with different priorities. They are camera based so you need to be inside the volume to see the effect.
  • You need reflection actors or everything looks slightly blue
  • Add a lightmass importance volume to cover the main area. This improves quality and reduces built time.
  • Use a stationary sun directional light and set the dynamic shadow distance to maybe 1000 units (max).
  • add light portals into window openings.
  • build lighting. Preview is a quick first test but gives you a good first picture of what production might look like and points at obvious errors.

There are tutorials on this site for each of these items. Hope that helps to get started. Generally the skylight can’t really be the only light source. It’s getting better with multi bounce skylights but it is not the same as in 3ds max.

@S-Dot the items you describe are all based on ultra dynamic sky? for example point 2 are you referring to the skylight actor for the ultra dynamic sky?

I come from octane render…and one thing I LOVE is that we can use HDRI very easily not just to light our scenes…but also to cast shadows…I’ve never been able to achieve shadow casting with an HDRI in ue4…I always have to use directionallight to do that :(.

A good HDRI and postprocess do the trick…

Not all items, only the ones that are part of ultra dyn. sky. The other actors need to be added. As far as I know the skylight in unreal does not cast any shadows.

…from the Unreal documentation:
https://docs.unrealengine.com/latest/images/Support/Builds/ReleaseNotes/4_18/image_4.gif