Jay Versluis
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Portrait Lighting Test in Unreal Engine: GR Female Demo 427a
🕑 Added 2022-01-21 18:40:34 +0000 UTCThis week I've been busy delving into Unreal Engine and was able to make the above image with it. It's certainly not a master piece, but it shows in principle that portrait lighting can be done, even though the process of getting there is a little difficult. I thought I'd share with you what I've learnt, and perhaps turn it into a feature-length video. It might not look like it, but considerable time has gone into making this picture. Read on to find out all the gory details.
I didn't use a DAZ character because... well that feature doesn't quite work yet with the bridge. Anyone with an expression comes over with eyes popping out and a freak face, so I thought let's stay in Unreal Engine entirely and use a somewhat native character. This GR Female was a freebie a while ago, and she would work fine as my test subject.
The first hurdle I faced was getting Depth of Field going. What we think of as a single click on the default camera isn't for the faint hearted in Unreal Engine. We need a special type of camera actor, then mess with scary settings - but I've managed to make it happen. You can read all about it in my Depth of Field article here.
Lighting is another big deal. Much like DAZ Studio, Unreal Engine has a default HDRI enabled and it's entirely un-obvious how to disable that. Turns out we need to add a Post Process Volume, enable infinite size, switch the exposure control to manual and then add our own preferred compensation value to it - just to see the effects of straight lights we add to the scene manually.
Once that's done, it turns out that adjusting the aperture on the camera inevitably changes the exposure we get piloting the camera (like in real life), so we have a different visual experience depending on what camera we look through. Tricky stuff for previewing, especially if these things catch you by surprise.
Setting up parametric lights can be done as usual, but making them automatically follow an object is not a feature in Unreal Engine. In Blender, there's an option to use the Damped Track constraint to any light. As you move the object, the light follows. DAZ Studio has this feature too, and I rely on it to get the correct visual effect of my lights.
I had to get inventive and essentially write this mechanism from scratch in Unreal Engine.
Here's the problem: the Unreal Editor (i.e. the interface we build things in) does not have the same Event Hooks exposed as when the game is compiled and played. The Tick Event for example is called on every frame that's drawn while the game runs, and you can hook into it so that things would re-caulculate as time passes, like the tracking position of a light in relation to another object. But in the Editor, that event doesn't exist. I can write a Blueprint function to make the light follow my target point, but I can't update it continuously as I move either object due to the missing Tick Event.
Here's how part of the solution looks like to make this happen. I've written an article about how to implement this functionality and made the demo project available on GitHub. Dig in if you want to find out more about this.
Equipped with this mysterious Editor Tick Event, I was able to make the light turn towards a Target Point, which is Unreal Engine's equivalent to an Empty or Null object. If I move either object, the other one auto adjusts.
It makes you appreciate all the logic that's happening under the hood in other 3D applications. Stuff like this is usually not user facing, and it's almost criminal to think that in order to use Unreal Engine for something as simple as setting up portrait lights, you have to write code such as this (and understand what it all means):
I've described the light tracking process in this article if you want to have a crack at it yourself. There may well be easier and more elegant options to achieve this (and by God there bloody should be). As an example, a Camera Actor has tracking logic built in and it works just fine in the editor. Unreal Engine is improved all the time, and I have a feeling that there's a yet to be discovered mechanism I could be using instead of my approach.
Did I mention rendering a picture out? Yeah that's... not a single button click either. You can use a High-Res screenshot, which is as close to "one-click" as it gets, or you can install a plug-in called the Movie Render Queue and render a one-frame animation of your scene. This involves creating Level Sequence, getting comfortable with the Sequencer, doing some tests and finally ending up with a high-res image. I've described parts of the process in this article, which focusses on the Movie Render Queue. I'm looking forward to exploring a related plug-in for multi-pass rendering soon.
In conclusion: Yes, Unreal Engine can do it all - and render times are staggeringly fast. The setup to get us there... not so much. The sheer knowledge and understanding you need to bring to make a mediocre render like the above come out is mind blowing. To make Unreal Engine work as a render horse equivalent to DAZ Studio or Blender takes a serious learning curve, and even then it's not at all user friendly.
While I appreciate that the editor is designed the way it is to bring anything from level building, game logic and project building together, it's complete overkill if you want to render still images. I feel like there should be a whole different type of editor for 3D artists that hides most of the settings, something like a completely different front-end editor. If it doesn't' exist yet, I'm sure others have thought about writing one already. I've read that Unity game devs have similar issues, and custom made editor interfaces seem to be commonplace.
On a related note, Julia is currently heavily involved in a project called Core, which is a game engine built on top of Unreal Engine. They've essentially done what I've described for casual game builders: do away with the Unreal Engine editor, create their own interface and even tie it together with a scripting language (Lua) that's not available in Unreal Engine. It aims to make game development easier, while still using all the good things of Unreal Engine and stripping the away the overkill. They got a Mega Grant from EPIC for this idea.
Maybe one day we'll get this for 3D stills? Until then, it's takes several hours to setup a render like the above. I'll let you know if I can find a way to make this easier, and make it work with DAZ characters at some point. Watch this space!
