Oatvercast Blog

This is part 1 of 'Lustrous Learnings', a series of posts about Lustrous Spirit which is a game I've spent the last four years making. Lustrous Learnings focuses on game development concepts I've stumbled into which aren't often discussed.

Harnessing Light in your Game - Lustrous Learnings

Using advanced lighting tech in your game can be fun, eg pretty bounce lighting, ambient occlusion, etc. A nice render engine can quickly make your 3d game look pretty. As a current Unreal developer I appreciate what Lumen does for my indoor scenes without having to learn to bake light myself (maybe one day...) however often it could not meet my desires while trying to imitate the sparkly, bright, and colorful style of Land of the Lustrous, the anime Lustrous Spirit is based on.

In Land of the Lustrous there are seldom black shadows, foliage is vibrant and interiors are illuminated. Lighting is super important too, and is largely affected by the weather and time of day. Sunset scenes are washed in orange, daytime is vibrant, and night is a cool blue. There is a very particular quality to the light and my goal was to recreate it dynamically in a game engine. Could the default engine settings cut it?

Default unreal settings were not enough to achieve the Lustrous look. blah blah blah there were differences in aesthetic, but the point is I needed a way to control lighting on different objects without having to tinker with post process and other rendering settings that would affect everything. I wanted a way to make light affect different objects differently, so that I could make foliage translucency look like it does particularly in HnK, make gems glow in the light the way they do in HnK, and give various environmental elements the light qualities that appear in concept art. What I needed was control over how light affected each object in a way that PBR materials can't provide.

Global Sources of Light

To make this lighting stuff work I created several lighting variables for any script or material to access - most importantly 'direct light' and 'ambient light'. These control the color and intensity of the direct and ambient lights in the scene, and can be accessed by any materials or effects that wish to take these lighting values and amp them up in one way or another.

Lustrous Spirit's lighting and atmosphere management script takes the time of day as input and sets variable like fog density, the sun disk's position, and of course the direct and ambient light color variables. Day cycle is a whole nother can of worms which I might get into in another article, but point is we're controlling light color and intensity directly through a manager script and that's how we get the global source of truth for lighting - scripts and materials can ask the lighting manager what the lighting is like.

To easily let unreal materials get these lighting variables, I use material parameter collections and material functions. Material parameter collections are sets of parameters that any material can access, so the lighting manager sets direct and ambient light color in a lighting material parameter collection. Then I create material functions for common lighting-based effects which access the material parameter collections. For example, since Land of the Lustrous avoids black shadows (which commonly occur with unreal's renderer), I boost material brightness by adding a portion of the ambient light into materials' emissive channel. This is such a common occurrence that I created a 'boostLighting' function that I apply to outdoor objects' materials.

If I were a graphics programmer I would probably write this whole system more optimally onto the GPU, but for us less technically inclined gamemakers this lighting control system gives some stylistic lighting control over a typically PBR-focused engine. I was able to both have global illumination for nicer interiors while having nice colorful shadows.

Applications

Critiques

Honestly while writing this I feel like this approach is really friggin flawed. If you want a very particular lighting look in a game, you should really do a bit of graphics programming and work with an engine that will let you build lighting from the ground up rather than diving into the deep end haphazardly running into engine features. If I were to make lustrous spirit again would I do it in Unreal? It's hard for me to imagine it in a different engine knowing how much it was shaped by Unreal's tools, but let's just consider it graphically for now - if I were to make another game imitating the Land of the Lustrous style, would I make it in Unreal? Honestly... probably not. As much as using engine renderers can shortcut you towards a look, where they place you may have tougher obstacles to getting your ideal look than just starting from scratch (or more accurately, from an engine that doesn't enforce as much style).

tbh i might not publish this article cuz although lustrous lighting has been a great learning experience for me, i think it serves better as a cautionary tale than an instruction manual for others LOL like tbh I do not want to send other people down this rabbit hole. dickin around in Unreal has taught me a lot but it did not lead to an ideal way of creating visual style or handling lighting. if anything the lessons here are 'how do you negotiate an engine's powerful graphical tools when they don't do exactly what you want?' which is certainly a valid way of developing independent games but is not a good way of doing lighting which I was originally positing this post as.

Anyway im glad to have wrote this. point is, render engines have default looks to them, sometimes you have an established look which doesn't match the engine, and to reach it you need to understand both the engine's nuances and the nuances of the style you are trying to achieve to get from one to the other. and unreal? its got a lotta fuckin nuances.