Joey Lenz gave a detailed talk on lighting in UE4: values, sources, light temperature, lighting in PBR pieces, sources to learn lighting and more.
I remember very clearly what first inspired me at a young age. I was around 5 when my parents bought me a SNES for Christmas. One of the games that came with it was Super Mario World. And boy, was I ecstatic to unwrap that one! My “eureka” moment occurred during the first level when I had Mario jump and hit a question mark box. Yoshi popped out, and I was completely blown away. I became fascinated with how the interactive mechanics worked, even though I had no clue at the time. And so, my interest in games, beyond just playing them, began with Yoshi changing my life.
My digital art career started with me doing some graphic design and visual effects. I worked a few smaller gigs and independent films, but my career in games took off on a whim from my best friend, Phil Liu. He was studying game design at the time and suggested I try learning the Unreal Engine 3. It wasn’t long before I fell in love with real-time artwork and the level of interactivity provided. What I found to be the perfect combination was that I could take the cinematic visual fidelity of film and optimize it for run-time utilization in an in-the-round, digital environment. Since those days, I’ve worked on various game series, like Call of Duty, Halo, Forza Motorsport, etc.
PBR, or physically-based rendering, provides a convenient means of authoring materials/lighting with predictable, consistent results under varying lighting conditions by using measured, real-world data. What this means for studios is that their artists can spend less time iterating on content and reworking it to look “correct” for different levels. In turn, this saves studios money. PBR can take a little time to get used to for artists, who come from working with older methodologies. Sometimes their biggest challenge can be getting comfortable with not adding lighting/shading information to albedo textures. However, once they become familiar with this workflow, they soon realize it can be easier to manage than more traditional means of rendering textures.
This is my latest, personal PBR piece I collaboratively worked on with Phil Liu: The Game of Thrones Iron Throne. He modeled/textured it all in Substance Designer, and I was responsible for the lighting/post in Marmoset Toolbag 3. You can learn more about this project by visiting my portfolio website.
One thing I strongly believe in is that PBR should be treated as a guide and not the “be-all, end-all” solution for every circumstance and game. It’s part of an artist’s tool palette and not a replacement for creativity. At the end of the day, we’re here to visually tell a story, which means we need to sometimes take artistic liberties to evoke particular emotional responses from our audience and players.
Lighting Scenes with PBR
Using the PBR workflow creates a consistent and predictable standard for lighting and authoring of materials. For instance, by keeping albedo textures within a recommended luminance range, means assets won’t appear too dark to light properly or look unusually bright compared to other elements within the environment. Bounce light plays a major role in this part of the process. If your base colors are too dark, textures can then absorb more of the light’s energy instead of reflecting it, thus potentially flattening the space. On the other hand, albedo values that are too bright may reflect too much indirect light, creating areas that are brighter than necessary. This same concept can hold true for saturation levels. For example, if an object’s textures are too saturated, it can bake with lighting results that are less than desired and are too saturated. While maintaining values within certain ranges can be used to achieve photorealistic results, it also helps keep the overall scene balanced, that objects are relative and feel like they live in the same universe. However, if you’re trying to create a specific look or focal point, sometimes breaking PBR guidelines is the best way to accomplish the intended effect.
Below is a sample of UE4 albedo luminance ranges found on my portfolio website’s PBR Guide section.
Below is another sample but of UE4 albedo saturation percent values found on my portfolio website’s PBR Guide section.
Many artists are used to working with RGB values to define color, but color temperature takes a different approach with Kelvin units. This process is primarily used to describe natural light source colors. One example of this can be observed with our sun, which has a different color temperature depending on the time of day. It’s warmer during sunrise/sunset and is more neutral around noon. So, if an artist needs physically-accurate light color values, color temperature provides a convenient means for this. Additionally, some man-made lightbulbs artificially use color temperature, which can be useful to know if you’re trying to mimic particular ones for your scene.
Below is a sample of color temperature values found on my portfolio website’s PBR Guide section.
Applying physical light units and values can help quickly achieve photorealistic results. Though, even when I’m using PBR standards, I like to do an artistic pass afterward. More specifically, I like to use PBR values as a base in UE4, but then I like to occasionally build upon them to enhance the look and feel of my projects. For instance, I use lux values for sun intensities, cd/m² for skies/emissive textures, and lumen/candelas for man-made light sources. I’ll even sometimes research real-world values to apply to UE4 lights, but then I may adjust their intensities/colors if it gives me a greater visual impact. Or, I may strictly rely on real-world values and then modify the look once I start color grading (whether directly in UE4 or through some 3rd-party application, like Nuke, Photoshop, or Davinci Resolve) and tweaking post effects. There are countless ways to go about it and it really depends on the user’s artistic preferences.
Lookup tables, or LUTs, can be used to color grade a scene. Other methods for color grading can include color wheels/curves, which can render more accurate results.
Some artists only rely on a sun/sky setup, but lighting can be much more enriching than that. For me, if it’s an exterior shot, I use the sun and sky as a base (this can also vary depending on the time of day, weather, etc.). Given, if I’m working on a particular type of game, this may be all we can afford due to technical limitations on performance. If that’s not the case, I’m a fan of using fill/helper lights to create focal points, areas of interest, layering of background-to-foreground elements, increased visibility/bounce in local spaces, a method to guide players in a particular direction, render a specific mood/atmosphere, gradients/color contrast to convey form, etc. It doesn’t end there, lighting can also be utilized for cookies (in UE4, they’re called “light functions”), dappled/reflected lighting, visual effects, and much more. While some of these methods may not be physically-based, they are designed to enhance the look and player experience.
This is a UE4 light’s light function parameters:
Interior lighting, on the other hand, can take a bit of a different approach. I’m a fan of using portal lights on windows and other interior openings to the outside world. This allows for better skylight directionality to fill the interior area than, say, if you were to use a spot/rect light instead. Not to mention portal lights can yield higher-quality bakes and reduce visual noise within lightmaps (in UE4, Lightmass Importance Volumes can help with this, too). Moreover, I may even add supplementary fill/helper lights with a softer falloff so additional light can enter further into the interior environment. These lights may include more saturation and a possible color shift, simulating color temperature changes based on falloff distances, when compared to their portal light counterparts. This, I feel, creates better form and enriches the space.
This is a UE4 portal light, which can be accessed in the Modes section:
There’s a window offscreen, allowing light to enter the room. The only difference between the two images is whether it’s using a UE4 portal light near the window or none at all.
Unnatural Lighting for Buttons & Other Elements
A lot of smaller details, like buttons, use glowy textures called emissive maps. These can be used during the baking process to emit light into the scene. What’s nice about this technique is the emitted light is based on the texture and the location of those pixels relative to world space coordinates. This allows for better subtlety and more accurate results than by using, for example, a point/spot/rect light to simulate light coming from the button. To further control the emitted light intensities, I’d adjust the emissive texture’s strength. In UE4, this can easily be done in the Material Editor (by multiplying an emissive texture against a value) or by adjusting a static mesh’s (that has been assigned an emissive material) Emissive Boast parameter. Cd/m² values can be applied to emissive textures.
This is a UE4 emissive material example and the different ways you can adjust its emissive strength:
Disabling/enabling a static mesh’s ability to emit static lighting:
When dealing with more abstract light sources, like magical portals or sci-fi elements, you can apply several methodologies to them. Sometimes just eyeballing them is good enough. However, if you do that, and if these lights/effects are used across several levels, they may not hold up with the same level of expected consistency. So, another technique, which I prefer, is to compare those light effects’ values to established PBR ones. Even if they don’t use pre-defined, real-world values, it’s at least a way to balance and compare them against so they can harmoniously exist in the believable worlds they are in. Trying to establish baseline standards, even for more fantastic lighting elements, reduces the time it takes to rework them, as well as the rest of the art.
Advice for Learners
There are plenty of online resources to learn more about lighting these days. My best advice is to not limit yourself to just UE4. Learn from as many different mediums as possible. Study cinematography, stage lighting, games, classical paintings, photography, how theme parks light their resorts, talk to/learn from professional lighting artists, concept art, comic books, nature, etc. (in my opinion, nature is the best teacher of them all for art). Learn art fundamentals first, because while understanding how tools work is important, they alone do not make pretty pictures and are always changing.
For good, online lighting materials, research into Jeremy Vickery’s Gnomon Workshop tutorials. And for UE4 lighting specifically, Tilmann Milde has a great Lighting Academy YouTube series. Finally, if you’re looking for UE4 PBR material/lighting guides, I have an entire section on my website dedicated to just that. I’m always trying to update it and you can read about it here.
Joey Lenz, Senior Level Lighting Artist at Naughty Dog
Interview conducted by Kirill Tokarev
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