Lighting: From Concept to Render

What is lighting? Is it the process of putting lights into an otherwise dark scenery to reveal the set and the characters? Guiding the viewer's eye to enhance and communicate the story? What if you're not putting in lights, but instead you are tweaking values, colors, adding elements to the scene, overlaying things in compositing... doing anything to form the final image in support of the director's and art director's vision - is it still lighting?

If this all sounds a bit strange and pretentious, please hear me out: Much of my job in the past has been described as "lighting". That's the task I see when I consult Kitsu which shot I'm supposed to work on today. And yet, I've found that putting in lights and tweaking them is about 20% of the job. What happens around that feels more like tweaking an enormous amount of numbers in a spread sheet.

In Wing It!, much of the lighting magic happened in the shading setups which Simon has already explained in great detail. There isn't much to add, the rest was handled by very basic environment light setups with some compositing on top. Achieving the final look pretty much amounts to just tweaking all the numbers until it looks right. I found that a lot of the day-to-day work was boiling down the essence of the concept art or color script and finding a matching look through all the parameters at our disposal. So let's break this process down!

We'll be using the shot 020_0040_A as an example, check out the production file if you want to follow along.

Process breakdown

Starting from a blank slate is always difficult, it's a good idea to have a clear goal in mind where you need to go. That can be a photo reference, or a concept art piece. A color script tells you about about the overall continuity and the context your current shot is in: Where are we in the story? How does the mood progress over the course of a sequence?

The absolute best reference to have is key artwork for individual shots. However, most of the time that is very time-consuming to achieve in a small production like ours. In the last couple of projects we've established the workflow of doing a very quick pre-lighting of the animation blocking, turning that over to the concept art department for a paint over and then adjusting the work based on that. With this workflow, concept art already has a framework to maintain continuity and the lighting does not start from a complete blank slate.

When we have concept art to work from, dissect it into small bits and pieces and finding out how to implement them through the shot parameters is the next step. On Wing It! we analysed the initial concept art and broke it down into parameters that could be exposed and replicated in each shot.

After the animation for each shot was blocked, Beau and I could already start doing a quick lighting pass of the scene which we turned over to Vivien for detailed feedback. In most cases we took the following steps.

The base color tint

It's always a good idea to have a base environment light to work from, so you are (literally) not starting out completely in the dark. Since Wing It! was based more in the NPR realm, we added a simple base color tint which was defined in the color script. To propagate this into all the shots, we set up a bunch of World environments, one for each major sequence. Since quite a lot of shots were set in the barn, I made a preset light setup for that environment which could be linked into all the interior shots. Together, these would give the scene already a base to start from.

Global key lights

With the concept art and color script as reference, I prefer to define the key light directions first since that influences the shot continuity the most. In Wing It! the environments were lit almost entirely separate from the characters. A simple sun was sufficient for the environment keys.

Character key lights

The character assets themselves had their own separate shading controls. While they would still be subtly influenced by the environment lights, we could also completely decouple them. The global key lights were used as an indication to set the character keys. In terms of controls we could adjust color highlights and shadows, a Tilt property serves as the means to control the angle of the light. We had precise control over the shadow and highlight color of the characters.

Character rim lights

There was almost always some kind of rim light on the characters to lift them off the backgrounds. The lighting rigs exposed two separate rims we could color and intensify at will. We could choose to put them opposite the keys or with them. Sometimes the main shading controls were used in place of the rim as well (in extreme back-lit situations).

Environment accent lighting

After the light direction was established, additional accents were added to highlight parts of the environment to further stylize the image and create additional interest. These could be area-, spot- or point-lights.

Shadow placement

We decided to simplify the shadows a lot. The sun key light was generally the only source that would cast a shadow. Most of the props and set elements were already excluded from shadow casting from the get-go to keep the overall look simplified and cartoony. The characters had special shadow proxy setups to cast simplified shadows with controllable gradients onto the backgrounds.

Separating View Layers

We separated the scene into individual View Layers. Base contains the beauty pass of the foreground of the shot. Outlines used the whole scene geometry as Holdout to give us a clean layer of all the line work. All the animation smears were put on the Grease Pencil layer. To give us a better way to tweak and light the shots, there was a Preview View Layer that would be excluded from final rendering. This setup was mostly handled by the shot builder. It took care of separating the scene collections into their own View Layers and linked them together in the compositor.

Outline color adjustments

Each object that would generate an outline had a modifier to give us individual control over the generated outline color. With this we had extremely fine control to override the existing colors per shot if necessary.

Outline lighting

To create more fidelity in the outlines, we decided very early on to move them to a separate render pass in order to have more control over their lighting. This allowed us to place extra highlights on the edges of certain background elements to give them a stylized look.

Compositing

We made Node Groups that could combine all the output passes of individual render layers together. There was one for the beauty pass and one for the outlines. After this stage, we could merge the outlines with the background. Both of them had a depth color gradient which let us fade in a uniform color to create better character separation. The gradient was linked together for beauty pass and outlines but could be split for more freedom. Compositing was so integral to the final look of the shot that it happened directly in the lighting files.

Feedback and Paint-over

Following this process made it quite fast to turn over a quick render to the concept art department for feedback and paint-over.

Having people who know what they are doing in 2D is an enormous asset to get good feedback. When you are in a 3D scene you can often get carried away with all the options. The result is often way too detailed. A 2D mindset helps to break down the image into its essence.

Tweaking and fine-tuning

From this point on, it's basically rinse and repeat. When you have completed enough shots, this process generally speeds up. Specific sets of values can be transferred into other shots, thus after a while they become second nature.

So... is it lighting?

Whatever you might call that process is not really important, what it comes down to is that it's all about flexible iteration, analyzing your work and collaborating with your team mates. Wing It! was extremely rewarding in all these points. In the end, I was super happy we managed to give each shot a lot of care and attention.

I hope this little breakdown has given you some insight into the thought process behind the lighting in Wing It! and maybe for NPR in general. As our next productions are certainly going to be less on the photorealism side, this project was a valuable exercise.