For my reference, I took inspiration from various pieces of kingdom hearts cover art. These all have a similar water color painted style with pencil outlines. In particular the image I referenced most was:
I believe this art was created by Tetsuya Nomura, but I wasn't able to tell if that was truly the case. It is a booklet that was given out to people who pre-ordered KH 2 Final Mix +.
For adding multiple light support, I made some modifications to the helper code in order to both discretize the additional light diffuse values, as well as the main light diffuse values. I ended up using the sum of both light values in my output shader for diffuse + specular, and utilized just the main light shadow for textured shadows since I thought it got a bit too messy otherwise.
As mentioned, I added a specular highlight to the main light source, since it gave the scene a bit more color depth compared to just 3 tone shaders, while still getting a discretized shading look.
For my shadow, I ended up actually pulling out a sketchbook and a graphite block to just rub over the surface to get the texture of the sketchbook paper to reveal in a texture. This is what the final tiled texture looked like:
In my final scene, this texture is less aparent since I have a painterly effect plastered on top, but in a raw scene it looked something like this:
For my surface shader, I decided to both add a hue shifting effect as well as a kuwahara filter since my hue shift didn't have a lot of complexity or used many toolbox functions. For my hue shift I used a sine wave over time to shift hues up and down by a customizable parameter magnitude and speed. I made this effect have a very high magnitude on the popsicles to make them pop out of the scene which I think is a fun touch.
For the kuwahara filter, I implemented this as a post process effect. The general idea of a kuwahara filter is to divide a pixels suroundings into 4 quadrants, and assign that pixel with the average of the quadrant with the lowest variance. This creates streaks in the output that kind of look like paint strokes. Note that I did this effect before applying outlines to ensure outlines still stay sharp.
I opted to mix some of the outline techniques together, since I found the best effect with sobel kernels, but wanted to also use my normal buffer for them. I do have support for outlines based on color, but for my final product I chose to have stationary outlines based on normals, and wiggling outlines based on depth information.
I made the depth outlines wiggle by applying a gradient noise to the central UV coordinate when sampling depth values which scrolls over time, but has a floor function applied to time so it isn't constantly moving.
Apart from the kuwahara filter, I also implemented a white vignette since my reference image kind of fades into white around the edges. I also added a bit of noise to the vignette so it wasn't super harsh and made the image look more worn in.
In my main scene, I set up spongebob and squidward chilling out eating a popsicle similar to sora and roxas in the cover art I took as inspiration.
The squidward model is made by 3D by Renato on Sketchfab under the CC license. Model: https://sketchfab.com/3d-models/squidward-spongebob-7b35d58ae22d480a9d365ccda411b086. CC License: https://creativecommons.org/licenses/by/4.0/
The spongegbob model is by Gummibar gumy bear on Sketchfab under the CC license. Model: https://sketchfab.com/3d-models/hip-hop-dancing-spongebob-16f1c72703974d35957eeeabb4ff3d32. CC License: https://creativecommons.org/licenses/by/4.0/
And finally the popsicle model is by ZREEL on Sketchfab under the CC License. Model: https://sketchfab.com/3d-models/popsicle-ice-cream-isometric-c34b893d6e7c4267abad4b4fc79ff01a CC License: https://creativecommons.org/licenses/by/4.0/
As an addition, I also used a model of a granny for testing which is still in the project files from mixamo: https://www.mixamo.com/#/?page=1&query=Sporty+Granny&type=Character
For my interactive mode, I implemented a "CRT" mode that mimics a glitchy CRT monitor. This can be toggled by pressing "C" on your keyboard when playing. It causes there to be a blur with moving scanlines and chromatic aberration, as well as occasional glitches I implemented by picking random movement vectors and thresholding a white noise function that scrolled over time.
(This is from Videos/PlainScene.mp4, just re-uploading so it shows in preview mode) https://github.com/user-attachments/assets/a6ac52d4-e797-43c0-9aab-1f63208d87b5
(This is from Videos/CRTScene.mp4, just re-uploading so it shows in preview mode) https://github.com/user-attachments/assets/e50fd278-b6df-41a0-b40a-94ea052721ea