Lighting and GI
The lighting model in Chop Chop is pretty simple, and it relies a lot on the shaders to deliver its look. In short, we bake GI using Subtractive mode mixed lighting and then we process lightmaps with the shader, while realtime objects receive light from Light Probes.
As pictured in the image above, static objects get their shadows baked and approximated by the shader. These shadows are flat and never become fully black. Dynamic objects instead (like the Plant Critter pictured) cast a black shadow on static objects (the ground in this case), but only semi-opaque shadows on static objects lit by light probes (like the little rock, pictured).
The scene setup is extremely simple: we have just one directional light representing the sun and set to Mixed mode. This light has intensity 1 and colour #FFF4D6 (for full day scenes), and is set to provide Soft Shadows.
All big pieces of environement geometry are set to static (Contribute GI), while all small objects (like grass, pebbles, flowers) are set to static but they have Receive Global Illumination set to Light Probes on their MeshRenderer components.
The skybox is a Cubemap skybox material using a custom cubemap which we bake in the scene Scenes/Skybox/ClearSky, using a Reflection Probe placed in the centre of the scene. This scene is not actually used in the game.
For the purpose of baking the sun in the cubemap, we have a fake sun in the sky done using a simple white sphere (seen in the image above).
However, in normal scenes the ambient lighting is provided using a gradient: #B1BFD4 (Sky) #23353F (Equator) #1E241E (Ground).
For baking GI, we use Mixed lighting mode set to Subtractive. Realtime shadow colour doesn't matter, since it's forced to a different colour in the shader.
When we bake lightmaps, much of the nuance of the lightmaps is actually lost because of the toon shader approximating gradients. For this reason, many baking parameters like the number of samples or the lightmap resolution don't make much of a difference.
The only important parameters are the ones as follows:
- We bake Ambient Occlusion and sometimes with Direct Contribution set to 2, to make it stand out a bit more.
- Lightmap resolution is set to very low values, like 10 or even 5 in some big scenes. When making test bakes, we go down to 2.
- Directional mode is set to Non-Directional because we don't need that extra set of maps, given that we don't use a PBR workflow.