Breakdown
- Basic idea is to discretize (remove transitions).
- We do this by calculating light intensity to be a fixed constant if the surface is pointing towards light, else it is zero. This is unlike a smooth transition that occurs in lambert or other shading models.
- The diffuse light is added first.
- Then specular light (just by varying some values)
- Finally, we add rim light, which depends on dot product of view angle and the surface normal.
Godot Code
shader_type spatial;
uniform vec3 color: source_color;
// Cel shader
void light() {
float diffuse_intensity = dot(NORMAL, LIGHT) > 0.5 ? 1.0 : 0.0;
DIFFUSE_LIGHT = diffuse_intensity == 0.0 ? color / 2.0 : color;
float specular_intensity = dot(NORMAL, LIGHT) > 0.990 ? 1.0 : 0.0;
SPECULAR_LIGHT = color * 2.0 * specular_intensity;
float rim_dot_product = 1.0 - dot(VIEW, NORMAL);
float rim_intensity = pow(smoothstep(0.0, 2.0, rim_dot_product) * 2.0, 4);
DIFFUSE_LIGHT += rim_intensity;
}This post is incomplete.