shader_type spatial;

// Cel/toon surface shader used across the game.
//  - Banded (stepped) diffuse with a tinted shadow color instead of black
//  - Soft rim light for silhouette pop
//  - Optional world-space triplanar albedo (level geometry: no UVs needed,
//    grid stays world-scaled) — otherwise standard UV sampling (characters)

uniform vec4 albedo_color : source_color = vec4(1.0);
uniform sampler2D albedo_texture : source_color, filter_linear_mipmap, repeat_enable;
uniform bool has_texture = true;
uniform bool use_triplanar = false;
uniform float triplanar_tile = 2.0;      // world units per texture tile

uniform float band_edge : hint_range(-1.0, 1.0) = 0.05;   // NdotL where light band starts
uniform float band_softness : hint_range(0.001, 0.5) = 0.04;
uniform float mid_band_edge : hint_range(-1.0, 1.0) = 0.55; // second, brighter band
uniform vec4 shadow_color : source_color = vec4(0.62, 0.65, 0.78, 1.0); // cool shadow tint
// Matte-anime defaults: zero specular (any stepped glint reads as shine
// sweeping across hair/cloth when the camera moves), whisper of rim.
uniform float rim_strength : hint_range(0.0, 2.0) = 0.05;
uniform float rim_width : hint_range(0.0, 1.0) = 0.28;
uniform float specular_strength : hint_range(0.0, 1.0) = 0.0;
uniform float specular_shininess : hint_range(1.0, 128.0) = 64.0;

varying vec3 world_pos;
varying vec3 world_normal;

void vertex() {
	world_pos = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xyz;
	world_normal = normalize((MODEL_MATRIX * vec4(NORMAL, 0.0)).xyz);
}

vec3 sample_triplanar(vec3 p, vec3 n) {
	vec3 w = abs(n);
	w = pow(w, vec3(4.0));
	w /= (w.x + w.y + w.z);
	vec2 uv_x = p.zy / triplanar_tile;
	vec2 uv_y = p.xz / triplanar_tile;
	vec2 uv_z = p.xy / triplanar_tile;
	vec3 cx = texture(albedo_texture, uv_x).rgb;
	vec3 cy = texture(albedo_texture, uv_y).rgb;
	vec3 cz = texture(albedo_texture, uv_z).rgb;
	return cx * w.x + cy * w.y + cz * w.z;
}

void fragment() {
	vec3 base = albedo_color.rgb;
	if (has_texture) {
		if (use_triplanar) {
			base *= sample_triplanar(world_pos, world_normal);
		} else {
			base *= texture(albedo_texture, UV).rgb;
		}
	}
	ALBEDO = base;
	ROUGHNESS = 1.0;
	SPECULAR = 0.0;

	// Rim: brighten grazing angles for that inked-silhouette pop.
	float rim = 1.0 - clamp(dot(normalize(VIEW), NORMAL), 0.0, 1.0);
	rim = smoothstep(1.0 - rim_width, 1.0, rim);
	EMISSION = base * rim * rim_strength;
}

void light() {
	float ndotl = dot(NORMAL, LIGHT);
	// Shadowing folds into the band test so shadow edges band too.
	float lit = ndotl * ATTENUATION;
	float band = smoothstep(band_edge - band_softness, band_edge + band_softness, lit);
	float mid = smoothstep(mid_band_edge - band_softness, mid_band_edge + band_softness, lit);
	// 3 tones: shadow tint -> base band (0.82) -> full light.
	float tone = mix(0.82, 1.0, mid);
	vec3 shade = mix(shadow_color.rgb, vec3(tone), band);
	DIFFUSE_LIGHT += ALBEDO * LIGHT_COLOR / PI * shade;

	// Stepped specular dot for glossy toon highlights.
	vec3 h = normalize(VIEW + LIGHT);
	float spec = pow(clamp(dot(NORMAL, h), 0.0, 1.0), specular_shininess);
	spec = smoothstep(0.5 - band_softness, 0.5 + band_softness, spec);
	SPECULAR_LIGHT += LIGHT_COLOR * spec * specular_strength * band;
}