shader_type spatial;
render_mode diffuse_burley, specular_schlick_ggx, cull_disabled;
// Luneraria CLOTH: team banners and pennants. The mesh is a plain rectangle (UV v = 0 at the
// pole, 1 at the hem); silhouette and emblem come from the team: shape 0 is the cool team's
// swallowtail with a crescent, shape 1 the warm team's flame-tongue hem with a sun disc.
// Wind waves grow towards the hem; `tatter` tears holes for damaged buildings.

uniform float wind_strength = .12;
uniform float wind_speed = 1.6;

instance uniform vec4 cloth_color : source_color, instance_index(12) = vec4(.2, .4, .8, 1.0);
instance uniform vec4 emblem_color : source_color, instance_index(13) = vec4(.92, .9, .8, 1.0);
instance uniform float shape : instance_index(14) = 0.0;
instance uniform float tatter : instance_index(15) = 0.0;
instance uniform float fade : instance_index(1) = 0.0;
instance uniform float fade_floor : instance_index(2) = 2.2;
instance uniform float seed : instance_index(3) = 0.0;

varying vec3 world_pos;

#include "res://scripts/luneraria/view/materials/lune_common.gdshaderinc"

void vertex() {
	float hang = UV.y;
	float t = TIME * wind_speed + seed * 3.0;
	float wave = sin(t + UV.y * 4.0 + UV.x * 1.5) * .6 + sin(t * 1.7 + UV.y * 7.0) * .4;
	VERTEX += NORMAL * wave * wind_strength * hang * hang;
	VERTEX.y += cos(t * .8 + UV.x * 2.0) * .02 * hang;
	world_pos = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xyz;
}

void fragment() {
	if (PROJECTION_MATRIX[3][3] < .5 && faded(fade, fade_floor, world_pos.y, FRAGCOORD.xy)) discard;
	vec2 uv = UV;
	// Team silhouette.
	if (shape < .5) {
		// Swallowtail: a V cut from the hem.
		float cut = .72 + .28 * abs(uv.x - .5) * 2.0;
		if (uv.y > cut) discard;
	} else {
		// Three flame tongues.
		float tongues = .8 + .2 * pow(max(0.0, cos((uv.x - .5) * 3.0 * 6.28318)), 2.0) - .05 * abs(uv.x - .5);
		if (uv.y > tongues) discard;
	}
	if (tatter > .01 && noise3(vec3(uv * vec2(9.0, 14.0), seed)) < tatter * .45 * smoothstep(.3, 1.0, uv.y)) discard;
	vec2 e = (uv - vec2(.5, .38)) * vec2(1.0, 1.35);
	float emblem;
	if (shape < .5) {
		// Crescent moon: a disc minus an offset disc, and a small star.
		float outer = length(e) - .2;
		float inner = length(e - vec2(.09, .04)) - .17;
		emblem = step(max(outer, -inner), 0.0);
		emblem = max(emblem, step(length(e - vec2(.12, -.12)), .03));
	} else {
		// Sun: disc and rays.
		float a = atan(e.y, e.x);
		float r = length(e);
		emblem = step(r, .11);
		emblem = max(emblem, step(r, .2 + .05 * step(0.0, cos(a * 8.0))) * step(.14, r));
	}
	float trim = step(uv.y, .06) + step(abs(uv.x - .5), .5) * (step(.46, abs(uv.x - .5)));
	vec3 color = mix(cloth_color.rgb, emblem_color.rgb, clamp(emblem + trim * .8, 0.0, 1.0));
	float weave = noise3(vec3(uv * vec2(80.0, 120.0), seed)) * .08;
	ALBEDO = color * (.92 + weave) * (1.0 - tatter * .25);
	ROUGHNESS = .88;
	BACKLIGHT = color * .35;
}