shader_type spatial;
render_mode blend_mix, depth_draw_opaque, cull_back, diffuse_burley, specular_schlick_ggx;

uniform vec2 wind_direction = vec2(0.94, 0.34);
uniform float wind_strength : hint_range(0.0, 0.2) = 0.07;
uniform float wind_speed : hint_range(0.0, 2.0) = 0.55;
uniform float gust_speed : hint_range(0.0, 1.0) = 0.12;
uniform float gust_strength : hint_range(0.0, 0.8) = 0.35;
uniform float flutter_strength : hint_range(0.0, 0.05) = 0.012;
uniform float wind_phase : hint_range(0.0, 6.2832) = 0.0;
uniform vec3 albedo : source_color = vec3(0.19, 0.38, 0.17);
uniform float roughness : hint_range(0.0, 1.0) = 0.9;

void vertex() {
	float half_height = 1.2;
	float height_factor = clamp((VERTEX.y + half_height) / (half_height * 2.0), 0.0, 1.0);
	height_factor = height_factor * height_factor;

	vec2 direction = normalize(wind_direction);
	vec2 crosswind = vec2(-direction.y, direction.x);
	float world_phase = wind_phase + dot(MODEL_MATRIX[3].xz, vec2(0.07, 0.05));
	float gust_wave = 0.5 + 0.5 * sin(TIME * gust_speed + world_phase * 0.7);
	float gust = mix(1.0 - gust_strength, 1.0, gust_wave);
	float bend = sin(TIME * wind_speed + world_phase) * wind_strength * gust;
	float flutter = sin(TIME * 1.7 + world_phase * 1.9 + VERTEX.y * 2.0) * flutter_strength;

	VERTEX.xz += direction * bend * height_factor;
	VERTEX.xz += crosswind * flutter * height_factor;
}

void fragment() {
	ALBEDO = albedo;
	ROUGHNESS = roughness;
}