grunk/src/shaders/gunk/gunk_overlay.gdshader

shader_type spatial;
render_mode depth_prepass_alpha;

#include "common.gdshaderinc"

group_uniforms gunk_mask;
uniform float edge_bleed = 0.25;
uniform sampler2D gunk_mask;


float bump_sample(vec2 uv, vec3 uvt, float dx, float dy) {
	vec2 offset = vec2(dx / pixellation, dy / pixellation);
	float height = texture(gunk_noise, uvt + vec3(offset, 0.0)).r;
	float mask = texture(gunk_mask, uv + offset / uv_scale).r;
	return height * smoothstep(1.0, 0.0, mask);
}

void fragment() {
	vec3 uvt = scale_uvt(UV, TIME);
	float value = sample_noise(uvt);
	ALBEDO = base_albedo(UV, value);
	ROUGHNESS = base_roughness(value);
	EMISSION = base_emission(UV, value);
	SPECULAR = base_specular();

	// Build normal map from bump map
	float h_center = bump_sample(UV, uvt, 0.0, 0.0);
	float h_right = bump_sample(UV, uvt, 1.0, 0.0);
	float h_down = bump_sample(UV, uvt, 0.0, 1.0);
	float dx = (h_center - h_right) * bump_strength;
	float dy = (h_center - h_down) * bump_strength;
	vec3 normal_diff_map = normalize(vec3(dx, dy, 1.0));
	NORMAL_MAP = normal_diff_map / 2.0 + 0.5;

	// add fresnel
	vec3 world_normal = mat3(TANGENT, BINORMAL, NORMAL) * normal_diff_map;
	EMISSION += rim_glow(
		world_normal,
		VIEW,
		fresnel_gradient,
		fresnel_color,
		fresnel_power,
		fresnel_intensity
	);

	// add iridescence
	ALBEDO += rim_glow(
		world_normal,
		VIEW,
		iridescence_gradient,
		iridescence_color,
		iridescence_power,
		iridescence_intensity
	);

	// Hardish edge
	float mask = texture(gunk_mask, UV).r;
	ALPHA = hardstep(1.0 - mask + edge_bleed);
}