grunk/src/shaders/gunk.gdshader

shader_type spatial;
render_mode cull_back;

uniform vec4 color_1: source_color = vec4(0.0, 0.03, 0.1, 1.0);
uniform vec4 color_2: source_color = vec4(0.0, 0.1, 0.3, 1.0);
uniform float roughness: hint_range(0.0, 1.0) = 0.15;
uniform float specular_contribution = 0.2;

// Used ONLY by the gunk, does not affect the gunk mask.
uniform vec2 uv_scale = vec2(1.0);

uniform float edge_bleed = 0.1;

uniform sampler2D gunk_mask;

uniform highp sampler2D gunk_noise;
uniform highp sampler2D gunk_normal_map;


float hardstep(float value) {
	float x = clamp(value, 0.0, 1.0);
	return 0.5 * tanh( (20.0 * x - 10.0) * inversesqrt(x - x * x) ) + 0.5;
}

void fragment() {
	vec2 local_uv = UV * uv_scale;
	float value = texture(gunk_noise, local_uv).r;
	vec4 color = mix(color_1, color_2, value);
	float roughness_mix = value * roughness;

	ALBEDO = color.rgb;
	ROUGHNESS = roughness_mix;
	SPECULAR = 0.5 * inversesqrt(specular_contribution);
	NORMAL_MAP = texture(gunk_normal_map, local_uv).xyz;

	float mask = texture(gunk_mask, UV).r;

	// soften edges
	NORMAL_MAP *= smoothstep(1.0, 0.0, mask);

	/*
	// Hard edge
	if(mask + edge_bleed < 0.5) {
		ALPHA = 1.0;
	} else {
		ALPHA = 0.0;
	}
	*/

	// Hardish edge
	ALPHA = hardstep(1.0 - mask + edge_bleed);
}