Added balatroesque gunk material

assets/materials/gunk_2_material.tres

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+[gd_resource type="ShaderMaterial" load_steps=3 format=3 uid="uid://kfyacbbge0xi"]
+
+[ext_resource type="Shader" path="res://src/shaders/gunk_2.gdshader" id="1_nrrfp"]
+[ext_resource type="Texture2D" uid="uid://8cm835h4gxwe" path="res://assets/debug_mask.png" id="2_kh76g"]
+
+[resource]
+render_priority = 0
+shader = ExtResource("1_nrrfp")
+shader_parameter/color_1 = Color(0, 0.101961, 0.301961, 1)
+shader_parameter/color_2 = Color(0.1289, 0.123, 0.3, 1)
+shader_parameter/color_3 = Color(0, 0.039, 0.13, 1)
+shader_parameter/spin_rotation = 0.0
+shader_parameter/offset = Vector2(-0.35, 0.235)
+shader_parameter/contrast = 2.0
+shader_parameter/spin_amount = 7.98
+shader_parameter/pixel_filter = 700.0
+shader_parameter/convolution_factor = 0.05
+shader_parameter/roughness = 0.15
+shader_parameter/specular_contribution = 0.2
+shader_parameter/uv_scale = Vector2(1, 1)
+shader_parameter/time_scale = 0.01
+shader_parameter/edge_bleed = 0.1
+shader_parameter/gunk_mask = ExtResource("2_kh76g")

src/shaders/gunk_2.gdshader

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+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 vec4 color_3: source_color = vec4(0.1, 0.35, 0.4, 1.0);
+
+uniform highp float spin_rotation;
+uniform highp vec2 offset = vec2(0.0, 0.0);
+uniform highp float contrast = 2.0;
+uniform highp float spin_amount = 0.36;
+uniform highp float pixel_filter = 700.0;
+#define SPIN_EASE 1.0
+
+uniform float convolution_factor = 0.05;
+
+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 time_scale = 1.0;
+
+uniform float edge_bleed = 0.1;
+
+uniform sampler2D gunk_mask;
+
+
+float brightness(vec3 color) {
+	return 0.2 * color.r + 0.7 * color.g + 0.1 * color.b;
+}
+
+// Balatro-esque effect
+vec4 effect(highp vec2 scaled_uv) {
+	// Pixellate
+	highp vec2 uv = floor(scaled_uv.xy * pixel_filter) / pixel_filter - 0.5 - offset;
+	highp float uv_len = length(uv);
+	
+	// Adding in a center swirl, changes with time. Only applies meaningfully if `spin_amount` != 0
+	highp float speed = 0.2 * SPIN_EASE * spin_rotation + 302.2;
+	highp float new_px_angle = atan(uv.y, uv.x) + speed - 20.0 * SPIN_EASE * uv_len;
+	uv = uv_len * vec2(cos(new_px_angle), sin(new_px_angle));
+	
+	// Now add the paint effect to the swirled uvec2
+	uv *= 30.0;
+	speed = TIME * time_scale;
+	highp vec2 uv2 = vec2(uv.x + uv.y);
+	
+	for(int i = 0; i < 5; i++) {
+		uv2 += sin(max(uv.x, uv.y)) + uv;
+		uv += 0.5 * vec2(cos(5.1123314 + 0.353 * uv2.y + 0.131121 * speed), sin(uv2.x - 0.113 * speed));
+		uv -= cos(uv.x + uv.y) - 1.0 * sin(0.711 * uv.x - uv.y);
+	}
+	
+	// Adjust contrast & clamp on [0, 2]
+	highp float contrast_mod = 0.25 * contrast + 0.5 * spin_amount + 1.2;
+	highp float paint_res = clamp(0.035 * contrast_mod * length(uv), 0.0, 2.0);
+	highp float c1p = max(0.0, 1.0 - contrast_mod * abs(1.0 - paint_res));
+	highp float c2p = max(0.0, 1.0 - contrast_mod * abs(paint_res));
+	highp float c3p = 1.0 - min(1.0, c1p + c2p);
+	
+	return 0.3 * color_1 / contrast + (color_1 * c1p + color_2 * c2p + vec4(c3p * color_3.rgb, c3p * color_1.a)) * (1.0 - 0.3 / contrast);
+}
+
+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;
+	vec4 effect_color = effect(local_uv);
+	float value = brightness(effect_color.rgb);
+	float roughness_mix = value * roughness;
+
+	ALBEDO = effect_color.rgb;
+	ROUGHNESS = roughness_mix;
+	SPECULAR = 0.5 * inversesqrt(specular_contribution);
+	
+	// Convolutional normal map
+	float sample_step = convolution_factor / pixel_filter;
+	float n = sqrt(brightness(effect(vec2(local_uv.x, local_uv.y - sample_step)).rgb));
+	float s = sqrt(brightness(effect(vec2(local_uv.x, local_uv.y + sample_step)).rgb));
+	float e = sqrt(brightness(effect(vec2(local_uv.x + sample_step, local_uv.y)).rgb));
+	float w = sqrt(brightness(effect(vec2(local_uv.x - sample_step, local_uv.y)).rgb));
+	float x = 0.5 * (w - e) + 0.5;
+	float y = 0.5 * (s - n) + 0.5;
+	NORMAL_MAP = vec3(x, y, clamp(1.0 - abs(x - 0.5) + abs(y - 0.5), 0.5, 1));
+	
+
+	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);
+}