rose-curve/rose_curve.tscn at master · Lander-Godot/rose-curve · GitHub

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[gd_scene load_steps=4 format=2]

[ext_resource path="res://rose_curve.gd" type="Script" id=1]

[sub_resource type="Shader" id=1]
code = "shader_type canvas_item;

// TODO: Proper denominator handling
// TODO: Automatic iteration count calculation

uniform float scale: hint_range(0.0, 10.0) = 1.0;
uniform float offset = 0.0;

uniform float numerator: hint_range(1, 7);
uniform float denominator: hint_range(1, 9);

uniform int max_iters: hint_range(1, 4096) = 8;

uniform bool use_time = false;
uniform float time = 0.0;

const float PI = 3.14159;
const float TAU = 6.28318;
const float INF = 1.0 / 0.0;

vec2 center_uv(vec2 uv) {
	return (uv * 2.0) - 1.0;
}

vec2 cartesian_to_polar(vec2 cartesian) {
	// Radius
	float r = length(cartesian);

	// Angle
	float theta = atan(cartesian.y, cartesian.x);

	if(cartesian.y < 0.0) {
		theta += TAU;
	}

	return vec2(theta, r);
}

// Normalized sine - takes input in 0..1 range instead of 0..PI
float sin_norm(float k) {
	return sin(k * PI);
}

// Normalized cosine - takes input in 0..1 range instead of 0..PI
float cos_norm(float k) {
	return cos(k * PI);
}

void fragment() {
	vec2 uv = center_uv(UV);

	vec2 polar = cartesian_to_polar(uv);
	float o = polar.x;
	float r = polar.y;

	float k = numerator / denominator;

	float dist = INF;

	float cycle_fac = 0.5 * cos_norm(k) + 0.5;
	float denom = 1.0 / k;
	float denom_fac = 0.5 * cos_norm(denom) + 0.5;

	float curve_length;
	float curve_step = curve_length / k;
	if (k >= 1.0) {
		 curve_length = PI * cycle_fac;
		curve_step = curve_length / k;
	}
	else {
		 curve_length = PI / (denom + denom_fac);
		curve_step = PI;
	}

	int iters;
	if (k >= 1.0) {
		iters = max_iters;
	}
	else {
		iters = max_iters;
	}

	for(int i = 0; i < iters; ++i) {
		float lo = o - (float(i) * curve_step);
		float ko = k * lo;
		float c = cos(ko);
		float lr = scale * c + offset;
		float d = abs(r - lr);
		dist = min(dist, d);
	}

	vec2 frag_size = fwidth(UV);
	float frag_width = max(frag_size.x, frag_size.y);
	frag_width /= polar.y;
	frag_width *= scale;
	frag_width *= max(1.0, k);
	frag_width *= 2.0;

	float fac = smoothstep(frag_width, 0.0, dist);

	COLOR = vec4(vec3(fac), 1);
}"

[sub_resource type="ShaderMaterial" id=2]
shader = SubResource( 1 )
shader_param/scale = 1.0
shader_param/offset = 0.0
shader_param/numerator = 5.0
shader_param/denominator = 7.0
shader_param/max_iters = 10
shader_param/use_time = false
shader_param/time = 0.0

[node name="Control" type="ColorRect"]
anchor_right = 1.0
anchor_bottom = 1.0
color = Color( 0, 0, 0, 1 )
script = ExtResource( 1 )

[node name="ColorRect" type="ColorRect" parent="."]
material = SubResource( 2 )
anchor_left = 0.5
anchor_top = 0.5
anchor_right = 0.5
anchor_bottom = 0.5
margin_left = -254.311
margin_top = -255.5
margin_right = 256.689
margin_bottom = 255.5