godot spiral shader

spiral.shader

shader_type canvas_item;

const float PI = 3.14159265358979323846;
const float w = 0.1; // Width of line

void fragment() {
	float dis = 0.1; // Displacement (spacing) of lines
  
	// Get an angle value around a circle of 0.0 .. 1.0
	vec2 pt = (UV - vec2(0.5)) * 2.0; // +/-1.0
	float ang = (atan(pt.y / pt.x) / PI * 2.0 + 1.0) / 4.0; // 0.0 .. 0.5
	if (pt.x < 0.0) ang += 0.5;
  
	// Get a color value based on a point on the spiral
	float radius = ang * dis + length(pt);
	float circles = fract(radius / dis); // 0 .. 1
  
	// Anti-alias the curve
	if (radius < 1.0)
		COLOR = (smoothstep(circles - w, circles, w) - smoothstep(circles, circles + w, w)) * vec4(0.0, 0.8, 0.4, 1.0);
	else
		COLOR.a = 0.0;
}