Edge Tracing Shader in Godot

EdgeTracingShader

shader_type canvas_item;

uniform sampler2D tex;
uniform float intensity;
uniform vec4 color : hint_color;
uniform float speed;

float sample(in vec2 st){
	return texture(tex, st).a;
}

void fragment(){
	float t = TIME*speed;
	vec2 px = vec2(1.)/vec2(textureSize(tex, 0));
	
	float neighbor = 
		sample(UV+px*vec2( 1.,  0.))+
		sample(UV+px*vec2( 0.,  1.))+
		sample(UV+px*vec2(-1.,  0.))+
		sample(UV+px*vec2( 0., -1.));
	
	float center = sample(UV)*4.;
	
	float edge = clamp(neighbor-center, 0., 1.);
	float lit = dot(UV-vec2(.5), vec2(cos(t), sin(t)))-t;
	lit = mod(lit, 1.);
	lit = pow(lit, 12.);
	
	COLOR = vec4(color.rgb*vec3(intensity), edge*lit);
}