shader_type canvas_item;

uniform sampler2D trail_texture;

uniform float decay_factor;

void fragment() {
	vec3 orig = texture(trail_texture, UV).rgb;
	float trail = orig.r;

	float sum = 0.0;
	for(float i=-1.0;i<=1.5;i++) {
		for(float j=-1.0;j<=1.5;j++) {
			vec2 offset = vec2(i,j);
			sum += texture(trail_texture, UV + vec2(i,j)).g;
		}
	}
	trail = sum / 9.0;
	trail = trail * decay_factor;
	COLOR = vec4(trail, orig.g, orig.b, 1.0);
}