#version 150
uniform float width;
in vec2 f_normal;
out vec4 out_color;
void main() {
float feather = width/2.0;
float l = length(f_normal) * width;
float d = 1 - l;
float a;
if (l > width - feather) {
d = l - (width - feather);
a = 1 - d / feather;
} else {
a = 1;
}
out_color = vec4(0, 0, 0, a);
}