#version 450 core
#include "common.glsl"
// Thin, slightly bright streak lit by the overcast sky. Premultiplied alpha.

in vec2 vLocal;
in float vAlpha;
layout(location = 0) out vec4 fragColor;

void main() {
    float across = 1.0 - abs(vLocal.x);
    float along = (1.0 - vLocal.y) * smoothstep(0.0, 0.15, vLocal.y + 0.05);  // bright head, fading tail
    float a = across * across * along * vAlpha * 0.6;
    vec3 c = hemiAmbient(vec3(0.0, 1.0, 0.0)) * 2.0 + uSunColor.rgb * uSunDir.w * 0.2;
    fragColor = vec4(c * a, a);
}