struct _Utils {
float Random(float2 st) {
    return frac(sin(dot(st, float2(12.9898,78.233)))*43758.5453123);
}} Utils;
float2 st = UV * GridSize;
st.y = st.y - Time * Speed;
float2 ipos = floor(st);
float2 fpos = frac(st);
if (fpos.y > (1.0 - PaddingY)) {
    discard;
}
float color = Utils.Random(ipos);
if(color < LowerBound || color > UpperBound) {
    discard;
} else {
    color = 1.0;
}
return float3(color, color, color);