Facade A-A

void mainImage( out vec4 O, in vec2 f ){ vec2 st = (f.xy / iResolution.xy) * 5.0 ;
st.x += step(0.5,mod(st.y, 1.0)) * 0.5; st.x = abs(fract(st.x) - 0.5) + .5; float k = fract(st.x) - fract(st.y); O = vec4(k); }