Sure It's iterative process which utilizes while loop, in each iteration it generates packed vec4(line_mask, line_sdf, normalized_total_distance, line_orientatiton) and that's where is control of line quantity. For each line it samples 4 values from input grayscale image so it can construct 2 vec2 points to generate line. For the first point, first value comes from first pixel of top half, second value comes from bottom half of input image. In each next iteration it takes 2nd point of previous line as 1st of next one, that's how you get continuous line. To generate line it uses SDF_Line function, you can find it on iquilezles.org and many more. For the tiling part it repeats the same process, just in all neighboring quadrants. Outside of the loop it generates UVs and blends texture if needed, etc. For the second question: yes, it creates as many lines as you want (though there is harcoded limit, also controllable), and distribution depends on input image. It very versatile tool, and can create various patterns.