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That was really advanced code 

Some questions I have about the code, maybe you can help me to understand it better:

object0 - Create event
{
    maxdistortion = 0.4;    // maximum amount of distortion to apply
    octaves = 4;            // number of fractal noise octaves
    scale = 2/256;          // scale of fractal noise Why this number? I meant the 2, because 256 is the size of the texture right? If I make a smaller texture, should i change all 256 by 128 for example?
   
    noise_init();
   
    surfWind1 = -1;
    surfWind2 = -1;
    row = 0;
}

object0 - Draw event
{
    if (surface_exists(surfWind1) && surface_exists(surfWind2))
    {
        var i,j,k;
        if (row < 256)
        {
            // select surfWind1 for the texture
            var tex = surface_get_texture(surfWind1);
           
            draw_set_color(c_white);
            surface_set_target(surfWind2);
            draw_primitive_begin_texture(pr_pointlist,tex);
           
            // find the vertical texture coordinate for the pixel
            var v = row/256;
           
            // modulate the distortion to be minimal at the top and bottom edges
            var distortion = maxdistortion * (1 - abs(2*v-1));
           
            // draw a row
            for (i=0; i<256; i+=1)
            {                   
                // find the horizontal texture coodinate for the pixel
                var u = i / 256;
               
                // map the pixel to a point in solid texture spaceOk, the values here are related to the previous scale variable and the pixel position on the "grid"
                var px = scale * i;
                var py = scale * row;
                var pz = 0;
               
                // perturb the horizontal texture coordinate with fractal noise Here is where i imagine the horizontal distortion is produced right?
                var uu = u + distortion * fbm(px,py,pz,0.85,2.0,octaves);
               
                // map the pixel to a different point in solid texture space Why this values?
                px += 1.2;
                py += 1.5;
                pz += 1.8;
               
                // preturb the vertical texture coordinate with fractal noiseAnd here the vertical distortion
                var vv = v + distortion * fbm(px,py,pz,0.85,2.0,octaves);
               
                // draw the pixel with the perturbed texture coordinate
                draw_vertex_texture(i,row,uu,vv);
            }
            draw_primitive_end();
            surface_reset_target();
           
            // advance to next row
            row += 1;
        }
        draw_surface(surfWind1,0,0);
        draw_surface(surfWind2,256,0);
    }
    else
    {
        draw_set_color(c_red);
        draw_set_font(font0);
        draw_text(10,10,"SURFACE ERROR");
    }
}


Thank you very much!