lmg grid overlay

new_gist_file

uniform vec2 gridSize;
const vec4 gridColor = vec4(1.0,0.5,0.0, 0.1);
const float gridLineWidth = 0.03;
const float gridLineFade = 0.01;

    // overlay grid
    vec2 xy = vUv * gridSize;
    vec2 dGrid = abs(xy - floor(xy+0.5)); // floor(i+0.5) == round
    vec2 d = min( 2.0 * abs(dGrid) - (gridLineWidth/2.0 - gridLineFade), gridLineFade) / gridLineFade;
    gl_FragColor.rgb = mix( gl_FragColor.rgb, gridColor.rgb, (1.0 - min(d.x,d.y)) * gridColor.a );