坐标绘制

• fwidth()

画个坐标系

vec3 NumberPlane(vec2 uv){
  vec3 color = vec3(0.0);
  vec2 cell = fract(uv);

  if(cell.x <= fwidth(uv.x)){
    color += vec3(1.0);
  }
  if(cell.y <= fwidth(uv.y)){
    color += vec3(1.0);
  }

  if(abs(uv.y) < fwidth(uv.y)){
    color = vec3(1., 0., 0.);
  }  
  if(abs(uv.x) < fwidth(uv.x)){
    color = vec3(0., 1., 0.);
  }  
  return color;
}

void mainImage(out vec4 fragColor, in vec2 fragCoord){
  vec2 uv = 3.0 * (2.0 * fragCoord - iResolution.xy) / min(iResolution.x,iResolution.y) ;
  vec3 color = NumberPlane(uv);
  fragColor = vec4(color, 1.0);
}

优化一下

vec3 Grid(in vec2 uv){
  vec3 color = vec3(0.);
  vec2 fraction = fract(uv);
  if(abs(uv.x) <= fwidth(uv.x)){
    color.g = 1.;
  }else if (abs(uv.y) <= fwidth(uv.y)){
    color.r = 1.;
  } else if (fraction.x < 2. * fwidth(uv.x) || fraction.y < 2. * fwidth(uv.y)){
    color = vec3(1.);
  }
  return color;
}

vec2 fixUV(in vec2 c){
  return 3. * ( 2. * c - iResolution.xy) / min (iResolution.x, iResolution.y);
}

void mainImage(out vec4 fragColor, in vec2 fragCoord){
  vec2 uv = fixUV(fragCoord);
  vec3 color = Grid(uv);
  fragColor = vec4(color, 1.0);
}