return (val <= 0.0 || 0.0 <= val) ? false : true;
    }

		void main()
		{
      float a = vUv.x*2.0 - 1.0;
      float b = vUv.y*2.0 - 1.0;
      const float scale = 2.0;

      // Make sure pixels are square
      a *= scale * width / height;
      b *= scale;

      vec2 final_expr = EXPRESSION;

      float L = length(final_expr);
      if(isNan(length(final_expr)) || L > 1.0e10) {
        discard;
      }

      // TODO : Make this user-controlled
      if(false) {
        // HSV Domain Coloring

     