Whiteout can be caused a number of ways. Typically whiteout is caused by an even dense layer of low cloud over a snow field. The sun light is heavily diffused through the cloud, and then further scattered while reflecting between the snow surface and cloud layer. The lack of a single light source results in a lack of definition. Someone faced with whiteout conditions will not have many of the cues used for judging depth and large objects in the distance may look like near small objects, and vice versa. The complete lack of shadows will result in light and white coloured objects blending in to the snow surface making walking on uneven surfaces, such as caused by snow ridges or sastrugi, very difficult, and approaching drops such as ice cliffs extremely dangerous. Without a horizon judging up becomes difficult and can result in a lack of orientation and balance.
Typical whiteout caused by a low cloud cover can still have good surface visibility with dark coloured objects appearing to float. But whiteout can occur due to blizzard conditions with very low surface visibility due to blowing snow, or heavy fog, also resulting in poor surface visibility. In these low visibility conditions everything is white and no objects can be seen and complete disorientation can occur. Travel in these conditions can be very dangerous due to unseen objects and terrain.
Whiteout conditions caused by blowing snow in a blizzard. Travel is difficult and dangerous not only because of hidden dangers and disorientation, not only optically but because of the battering wind.