Light & Obstructions. Your vision is affected by the availability and quality of light and the presence of obstructions.

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Terrain. Difficult terrain slows you down. Some terrain is challenging to traverse, such as a sheet of ice or a tight-rope. Some terrain is dangerous, such as a cliff wall you try to scale or treacherous waters you attempt to swim.​

  

Weather. Snow, rain, or fog can affect your sight. Hot weather can increase your need for water. Certain weather would likely deem your movement as being in difficult terrain.​