Fractals are used in many computer games to render realistic graphics for mountains, landscapes & 3D terrains, especially for flight simulations, computer games, digital artworks & animations. Rather than storing a huge amount of detailed height data in the computers memory, fractal-based algorithms generate the data 'on-the-fly' to render realistic landscapes in real-time. Algorithms for generating fractal-based landscapes take advantage of the 'self-similarity' which exist in the natural world to render visually rich and complex images with attention to fine detail at all scales to appear smooth and not suffer from 'pixelation' even when zooming in close.
These algorithms use methods such as recursive subdivision and fractional Brownian motion to generate a 3D landscape which is then smoothed using a variety of techniques such as image filtering and polynomial interpolation (splines & Bezier curves) to generate photorealistic images of rolling hills & other natural scenes.
Pioneers in this field include Ken Musgrave, digital artist and CEO of Pandromeda (http://www.pandromeda.com/) and Loren Carpenter who went on to form Pixar Studios.