Shader analytical approximations for terrain animation in "The Time Machine"

For The Time Machine the CG effects team faced the daunting task of producing imagery that represented long exposure and time-lapse photography of various types of terrain. The scope of the effort and the shot design largely preempted the use of simulated or exclusively explicit techniques for terrain construction. The challenge we faced was to procedurally model surface detail features into terrain that would visually represent the erosion of volumes of earth and rock over time. These features had to be consistent over time and through the entire volume of earth and rock through which the terrain would erode. These restrictions gave rise to two shader techniques used both in the procedural construction of geometry and in the displacement phase of terrain shading: bouldering and gulleying.