"Further complicating level streaming, the design for Soul Reaver also called for dimensional shifting. During gameplay, players swap between the spectral and material planes - a key gameplay concept that ties in closely to both puzzle-solving and storytelling. Loading two different versions of the map would have placed too much strain on an already heavy system, but Crystal Dynamics' solution was elegant, innovative and efficient. The same basic map data is utilised, but geometry is mapped to different coordinates in each version of the level. Shifting between planes interpolates from one set of geometry to the other. Per-vertex colour data is also modified when shifting between planes, adding further to the illusion."