"Tomb Raider: Underworld" continued the plot line established in "Legend". Crystal Dynamics used new technology to improve the character for seventh-generation consoles, focusing on improving realism. The dirt accumulation and water cleansing mechanic from "Legend" was altered to be a real-time mechanic that can involve the entire game environment. To achieve a more natural appearance, the developers added spherical harmonics to provide indirect lighting to in-game objects like Lara Croft. Crystal Dynamics made the character model more complex and detailed than previous instalments, featuring more texture layers that determine the appearance of shadows and reflective light on it, and using skeletal animation to portray believable movement. The number of polygons in the model increased to 32,000. The developers enhanced Croft's facial model by increasing the number of polygons, bones used in the animation skeleton, and graphical shaders in the face to add more detail and expressive capabilities. The hair was created as a real-time cloth simulation to further add realism to its shape and movement. The developers kept Croft's hair tied back because they felt a real person would not want it flying around while performing dangerous manoeuvres. The character's body size was increased and breast size reduced to portray more realistic proportions.