Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Traditionally, octrees have been used for ray tracing [Glassner 1984; Fujimoto et al. 1986], background object collision detection [Bandi and Thalmann 1995], motion planning [Hamada and Hori 1996], and other operations which are performed on static objects.
Category: