From Halopedia, the Halo wiki
Pi Studios is a computer game software developer based in Houston, Texas. The company was founded in 2002 by: Robert Erwin, Business Development, John Faulkenbury, Production, Rob Heironimus, Design, Dan Kramer, Programming, Peter Mack, Programming.
They moved from their original location in Plano, Texas to Houston, Texas in January 2005.
Their first commercial work can be found in Activision's Call of Duty: United Offensive. They have also contributed to Call of Duty 2 for the PC and the Xbox 360.