Approached them during school career fair. One informational interview one on one, later two screenings, one for math and other for programming. Later one full day on site interview starting with presentation on past experience and research followed by four one on one sessions about Algorithms, math, mesh generation, rendering etc. I had also applied for internship

Technical phone interview with shared editor after an initial phone screening. Each interview took an hour. The technical interview was all in C++ using a shared editor.