Flux variations of 3C 454.3 at γ-ray (top) and optical (middle) frequencies in late 2009. The γ-ray light curve is built with Fermi data (crosses) from Ackermann et al. (2010) and AGILE data (triangles) from Pacciani et al. (2010). Vertical dotted lines indicate remarkable optical events. Cubic spline interpolations through the 7-day binned optical (blue dashed line) and γ (black dashed line) light curves are also shown. They represent the variations due to geometrical changes. The evolution of the Doppler factor δ (dot-dashed lines) and viewing angle θ (solid lines) is shown in the bottom panel for both the γ-ray (black) and optical (blue) bands.