We experimentally study the bidimensional structure of the internal gravity waves generated in a stratified environment by oscillating prisms of similar size and rhomboid and square cross-section shape. By measuring the density gradient using synthetic Schlieren, the density variations field is built, while applying the particle image velocimetry technique the horizontal and vertical components of velocity are measured and vorticity distribution is determined. The distinctive physical features of the fields produced are determined for three different frequencies of oscillation and compared with those of the well-known case of an oscillating cylinder. The optimized digital processing of the images allows knowing new aspects about the formation (transient phase) and evolution (steady state phase) of the internal waves for bodies of different cross-section shape.