The representation of figures in a naturalistic fashion is a central concern of Renaissance art.  From the end of the thirteenth century Italian artists were attempting to suggest solid forms existing in a three-dimensional world through the use of modeling and foreshortening, although these early works tended to exhibit some inconsistencies in the treatment of anatomy.  By the end of the fifteenth century artists were beginning to study anatomy in a more scientific fashion that allowed for considerable accuracy in the treatment of the human form.  

Renaissance Figures 

Left:  Figures  are modeled, but their bodies are elongated.
Right:  Figures are modeled and cast shadows, and difficult foreshortening is added. Heads are still somewhat small.

Pietro Cavallini, Last Judgment, S. Cecilia, Rome, c. 1291

Masaccio, Tribute Money,  Florence, c. 1426

Left: The figure is modeled and in a difficult pose, and the artist has clearly studied anatomy, for the physical details are represented with almost scientific accuracy. 

Antonio Pollaiuolo, Hercules, Uffizi, Florence, c. 1460

Raphael, School of Athens, Rome, c. 1510