Realistic rendering of human models has an increasing importance in computer graphics. Simulation of muscle bulging and proper deformations of skin at joints, makes human animation more realistic. In this thesis, we describe a layered human animation system in which muscles move with respect to the bones and the skin deforms according to the muscles. Muscles are modelled as ellipsoids and their shapes are deformed with the movements of the bones represented by sticks in the skeleton. The skin is anchored to the muscles and it changes its shape as the muscles bulge. Every muscle may have different user defined bulging ratios according to the joint movements.