To make virtual sculptures one needs a software for digital 3D modeling.
Digital 3D modeling has important applications in many disciplines, including engineering, design, advertisement and the movie industry. As a result, there are nowadays many software products which can be used for virtual sculpture. Notable examples are 3D Studio Max, Maya and Zbrush; a comprehensive list can be found in Wikipedia.
Some of the software products focus on creation of 3D bodies, and other on creating scenes or animations. A common feature to most of these programs is the use of functions which mimic the actions in the material world. Since anybody can imagine and easily understand such actions, this approach facilitates the learning of the corresponding programs.
My favorite software programs belong to another class; they use mathematical formulas and algorithms to create the 3D bodies. The aesthetical appeal of mathematically created shapes and bodies was noted and admired since the ancient period, with perhaps the great pyramids being the most notable example. Such programs have hardly any use other than art, and cannot attract commercial funding. As a result most programs of this category are written by devoted volunteers and are distributed free of charge.
Picture credit: By De Hass, Frank S [Public domain or Public domain], via Wikimedia Commons