I read a story in which King Udayana of Vatsa sent an artist in heaven to carve a figure of the Buddha. I will tell this story later in future but, this statue that was carved is said to be the original sculpture. This sculpture exists in India and later replicas were made by Chinese and Japanese artists. It is also said all other images of Buddha was a replica of this original statue.
Buddha image was based on various cultural and artistic factor that can be traced back in early Gandhara and Mathura art. Artists were faced with the problem of conveying Buddha’s excel nature into human figure. This was not an easy task.
The image of the Buddha in a standing posture was to a large extent modelled upon an ancient Mathura type of figure. The smooth close fitting robe almost devoid of any draping folds, which left large expanses of the body uncovered.
The Gandhara art mainly has Buddha concentrating his gaze upon a single point, imbued with the peace of nirvana, like a lamp burning but not flickering at all.
Mathura and Gandhara art developed iconographic features symbolizing Buddha’s superhuman nature as the Enlightened one which remained standard throughout Asia.
Citation: The Art of Buddhism by Dietrich Seckel