1. A method for rendering a computer generated image using a stencil buffer, comprising: receiving an arbitrary closed polygonal contour, the contour having N vertices; dividing the arbitrary closed polygonal contour into primitives, each primitive being a polygon having at least 3 and at most P vertices where 2<P<N; setting up a stencil buffer using the primitives; and using the stencil buffer to render the primitives to produce a computer generated image by comparing a winding order of each primitive to an overall winding order of the arbitrary closed polygonal contour and rendering only within areas of an image that are covered by primitives whose winding order is the same as the overall winding order.