zdrawPoint

send current position in scene to render object, and render in accordance with style sttribute

If on update, traced point has moved within limits defined by 'mintrace' and 'maxtrace' append its new position to the trace curve

Re-intialize list of loci points to None

Re-intialize list of traced curves to None

For consistency in iterating Element's rendering objects, all elements rendering information is in a list called self.rend. In the case of Points, it is either a single element list, containing a cvisual sphere object, or a 2 element list with each element an oriented cvisual pyramid object, which together form a diamond shape representing the point

export the scene's points to PovRay SDL