Martin Kraus: Direct Manipulation of Parametrized Graphics
  Parametrized Graphics

  First example:
  
<HTML>
<APPLET 
  ARCHIVE="live.jar" 
  CODE="Live.class" 
  WIDTH=400 HEIGHT=400>
<PARAM 
  NAME="INDEPENDENT_VARIABLES"
  VALUE="{x->3,y->-2,z->1}">
<PARAM 
  NAME="INPUT"
  VALUE="Graphics3D[{
    Line[{{0,0,0},{x,y,z}}],
    PointSize[0.08],
    Point[{x,y,z}],
    PointSize[0.04],
    Point[{x/2,y/2,z/2}]}]">
</APPLET>
</HTML>