\documentclass{article} \usepackage{pst-solides3d} \begin{document} \pagestyle{empty} \begin{pspicture*}(-3,-3)(4.5,5) \psset{lightsrc=viewpoint,viewpoint=5 -5 3,Decran=10} \defFunction{G}(t) {t} {t dup mul .25 mul} {-2} \psframe(-3,-3)(4.5,5) \psSolid[object=cone, r=1, h=1](-2,10,0) \psSolid[object=cone, function=G, range=-3 2, ngrid=3 10, origine=0 0 0, ] \end{pspicture*} \end{document}