\documentclass{minimal} \usepackage{pstricks} \usepackage{pst-solides3d} \pagestyle{empty} \begin{document} \begin{pspicture}(-4,-1)(4,7.5) \psset{viewpoint=50 60 20 rtp2xyz,lightsrc=viewpoint} \psset{solidmemory} \pstVerb{ /mytransform { 3 dict begin /z exch def /y exch def /x exch def z 2 lt { x y z } { x y 4 x dup mul sub z min } ifelse % end } def } \psSolid[object=cylindrecreux, r=2 sqrt, ngrid=6 36, h=4, fillcolor=yellow, transform=mytransform, name=B1, action=none, ] \defFunction[algebraic]{Ftest}(x,y) {4-x^2} {} {} \psSolid[object=surface*, r=2 sqrt, ngrid=4 36, function=Ftest, name=A1, fillcolor=yellow, action=none, ] \psSolid[object=fusion, base=A1 B1, ] \end{pspicture} \end{document}