<div>                Dear Herbert, thanks for reply.<br><br>Probably I'm doing something wrong.<br><br>First, to generate the object, file pst3d.tex<br><br>\documentclass{article}<br>\usepackage{pstricks,pst-solides3d}<br>\begin{document}<br>\begin{pspicture}(-7,-2)(7,4)<br>\psset{lightsrc=80 30 30}<br>\psset{viewpoint=1000 60 20 rtp2xyz,Decran=1000}<br>\psframe(-7,-2)(7,4)<br>\psset{solidmemory}<br>\codejps{/a 2 def /b 2 def}%<br>\defFunction[algebraic]{F3}(t)<br>    {a*(1+cos(t))}<br>    {b*tan(t/2)}<br>    {a*sin(t)}<br>\defFunction[algebraic]{F3'}(t)<br>    {-a*sin(t)}<br>    {b*(1+tan(1/2*t)^2)}<br>    {a*cos(t)}<br>\psSolid[object=courbe,<br>    range=-2.7468 2.7468,<br>    ngrid=72 12,<br>    function=F3,hue=0 1 0.7 1,<br>    action=none,name=H1,<br>    r=1]%<br>\psSolid[object=cylindrecreux,<br>    h=20,r=1,RotX=90,<br>    incolor=green!30,action=none,<br>    name=C1,<br>    ngrid=36 36](2,10,0)<br>\psSolid[object=fusion,<br>    base=H1 C1,<br>    filename=horoptere,<br>    action=writesolid]<br>\composeSolid<br>\end{pspicture}<br>\end{document}<br><br>and run latex + dvips + gs as:<br><br>$ latex pst3d.tex<br>$ dvips pst3d.dvi<br>$ gs -dNOSAFER pst3d.ps<br><br>this generate all 4 files horoptere-*.dat.<br><br>Now, to load the horoptere, file pst3d_load.tex<br><br>\documentclass{article}<br>\usepackage{pstricks,pst-solides3d}<br>\begin{document}<br>\begin{pspicture}(-5,-3.5)(4,3)<br>\psset{lightsrc=80 30 30}<br>\psset{viewpoint=100 60 20 rtp2xyz,Decran=75}<br>\psframe*[linecolor=cyan!30](-4.5,-3)(3.5,3)<br>\psSolid[object=datfile,filename=horoptere]<br>\end{pspicture}<br>\end{document}<br><br>and run latex + dvipdf as<br><br>$ latex pst3d_load.tex<br>$ dvipdf -dNOSAFER pst3d_load.dvi<br><br>file pst3d_load.pdf has both cylinders with white colours faces.<br><br>Any idea of why the twisted cylinder is not with colours faces?<br><br>Thanks,<br>Leonardo            </div>