Hello Martin,<BR> <BR>how many thousands of actors do you have? I am asking because rendering performance is not only limited by the number of vertices and triangles you have but by the number of objects too. This has more to do with OpenGL than with VTK. I think this is explained in more detail in:<BR>"<SPAN style="mso-ansi-language: EN-GB" lang=EN-GB><FONT size=2>Cebenoyan, C. (2004<I style="mso-bidi-font-style: normal">): Graphics Pipeline Performance</I>. In: GPU Gems, Edited by Randima Fernando, Addison Wesley, <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place w:st="on"><st1:City w:st="on">Boston"</st1:City></st1:place></FONT><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN><BR>I believe that NVidia has made this available online.<BR> <BR>If this is your problem, than you need some datastructure that allows to efficiently cull away the objects that are not visible (e.g. a quadtree). Are all objects (vtkActors) visible at the same time? If yes, you might need to make some assumptions, such as that the users can only pick objects that are near, and combine these culling techniques with Level Of Detail techniques. I am not sure if such an implementation can be done with VTK, may be you need a scenegraph that is targeted at rendering, such as OpenSG or OpenSceneGraph.<BR> <BR>Kind regards,<BR>Björn Zehner<BR><SPAN style="mso-ansi-language: EN-GB" lang=EN-GB><FONT size=2><st1:place w:st="on"><st1:City w:st="on"> </st1:City></st1:place></FONT></SPAN><BR><BR>------------------------------------------------------------------------- <BR>Dr. Bjoern Zehner <BR>UFZ Centre for Environmental Research Leipzig-Halle <BR>Permoserstrasse 15 <BR>04318 Leipzig <BR>Germany <BR>http://www.ufz.de/index.php?en=5673 <BR>Tel: ++49 (341) 235 1979 <BR>Fax: ++49 (341) 235 1939<BR><BR>