Hi Maurice, As Elaine pointed out there is no way to flexibly smooth a surface edge in Chimera right now. I wrote a little Python code that creates a new mouse mode in Chimera that allows you to hide individual triangles of a surface by clicking on them. It is attached to this email. You open it in Chimera (File / Open) then hold the ctrl key and click with the right mouse button (of a 3 button mouse) and it will hide the triangle. I tested this with the June 4 Chimera daily build. It definitely will not work in the Chimera 1.2470 production release (Nov 2007). http://www.cgl.ucsf.edu/chimera/alpha-downloads.html This has lots of limitations to beware of. Saving a Chimera session will not remember the hidden triangles. So basically all you can do is trim triangles, save an image, then lose your trimming when you quit Chimera. Also there is no way to reshow specific hidden triangles. Using Actions / Surface / show or hide will undo the effect of all your hiding though. Enjoy, Tom # # Mouse mode (ctrl-right-mouse-button) to delete individual surface triangles. # Open this file in Chimera to activate the mouse mode. # # Warning: Deleted triangles will not be recorded in Chimera session files. # # Tested in Chimera version 1.2524, daily build from June 4, 2008. # Will not work in production release 1.2470 from Nov 2007. # def mouse_down_cb(viewer, event): from VolumeViewer import slice xyz_in, xyz_out = slice.clip_plane_points(event.x, event.y) import PickBlobs smlist = PickBlobs.surface_models() dist, p, tri = PickBlobs.closest_surface_intercept(smlist, xyz_in, xyz_out) if p is None: from chimera.replyobj import status status('Missed surface (%d,%d)' % (event.x, event.y)) return m = p.triangleAndEdgeMask if m is None: # No triangles hidden yet from numpy import zeros, int32 m = zeros((p.triangleCount), int32) m.fill(0xf) # Convert masked geometry triangle index to full geometry index t = (m&0x8).nonzero()[0][tri] m[t] ^= 0x8 # Toggle triangle display. p.triangleAndEdgeMask = m import Surface if hasattr(Surface, 'set_visibility_method'): Surface.set_visibility_method('static', p.model) from chimera import mousemodes as m m.addFunction('hide triangle', (mouse_down_cb, None, None)) m.setButtonFunction('3', ['Ctrl'], 'hide triangle')