Hi Pradeep, Here's a Python script to draw a circle. The inner/outer radius, subdivisions, color are set at the bottom of the script and you can edit those. You just open the script with File / Open to create the circle. Use the "active" buttons in Model Panel to move the circle to the desired position and orientation. This script works with Chimera 1.2502 and other recent daily builds. It will not work with the Nov 2007 production release. Tom # ----------------------------------------------------------------------------- # Create an annulus. # def annulus(rinner, router, n, color): from numpy import zeros, single as floatc, intc, arange vertices = zeros((2*n,3), floatc) from math import pi, sin, cos for i in range(n): ai = i*2*pi/n ao = (i+0.5)*2*pi/n vertices[i,:] = (rinner*cos(ai), rinner*sin(ai), 0) vertices[n+i,:] = (router*cos(ao), router*sin(ao), 0) triangles = zeros((2*n,3), intc) triangles[:n,0] = arange(n) triangles[:n,1] = (triangles[:n,0]+1)%n triangles[:n,2] = n + triangles[:n,0] triangles[n:,0] = triangles[:n,0] triangles[n:,1] = triangles[:n,2] triangles[n:,2] = n + (triangles[:n,0]-1)%n from _surface import SurfaceModel s = SurfaceModel() s.addPiece(vertices, triangles, color) s.piecesAreSelectable = True from chimera import openModels openModels.add([s]) # ----------------------------------------------------------------------------- # annulus(rinner = 10, # inner radius router = 12, # outer radius n = 100, # circle subdivisions color = (1,1,1,1), # red, green, blue, opacity )