Hi I am working on a 3D editor for open_gl only, even though directx is nice I feel that updating the old work hourse is a good thing. use z=0 - z scale factor what ever you want and you can make your own 3d Editor
take make everything proportional, Then say z=0- z scale factor, do you see it yet the Z=0 -scale factor brings line size down and creates size for object because off radius of z=0 to some depth like 4.0 you got a radius from screen to the inner depth let click 1 plug in x1,y1,z1 and let click 2 of mouse create the final poly line
glBegin(GL_LINES);
glVertex3f(x1,y1,z1);
glVertex3f(x2,y2,z2);
glEnd();
glSwitchBuffers();
there you go poly lines just for you Enjoy o9i8 Out snoooooZZZZzzzZZZ… 
Z decides yes you got its radius of object.
Draw with z as 1 then draw with z as 4 you will get 2 parallel objects. 4 = z 4 units up the scale
[This message has been edited by o9i8 (edited 02-10-2002).]