Hello,I'm fairly new to the dynamic blocks after being away from AutoCAD for a few years. Working for a railroad-design company we create most drawings as 2D plans, but use a lot of 3D lines (poly or spline) especially for the centerline of the tracks. I have created some dynamic blocks that need to be placed aligned to the centerline of the track. It works OK if the centerline is 2D, but when I try to align it to a 3D line, the block is not rotating.Is this a limitation of AutoCAD and/or the dynamic block definition, or am I missing something ?With regards,  Gerbert Verheij, NL

All your dynamic blocks behave this way or just specific ones?
What makes a polyline 3D?

All my blocks that use the alignnent grip behave in the same way: no problems on a 2D line, and no rotation when placing the block on a 3D line.By 3D line I mean a 3DPOLY or SPLINE where not all the nodes have the same elevation, i.e. the line moves along the X, Y and Z-axis.Gerbert

And the reason for doing a 2D drawing using 3dpolylines and splines is...?  I can't seem to wrap my mind around the concept.  Can you post a sample block you are using?  I'd like to attempt what you are trying to do.

The data we use is delivered to us from survey teams or existing datasets.
We design the tracks in 3D (for elevated crossings and bridges like in the drawing), but for
plotting we make 2 drawings:- a plan view with all surroundings- a
profile 'or side' view for the elevationsSo a single data-set with different
outputs. The blocks will be used by the people designing the overhead lines, and they use the elevations in the calculation of wire tension and stuff like that. 
You can find the drawing here (I hope the link works), it contains 6 centerlines for the
railroadtracks that cross at different elevations and one of the blocks i'm trying to
place. As you can see it works on the spline and not on the polylines.Thanks for your interest ! Gerbert
AGVerheij2011-03-09 09:36:28

Tried your link but I.E. 8 had a problem with it.
Thanks for the explanation though.  Makes more sense now.