Jevingen:
This will take some experimentation on your part to get the effect you are looking for. At the end of the description of the 3D shape in the 3D script add:
Base
Vert 0, 0, 0
Vert 1, 0, 0
Vert 0, 1, 0
Vert 0, 0, 1
Coor 3, -1, -2, -3, -4
Body –1
Check the GDL Reference Guide for the possible values for COOR, and you can change the values of the first VERT to distort the texture, but I cannot say which ones will work for your situation. You may then also need to add some random numbers for some of these values to get the effect you seek for variations between the columns. Some of these values may depend on whether each column is placed independently, or is referenced as a macro for parts of a larger object (the image looks like balusters to me).
HTH,
David