Hello Just been play with a feature I have not used before. First It would be clearer if on p20 of the thbook the paragraph under vthreshold If passages are _more_or_less_ vertical (inclination > vthreshold), even UD becomes perpendicular to the shot – otherwise passages would not look very good. The 'more or less' is very confusing It would read better if it read If passages are _about_ vertical (inclination > vthreshold), even UD becomes perpendicular to the shot – otherwise passages would not look very good. Also In some passages NSEW is not not always the best way to measure passages, rifts on the like. So for some I have dimensions measured as NW SE NE SW, possible allowing an ofset for vthreshold would be a way of solving this. eg vthreshold-offset 45 degree Just a thought for the future. thanks Andrew