This is due to the Set Datum command's current setting. Select the Action menu, select Set Datum command. The Set Datum dialog allows you to specify the orientation of the vessel (horizontal or vertical) and where the "datum" line should be, either at the top or bottom of the vessel. If datum is set at the top of the vessel the Z axis will point down. Change the selection to datum at bottom of the vessel and Z will point up.

I personally prefer datum at the bottom. In this case the datum will regularly "drop" to the bottm as the vessel model is constructed component by component. This can be disconcerting to some people. I sometimes get vessel files at Codeware where users have elected to have datum at the top. I suppose the users like to have a "fixed" datum that doesn't move on them.

The 3D graphics used by COMPRESS has a "light source" to create shadows and highlights. There are differences in light and shadows between datum at the top or bottom and the graphic may look different. There is no real benefit to selecting one datum over the other.



  Tom Barsh
  Codeware Technical Support

Hi Tom,

Though the Datum line will not bother the vessel dimensions and other factors, I too prefer to have the datum at the bottom, so that the Z-axis points upwards.

Thanks,
Aravind Sujay