Creo Simulate > Reference Links > Using the Coordinate System Option
  
Using the Coordinate System Option
When you select Coordinate System, Creo Simulate determines the material orientation by projecting the World or UCS directions onto the surface or shell, or into a solid. Material Direction 3 remains perpendicular to the surface or shell.
Depending on the entity you select:
For surfaces and shells, Creo Simulate displays the current coordinate system (the WCS is selected by default). You can select another coordinate system if you wish.
For parts, solids, volumes, 2D plates, and 2D solids, Creo Simulate displays Material Directions 1, 2, and 3, which you can change on the dialog box if you like.
A menu appears that lets you define the following items:
Projected x axis—This option is the default value, and the only available choice in FEM mode. It defines Material Direction 1 to be the direction of the x-axis of the coordinate system projected onto the surface.
Projected closest axis—This option defines Material Direction 1 through a series of calculations.
To calculate this value, the software first determines which of the three coordinate system directions—(X, Y, Z) or (R, T, Z) or (R, T, P)—is closest to the surface normal. Next, the software picks the coordinate system direction that follows the previously selected direction. For example, if the X direction is closest to the surface normal, the software selects the Y direction. Or, if the Z direction is closest to the surface normal, the software picks the X direction. The projection of this direction onto the surface is defined as Material Direction 1.
 
* For curved surfaces, the axis of the coordinate system closest to the surface’s normal direction may vary from one location on the surface to another. In this case, it is not recommended to use the Projected Closest Axis option.