The Thickness Grid (which is exportable by right clicking on a mesh or Output Volume) does not calculate the true thickness but rather the vertical thickness.
- A regular grid of points is generated directly above the volume
- The points are projected down onto the top of the volume
- The point is projected to the base of the volume
- The distance vertically from the coordinate where the point is located on top of the volume to where the point is located on the bottom of the volume is calculated
- The vertices are surfaced to produce a mesh which sits at zero elevation when imported back.
This process produces good results for planar volumes because the thickness is calculated from above