In order to inspect how closely the generated U-spline matches the source CAD geometry, users can visualize the projection error. The projection error is the distance between the U-spline surface and the CAD geometry surface.
After building a U-spline, to see the projection error rendered as color shading on the U-spline, call
draw uspline id <uspline_id> projection_error
To turn off the color shading, call
draw uspline id <uspline_id> none