PK_TOPOL_fctab_curv_dirs_t

struct PK_TOPOL_fcstr_curv_dirs_s
       {
       PK_VECTOR_t  principal_direction_1;
       PK_VECTOR_t  principal_direction_2;
       double       principal_curvature_1;
       double       principal_curvature_2;
       };
typedef struct PK_TOPOL_fcstr_curv_dirs_s
               PK_TOPOL_fcstr_curv_dirs_t;
struct PK_TOPOL_fctab_curv_dirs_s
       {
       PK_TOPOL_fcstr_curv_dirs_t *data;
       int                         length;
       };
typedef struct PK_TOPOL_fctab_curv_dirs_s
               PK_TOPOL_fctab_curv_dirs_t;

Used in:

PK_TOPOL_facet_table_t

This is a support structure for PK_TOPOL_facet_2_r_t. It is an indexed table
of the principal directions and curvatures of the face.

If the principal curvatures are equal (in both sign and magnitude) then the
principal directions are not significant.

Maximum and minimum curvatures are returned as the principal curvature values.
The principal curvature with the smallest absolute value is always returned as
'principal_curvature_1', irrespective of whether it represents the maximum or
minimum curvature. Likewise the principal curvature with the largest absolute
value is returned as 'principal_curvature_2'.

The sign of the curvature is positive if the face curves away from the
face normal direction.