GiD_Info parametric
This command returns geometric information (coordinates, derivates, etc.) about parametric lines or surfaces.
For lines it has the following syntax:
GiD_Info parametric ?-no_model? line <entity_id> coord|deriv_t|deriv_tt|t_fromcoord|t_fromrelativelength|length_to_t <t>|<x> <y> <z> ?<t_seed>?
And for surfaces:
GiD_Info parametric ?-no_model? surface <entity_id> coord|deriv_u|deriv_v|deriv_uu|deriv_vv|deriv_uv|normal|uv_fromcoord|maincurvatures|uv_projection_z_fromcoord <u> <v> | <x> <y> <z> ?<u_seed> <v_seed>?
If -no_model flag is specified then entities are stored in a special container, it doesn't belong to the model
The result for each argument is:

• • line|surface: Type of entity.
  • <entity_id>: The number of an entity.
  • coord: 3D coordinate of the point with parameter t (line) or u,v (surface).
  • deriv_t: First curve derivative at parameter t.
  • deriv_tt: Second curve derivative at parameter t.
  • t_fromcoord: t parameter closest to a 3D point. It is possible to specify alse the <t_seed>
  • t_fromrelativelength: parameter corresponding to a relative (from 0 to 1) arc length t
  • length_to_t: lenght of the curve until the parameter t (if t=1.0 then it is the total lengh)
  • deriv_u,deriv_v: First partial u or v surface derivatives.
  • deriv_uu,deriv_vv,deriv_uv: Second surface partial derivatives.
  • normal: Unitary surface normal at u,v parameters.
  • uv_fromcoord: u,v space parameters closest to a 3D point. It is possible to specify alse the <u_seed> <v_seed>
  • maincurvatures: return a list with 8 numbers: v1x v1y v1z v2x v2y v2z c1 c2

v1x v1y v1z : first main curvature vector direction (normalized)
v2x v2y v2z : second main curvature vector direction (normalized)
c1 c2: main curvature values

• • uv_projection_z_fromcoord: to get the location u v of a point x y projected in direction z on a surface (the z of the point must not be supplied). It is possible to specify alse the <u_seed> <v_seed>

e.g: set uv [GiD_Info parametric surface $id uv_projection_z_fromcoord $x $y]
Note: The vector derivatives are not normalized.
Example:
in: GiD_Info parametric line 26 deriv_t 0.25
out: 8.060864 -1.463980 0.000000