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    Using CAD
    Description format surfaces

    CAD-functions for surfaces:

    A planar Surf. (Trim / punch)
    Planar surface; unperforated or perforated

    Input: boundary [islands ...]
      The curves used for boundary and islands must be closed;
      use circle, ellipse, closed B-Spline, closed polygon
      or closed CCV.

    Output:
    A = boundary curve [islands ...]

    # Example circular surface:
    C20=P(0 0 0) 10
    A20=C20

    # Example Planar surface:
    P20 = P (-120 -160)
    # The boundary curve:
    S20 = CCV P20 P (233 -186) P (223 -95) P (104 -81) P (135134) P (-122 162) P20
    # The planar surface:
    A20 = S20

    # Example: outer edge C29, island C28.
    C29 = P (-252.2 -580.9 0) VAL (12)
    C28 = P (-255.9 -606.8 0) VAL (66)
    A20 = C28 C29

    A spheric.Surf (Axis, wheel) SPH
    Spherical surface

    Format:
    A = SPH axis radius [rotAngle1 rotAngle2 [height1 height2]]
       Axis:      The main axis and the center of the sphere
       Radius:    KeyIn radius or sel point on sphere
       rotAngle1  KeyIn angle (Def = 0) or sel. point.
       rotAngle2  KeyIn angle (Def = 360) or sel. point.
       tiltAngle1 KeyIn angle (Def = 0) or sel. point.
       tiltAngle2 KeyIn angle (Def = 180) or sel. point.

    # Example:
    P20 = P (68 68.9 0)
    A21 = R SPH (P20) 12

    A cylindr.Surf (Axis, radius)       CYL
    Cylindrical surface

    Format:
    A = CYL axis radius rotAngle1 rotAngle2 height1 height2
       Axis:     The main axis of the cylinder; line, vector or plane (z-axis).
       Radius:   KeyIn radius or sel point.
       rotAngle1 KeyIn launch angle (Def = 0) or sel point.
       rotAngle2 KeyIn End piece (Def = 360) or sel point.
       height1   KeyIn elevation (from Achsstartpunkt; Def = 0) or sel point.
       height2   KeyIn elevation (from Achsstartpunkt) or sel point.

    # Examples:
    L1=P(0 0) P(100 0)
    A1=CYL L1 12 0 360 0 30

    R2=PERP P(105 129.2 0) D(1 1 1)
    A2=CYL R2 12 0 180 0 30

    A Revolved S. (Axis Contour) SRV
    Revolved-Surface
      Rotate contour-object around axis
      Contour is roughly paralllel to the axis (normal: Sweep-surface)

    Format:
    A = SRV axis contour [Start1 End1 [Start2 End2][CW]]
       Axis        Line or Plane or PT+PT or PT+LN or PT+VC
                   Circle: axis from centerpoint and normalvector
       Contour     line (cone), circle (torus) or B-Spline.
       Start1      Startpoint revolved-surface: angle (Def = 0) or point.
       End1        Endpoint revolved-surface: angle (Def = 360) or point.
       Start2      Startpoint contour: parameter (Def = 0) or point.
       End2        Endpoint contour: parameter (Def = 1) or point.
       CW          sense of rotaion of revolved-surface: def =CCW
                   (counterclockwise); CW is clockwise.

    Examples:
    # cone:
    L20 = P (20 0) P (20 20)
    L21 = P (50 0) P (40 20)
    A20 = SRV L20 L21 270 0

    # torus:
    P20=P(-30 -10 0)
    P22=P20 X(100)
    C20=P22 20 DY
    P23=P20 Y(100)
    P24=P20 Y(-100)
    A20=SRV L(P20 DZ) C20 P22 P23 #CW

    A Extrusion Surf (Contour Vec)           SRU
    Extrusion surface from basic element and vector:
       Basic Element: LN / AC / CV
       Vector:        vector or PT-PT or LN ..

    # Example:
    L30 = P (0 -10 20) P (0 10 20)
    D30 = D (10 10 60)
    A30 = SRU L30 D30

    A Sweep Surf (Contour Path)              SWP

    Surface from path (spine) and contour;
      eg pipe from moving a circle (contour) along a line (path).
      The contour always is on a plane normal to the path.
      With heavy curvature of the spinecurve overcuts are possible.

      Contour:       circle, ellipse, polygon.
      Path:          line, circle, ellipse, spline.

    # Example:
    P20=P(30, -4280, 0)
    P21=P20 Z(2000)
    L20=P20 P21
    P23=P(900 -3177 0)
    S21=ELL P20 P23 P(-142 -3537 0)
    S20=POL P20 P(645 -5272 0) P23 P20
    A20=SWP S20 L20
    A21=SWP S21 L20

    A Loft Surf (Curves across)              BSP
    Free-form area from cross section curves.

    Curves across [BSP]
      Select (at least 2) cross section curves
      The first and the last curve are the boundaries.
      Curves can be lines, circles or b-spline-curves.
      The first and/or last inputobject may be a point.
      Continue with tab-key.
      Finish with Enter-key.

        With the function "S BSpline < join obj's" you can join
        pieces to one connected cross-section-curve.

    # Example:
    L20=P(-100 60 0) P(-100 30 0)
    L21=P(-50 60 0) P(-60 80 0)
    C20=ARC1 P(-20 100 0) P(0 90 10) P(20 80 0)
    P20=P(-130 40 0)
    P21=P(30 120 0)
    #
    A20=BSP U(P20 L20)
    A21=BSP U(L20 L21)
    A22=BSP U(L21 C20)
    A23=BSP U(P21 C20)

    Example models:
       Sample_area_bsp0
       Sample_area_bsp4
       Sample_area_bsp6

    A Loft Surf (Curves along/across)        BSP
    Free-form area of horizontal and vertical sectioncurves.
    The first and the last curve are the boundaries.
    All length-wise and cross-wise curves must be a network.
    Inputcurves can be points, lines, circles, polygons,  b-spline-curves.
      (currently not CCV-composite curves).

    If the horizontal sectioncurves meet in a point,
      this point can be selected as first or last vertical curve.

    Curves along [BSP]
      Selectieren (at least 2) length-wise curves
      Continue with tab-key.

    Curves across [BSP]
      Select (at least 2) cross-wise curves
      Continue with tab-key.
      Finish with Enter-key.

    Example (2 curves along; (Spline S20, Line L20);
      3 curves across (Point L20, Line L21);
      The curves-along form a tip in point P20.
      Die Längskurven bilden im Punkt L20 eine Spitze.

    P20=P(-56 -18 0)
    P21=P(25 4 0)
    P23=P21 Z(4)
    L20=P20 P23
    L21=P21 P23
    S20=BSP P20 P(-30 -20 0) P(1 -11 0) P21
    A20=BSP U(S20 L20) U(P20 L21)

    Sample models:
       Sample_area_bsp3 (5 x 4 curves)
       Sample_area_bsp5 (2 x 1 edge curves)
       Sample_area_bsp7 (2 x 2 boundary curves)

    A trimmed supported punched FSUB
    Space at Support area limited, perforated or unperforated.

    Format:
    A = FSUB Support-area boundary-curve [islands ...]
       Support-area: Spherical, cylindrical, revolved, Extrusion or loft surface
         or cone or torus;
       boundary-curve, Islands:
         circle, ellipse, Spline, polygon or contour (CCV).
         boundary-curve and islands must be closed.

    The boundary curve must be based on the Support area.
    If the outer contour of the support-area is identcal with the boundary-curve,
      then the name of the support-area can be used for the boundary-curve.

    A = FSUB A S                support-area, trimmed
    A = FSUB A S S              support-area, trimmed, 1 hole
    A = FSUB A A S S            support-area, not trimmed, 2 holes

    A = FSUB B S                cone or Torus, trimmed
    A = FSUB B S S              trimmed, perforated
    A = FSUB B B S              not trimmed, perforated

    Examples:
    # cone surface:
    P20 = P (100 0 0)
    P21 = P (200 0 0)
    P22 = P20 Y (120)
    P23 = P21 Y (60)
    P24 = P20 P22 ANG (135) DX
    P25 = P21 P23 ANG (135) dx
    C20 = ARC P23 P25 P21 dx
    C21 = ARC P22 P24 P20 dx
    # The body:
    B20 = CON C21 C20
    # The boundary curve:
    S20 = CCV P23 P22 C21 P24 P25 C20 P23
    # The cone surface:
    A20 = FSUB B20 S20

    P26=P(250 -750 0)
    S21=REC P26 D(500 0 0) D(0 200 0)
    A21=S21
    P27=P(510 -660 0)
    C22=P27 40
    C23=P27 80
    A22=FSUB A21 C23 C22

    A Hatch / hatch         HAT
    Hatched surface

    Format:
    A # = HAT boundary-curve interval direction
       boundary-curve    circle, ellipse, Spline, polygon or contour.
         boundary-curve must be closed.
       interval          distance of the hatch lines
       direction         angle of the hatch lines in degrees

    Example:
    P20 = P (-500 500)
    S21 = CCV P20 P (400900) P (400300) P20
    A20 = HAT S21 VAL (50) VAL (45)

    Currently, no import / export function for hatching.
    Currently no function for perforated hatches.