Creating Laws

You can create evolution laws within a representation. These laws can be used later on when creating Generative Shape Design elements, such as swept surfaces, or parallel curves.

Before you begin: Create a 3D shape containing two curves.
  1. From the Transform section of the action bar, click Law .
  2. In the Reference box, select the line.
  3. In the Definition box, select a curve.
    The law is computed as the distance between points on the reference line and their matching points onto the curve.

    Tips:
    • The laws can be created using negative values. The intersection between the reference line and the definition curve is taken into account to change the law evaluation sign. The direction lets allows you to choose which side of the reference line must be considered as positive.
    • If X parameter on definition is checked, the X parameter is displayed on the selected curve and represents the percentage of the curvilinear abscissa on this curve. The law is computed by projecting the start point normally onto the reference line.
    • You can analyze the law using the handle, or specifying a value in the X box. This parameter represents the percentage of the curvilinear abscissa on this curve. The law is computed by projecting the start point normally onto the reference line. The Y box indicates the distance between any point on the reference line and its matching point on the selected curve.
  4. In the Scaling box, define the law amplitude by entering a value or using the graphic handles.
    When the law is applied to a geometric element, the latter usually is not of the same length as the reference line. Therefore a linear mapping is applied between the reference line and the element the law is applied to, resulting in a scaling of the law.

    In the illustration, the law is applied to a circular sweep (top) and to a parallel curve (bottom). The dotted lines represent the linear mapping between the law (middle) and the two elements to which it is applied.

  5. Select the Heterogeneous Law check box to define the applied law unit (none for ratio law; degree, radian, or grade for angle law) and the distance measure units (current unit by default).
    Two conversions will be performed during the law evaluation:

    • conversion from the model unit (millimeters) to the stored measure unit.

    • conversion from the stored applied law unit to the model unit (degrees) in case of an angle.

  6. Click OK.
    The law is now ready for use in the creation of other Shape Design elements.
  7. From the Wireframe section of the action bar, click Parallel Curve .
  8. In the Parallel Curve Definition dialog box, click Law....
  9. Select Law.1 from the tree.
  10. Click Close.
    The law is applied to the selected element.

    • When the reference line and definition curve do not present the same length, only the common area is used to compute the law.

    • Select Both Sides check box to generate a parallel curve symmetrically on each side of the selected curve. Note that depending on the geometry, the elements may not appear symmetrical. They are if the curve is a line, otherwise, the resulting curves' shape may differ:
      Resulting parallel curves when a line is selected
      Resulting parallel curves when any curve is selected
    • When the X parameter on definition check box is cleared, the selected curve should not present several intersections with the plane normal to the reference line. If there are several intersections, the law cannot be evaluated and cannot be applied when creating geometric elements.
    Important: The laws created using the Engineering Rules Capture app, being mathematical formulas, can be used with Generative Shape Design's operators, such as About Swept Surfaces, Creating Parallel Curves or Creating a Helix for instance. For further information, see 3D Modeling: Multi Discipline Automated Engineering:Engineering Rules CaptureUser's Guide.

    Note that laws created using the Law icon of Generative Shape Design app can be referenced by laws created with Engineering Rules Capture app.

    Important: Selecting a published law from another representation is not allowed.