Varying the Section of a Spined Surface

When creating a Spined Surface starting from just one boundary and no or just one drive, you can define the way the section of the surface varies along the path.
 
1 In the Variation drop-down list select the type of variation to be applied to the section of the surface (initially = boundary) along its path:
Angle to vary the section by rotating it through an angle according to the law specified in the Law drop-down list
Scale to vary the section by a scale factoraccording to the law specified in the Law drop-down list. enter the scale factor into the Last box (>1 enlarges, <1 reduces).

2 In the Law drop-down list select the variation law to be applied to the section along its path:
Linear to vary the value linearly from the First value to the Last one. Enter the values into the two boxes.
Parabolic to vary the value parabolically from the First to the Middle and then to the Last one.

See the following examples.

 

Varying the angle

In the same example used in Creating a Spined Surface from one boundary and one drive let us now vary the angle.
 

  1. In the Variation drop-down list select Angle.
     
  2. In the Law drop-down list select Linear. The following preview is displayed:


     
  3. In the First box, leave the value 0. Enter 15 into the Last box.



    The following illustration displays what happens when you press the TAB key: a rotation of 15º is applied to the section


     
  4. You can change the values as you like. Updated previews are immediately displayed:


     
  5. If you change the Law to Parabolic, the Middle box is displayed. Enter a value to see what happens.

 

Varying the scale

In the same example used in Creating a Spined Surface from one boundary and one drive let us now vary the scale.
 

  1. In the Variation drop-down list select Scale.
     
  2. In the Law drop-down list select Linear. The following preview is displayed:


     
  3. In the Last box enter 2. The section is enlarged.



    If you enter .5 instead, the section is reduced:


     
  4. If you change the Law to Parabolic, the Middle box is displayed. Enter a value to see what happens.



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