Modify a spline curve

Description: 5 minutes; Lab exercise: 30 minutes

OneSpace Designer provides powerful CoPilots with which you can manipulate spline curves. Use them to modify splines and make local changes easily.

Note  You may still use the old 3D Curve command by typing (load "old_curve_3d").  Look in $INSTALLDIR\help\osdm\Common\documentation\goodies\Readme-0114 for the documentation. In addition, the multi-view display option is no longer available; it has been replaced by the Point 3D CoPilot.

Improvements include

Fix (or un-fix) interpolation points

Fixed interpolation points limit the area of change on the curve to the segment between the two points; the points appear as orange dots.  The illustration shows the difference between moving an interpolation point between unfixed points (left) and between fixed points (right).  Fixed points may be un-fixed; when you next modify the curve, the spline will be recalculated, updating the shape of the curve.

Easily change or delete tangents

For fine control over the shape of the spline curve, you can attach or modify a tangent vector at any interpolation point.  If a tangent vector exists at a point, you can remove it by toggling off the Tangent option for the selected point.  In modifying a spline, you use the Vector 3D CoPilot to change both the direction and the weight of the tangent.  You may delete a tangent, as illustrated below, either by

Change the start or end condition of curves with respect to other edges or faces

The End Condition of a curve may be changed.  The default option is Position.  If you choose the Edge or Face option, the connection condition dialog opens.  You may choose Closed to create closed splines.  If you change an End Condition from Closed to Position, OSDM will delete the segment of the spline you specify, open the curve, and fix the two end points of the curve.

Easily specify control and interpolation points

When creating 3D curves, OSDM prompts you to specify where you wish to place a point.  3D CoPilots assist you to position the points accurately, and 3D curve menus give you easy access to:

Menu options

Mode

Mode allows you to choose between Interpolation and Control modes. Interpolation mode allows the use of interpolation points and tangents.

Both modes allow the options to Append, Move, Delete, and Insert points.  In Interpolation mode, you have the options to Change, or Delete a tangent, to specify an End Condition, and to fix and un-fix points - (Un-)Fix Pt.  

Note  Switching from interpolation to control mode will delete information about fixed points and tangents.

Undo

The Undo button will remove the last change you made; if grayed out, no further reversals are available.

Follow Me

Follow Me will cause the 3D CoPilot to follow your cursor.

Feedback

Feedback displays curvature feedback as you move the cursor.

 

Lab exercises

These exercises provide hands-on experience using the Modify 3D Curve feature in OneSpace Designer Modeling 2005.

Prerequisites

Append to a curve

Start OneSpace Designer Modeling and load append_spline.pkg.  You will see three 3D curves parts: ip has a Fix Point at the end point; cc was created without a tangent condition at the end point and therefore has a curve continuous condition at the end point; and tc has a tangent condition at the end point.  As you append to each curve, notice the differences among these conditions.

  1. Append to a curve with a Fix Point at one end.
    1. Click 3D Curve .
    2. Click Spline in the Modify section.
    3. Click Follow Me in the dialog.  
    4. Click curve ip.  Notice the Fix Point at the end on the right.
    5. Click Append.
    6. Click the Fix Point.  

       
    7. Click a point to the right of the curve as shown above.
    8. Click to complete the operation:



       
  2. Append to a curve with a tangency condition.
    1. Click Spline in the Modify section.
    2. Click curve tc.  Notice the blue arrow indicating a tangent condition at the end point on the right:

    3. Click Append.
    4. Click Follow Me in the dialog.  
    5. Click the end point of the curve.

    6. Click a point to the right of the curve as shown above.
    7. Click to complete the operation.

  3. Append to a curve with a curvature continuous condition at the end.
    1. Click Spline in the Modify section.
    2. Click curve cc.  Note that although this curve was created with a curvature continuous condition at the end, the orange arrow is not shown.
    3. Click Follow Me in the dialog.  
    4. Click Append.
    5. Click the end point to the right.

       
    6. Click a point to the right of the curve as shown above.

    7. Click to complete the operation.

       

Insert an interpolation point

  1. Start OneSpace Designer Modeling and load adjust_2_bsplines.pkg.

  2. Click 3D Curve .

  3. Click Spline in the Modify section.

  4. Click anywhere on bspline2 to select the curve. OSDM highlights the curve and its three points.

  5. Leave the Mode at Interpol.  If you haven't turned on Follow in the Settings menu, click Follow Me in the dialog.

  6. Click Insert.  The prompt line displays, "Specify segment."

  7. Click between the point at the top and the middle point to select the segment between them.

  8. Use the Point 3D CoPilot to position the new point somewhere in the Viewport and observe the resulting shape of the curve.

      

  9. Click Undo.

  10. Click (Un-)Fix Pt.

  11. Click the middle interpolation point on bspline2 to create a Fix Point.

  12. Click Insert.  

  13. Click between the point at the top and the middle point to select the segment between them.

  14. Use the Point 3D CoPilot to position the new point somewhere in the Viewport and observe the different shape of the curve.

      

  15. Click to complete the operation.

The shape of the spline changes in response to your new interpolation point.

Change a tangent

  1. Start OneSpace Designer Modeling and load adjust_2_bsplines.pkg.

  2. Click 3D Curve .

  3. Click Spline in the Modify section.

  4. Click anywhere on bspline1 to select the curve.  OSDM highlights the curve and its three points.

  5. Leave the Mode at Interpol.  If you have not turned on Follow in the Settings menu, click Follow Me in the dialog.

  6. Click Change Tan.

  7. Click the interpolation point midway on the curve.

  8. Use the Vector 3D CoPilot to change the direction of the tangent. (Right-click to Accept the new tangent.)

       

  9. Click to complete the operation.

The curve changes to reflect the new tangent.

Change an end condition

  1. Start OneSpace Designer Modeling and load adjust_2_bsplines.pkg.

  2. Click 3D Curve .

  3. Click Spline in the Modify section.

  4. Click anywhere on bspline1 to select the curve.  OSDM highlights the curve and its three points.

  5. Click the End Condition drop-down menu and select Edge.

  6. OSDM prompts you to select an endpoint of the currrent curve.  Click the free end of bspline1.  The Condition menu opens.

  7. Click bspline2 to specify the edge.

     

  8. Click Flip Pos and Flip Dir to change the resulting curve.  

  9. Click Abort to return to the Modify Spline menu.  

  10. Click the End Condition drop-down menu and select Closed.

     

  11. OSDM closes the bslpine1 curve.

  12. Click to complete the operation.

 

Limitations