|
Managing the tangent vector |
Scroll |
When plotting a spline on a surface, you can control its shape by modifying the parameters of the tangent vectors at the points of the spline.
If a spline is plotted by vertices then you can modify the tangent vector in any point. If a spline is plotted by poles, you can only modify the tangent vector in the terminal points.
Select the spline customization point in the graphic area or in the point parameters table (to select a point in the graphic area, first switch to editing pipeline).
Expand the group of elements Shape Management and click the Parameters button 
in the Method button group. The controls to set up the tangent vector will appear on the Parameter Toolbar.
Setting up a spline by vertices
If a spline is plotted by vertices, then a phantom of the tangent vector is displayed in the graphic area when you set up the parameters of this tangent vector.
You can set the direction and the length of the tangent vector. To select a direction, use the Tangent Direction group of controls.
The following options are available.
By vector — the vector direction is determined by an arbitrary angle.
Enter the angle of the tangent vector in the Angle field, enter the Length in the Length field. You can also set the direction and the length of the vector by moving the point at the end of its phantom in the graphic area.
Direction U or 
Direction V — the vector is located tangentially to the isoparametric curve U/V of the face on which the spline is being constructed.
Set the length of the tangent vector. To do this, enter the required value in the Length field or move the point at the end of the phantom of the tangent vector in the graphic area.
If needed, you can reverse the direction of the tangent vector using the Reverse Direction 
button located next to the Length field.
When the parameters of the tangent vector are modified, the phantom of the spline in the graphic area is rebuilt.
Setting up a spline by poles
If a spline is built by poles, you can only modify its shape in its terminal points. In this case the position of the point adjacent to the terminal point is restricted. This restriction is determined by the position of the tangent vector in the terminal point.
Points with applied constraints are marked with a special icon
in Point parameters table. These points may be displaced as long as the mating condition is satisfied.
To modify the shape of the spline in a point, select the direction of the tangent vector in this point. To do that, use the buttons in ther Tangent Direction group.
The following options are available.
By Vector — the vector direction is determined by an arbitrary angle. Enter the angle of the tangent vector in the Angle field.
Direction U or Direction V — the vector is located tangentially to the isoparametric U/V curve of the face on which the spline is constructed.
After the direction of the vector in the terminal point is modified, the adjacent point moves and the phantom of the spline is rebuilt.
|
A point adjacent to a terminal point can be linked to a point object. In this case, you can only set the Direction U or the Direction V for the tangent vector if the link is removed. After you select a direction, a message will appear on the screen. You can delete the link in this message. To proceed with setup, press the Edit button. The link of the point to the point object will be deleted, the position of the point and the shape of the spline will change. To cancel plotting, press the Cancel button in the message. |
See Also
