Modeling with Subdivision Surfaces/ Using the Knife tools 

Using the Knife tools

The SDSPlus plugin must be installed to be able to use these tools.  Two knife tools are available: the Object Knife Tool and the Freehand Knife Tool.

Object Knife tool

You can use the SDS Object Knife tool to create new points and edges to selected SDS objects. The surface of the last selected object is used as a knife to cut the selected SDS objects. New vertices are added to edges where the edges pass through the surface of the knife object.  

 
A Nurbs suface (knife) passing through rectangular SDS mesh. 

 
The Knife tool applied.   
 

Note: You can find this tool from the 'SDS' tab of the default working environment.  

The tool has the following options:  

  1. Selected - if checked only the selected edges are affected 
  2. Add edges - new edges are added between the new vertices
  3. Select - which faces to select. The SDS object must be in face selection mode.

    4. The values are:  
    No selection - does not change selection  
    Inside - select faces whose center point is inside the knife object  
    Outside - select faces whose center point is outside the knife object 

Freehand Knife tool

A curve or a line segment can be drawn defining a surface used as a knife. New vertices are added to edges where the edges hit the surface of the knife. This tool can be activated buy clicking the "Knife" button on the SDS control bar or by selecting the "Methods/Sub Division Surface/Knife" menu item.  

The tool has the following options:  

  1. Selected - if checked only the selected edges are affected. 
  2. Add edges - new edges are added between the new vertices. 
  3. Freehand - if checked a freehand curve can be drawn. Otherwise a line segment can be drawn. 
  4. Select - which faces to select. The SDS object must be in face selection mode. 

    5. The values are:  
    No selection - does not change selection  
    Inside - select faces whose center point is inside the knife object  
    Outside - select faces whose center point is outside the knife object 
  
 
The Knife tool activated and freehand curve drawn over a rectangular SDS mesh 

 
Freehand knife applied.