Retain Offset, Retain Ratio
When you want a portion of the SubD to remain intact when a constraint surface is moved or changed, you can specify which parts of the SubD will be affected. Keeping in mind that SubD elements affect their neighbors, you will want to select one edge loop’s worth of the SubD beyond your target area.
In the image sequence below, the three loops of vertices right under the plane are set to Retain Offset in image A. As the plane moves all of these vertices will move with the plane as seen in figure C and D.
When there are two, roughly parallel, constraining entities, you can choose to have the SubD stretched evenly between the two. As with the Retain Offset option, you must also mark the part of the SubD you wish to be affected. In the image below on the left we set up the Retain Ratio and move the plane. The top image on the right shows the result. The bottom image on the right shows what happens if we only set half of the Retain Offset and the other half to Retain Ratio.
Created with the Personal Edition of HelpNDoc: Easily create HTML Help documents