About the Modify Shape User Interface
The Modify Shape tab consists of commands and shortcut menus. Click > 
Modify Shape and select a surface to open the Modify Shape tab.
Modify Shape and select a surface to open the Modify Shape tab.Commands
• Mathematical properties
◦ Type
▪ Spline—Controls only the number of segments. Increase the number of segments to achieve a better fit and projection, and better matching for position or tangency constraints. Use this surface type for organic shapes and constrained surfaces, for example, fillets.
▪ Bezier—Controls only the degree of the polynomial. Increase the degree for a better fit. This surface type is not suitable for constrained surfaces. Use this surface type for large and smooth surfaces.
▪ B-spline—Controls both the degree of the polynomial and the number of segments. When you set a lower degree and more segments, you create a surface similar to a Spline surface. When you set a higher degree and fewer segments, you create a surface similar to a Bezier surface.
 | A B-spline surface with two segments (params) in both U- and V-directions is a Bezier surface. |
◦ Segments—Configures the number of segments along the U and V directions.
◦ Degree—Configures the degree of the polynomial in the U and V directions.
• Control point motion commands
◦ Move—Constrains point movement:
▪ Normal—Moves selected points along their own surface normal. The surface normal adjusts to the new point location.
▪ Normal Constant—Moves selected points along the surface normal of the dragged active point.
▪ Normal Orig—Moves selected points along the original surface normal. The surface normal is not affected by previous moves to point location.
▪ In Surface—Moves selected points parallel to tangent plane. Each point moves along its own tangent surface.
▪ Along Bar (Shift)—Moves selected points along their adjoining row or column bar. Hold down SHIFT while dragging to apply Along Bar motion, regardless of the method displayed in the Move box.
▪ In View (Alt)—Moves selected points in a plane parallel to the current view. Create custom views to move points in specific planes. Hold down ALT while dragging to apply In View motion, regardless of the method displayed in the Move box.
◦ Filter—Constrains the distribution of selected points surrounding the active point:
▪ 
—Moves points the same distance as the dragged active point. For a constrained surface, the boundary does not move.
—Moves points the same distance as the dragged active point. For a constrained surface, the boundary does not move.▪ 
—Uses a linear equation to define point motion. The distance decreases in proportion to the distance from the dragged active point.
—Uses a linear equation to define point motion. The distance decreases in proportion to the distance from the dragged active point.▪ 
—Uses a quadratic equation to define point movement. Motion of the selected points drops off smoothly with the distance from the dragged active point.
—Uses a quadratic equation to define point movement. Motion of the selected points drops off smoothly with the distance from the dragged active point.◦ Adjust—Moves a selected control point. (The active point is surrounded by a red circle.) Type a value and use the arrows to move a selected control point.
The following commands set the visual display of changes made to the surface:
• 
—Displays a translucent or opaque preview of the modified surface.
—Displays a translucent or opaque preview of the modified surface.• 
—Displays a control mesh to use when modifying the surface shape. A glyph near the control mesh corner indicates the U and V parametric directions of the surface. U indicates the direction of the rows, and V indicates the direction of the columns.
—Displays a control mesh to use when modifying the surface shape. A glyph near the control mesh corner indicates the U and V parametric directions of the surface. U indicates the direction of the rows, and V indicates the direction of the columns.• 
—Displays knot lines to use when modifying the structure of the control mesh.
—Displays knot lines to use when modifying the structure of the control mesh.Shortcut Menus
There are three Modify Shape shortcut menus:
• Surface Menu—Right-click the surface being edited. Select a command to add or remove segments, modify the degree of the polynomial, change the move point option and filter, or to clear all boundaries.
• Boundary Menu—Right-click a selected surface boundary. Select a command to preserve or change existing constraints, deselect all points, or change the move-point settings.
• Glyph Menu—Right-click the glyph. Select a command to change the move-point method, or filter.