 # B-spline Surface by Points (3D only) Used to place or construct a free-form B-spline surface.

You can access this tool from the following: • Ribbon: Modeling > Surfaces > Create Surfaces > Construct Surface > By Points
• Toolbox: Create Freeform Surfaces SettingDescription
Method Sets how the surface is generated.
• Control Points — Points (vertices) of the control net are defined by data points or vertices of elements. The number of points (or poles) in the u- and v-direction must be greater than or equal to the order in that direction.
• Through Points — Surface passes through the points defined by the data points or vertices of elements and is interpolated at each point. One pole is defined for each data point, the number of which must be greater than or equal to the Order.
• L-Square By Tol — The surface is approximated based on the points defined by the data points or the vertices of the selected line string or shape. The maximum deviation of the input points from the surface is adjustable using the Tolerance setting. After the approximation surface is created, the maximum deviation and the mean deviation are displayed in the status field.
• L-Square By Num — The sum of the squares of the distances from the data points or vertices of elements to corresponding points on the surface is minimized. The control net has the active number of Poles in the u- and v-direction. If the maximum error exceeds the Tolerance, the maximum error is displayed in the status bar. Tolerance is set in the 3D and B-splines dialog (Element > 3D and B-spline).
• Catmull-Rom — Fourth-order NURBS surface that is interpolated to closely resemble the overall shape defined by the data points entered or vertices of the selected line strings.
Input By Sets how the surface is created.
• Entering Points — The surface is placed by entering data points.
• Picking Linestring — The surface is constructed based on the vertices of line strings.
Closure Sets whether surface is Open or Closed in the u- or v-direction.
Order The order of the equation that defines the surface in the u- or v-direction (2-26).
Poles (Method set to L-Square by Num only) The number of poles in the u- or v-direction.
Keep Original If on, the profiles used for creating the surface are retained in the model.
Key-in: `PLACE` `SURFACE` < `CATMULLROM` | `CONTROLPOINTS` | `LSQUAREBYNUM` | `LSQUAREBYTOL` | `THROUGHPOINTS` >