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The Pwr_Surface tool is like the Pwr_NURBS tool in that it gives you the ability to modify parameters of many surfaces at one time.  You can modify the display settings and the Power Surface parameters in the dialog shown above. 

  Surface Definition Type  

Adaptive:  This option will perform an adaptive creation of the surface to the specified 3-D Tolerance and Angle Tolerance settings specified below.
Uniform Adaptive:
  Utilize the smallest knot distance from the adaptive algorithm to control the knot spacing.
Number of Curves:
  Choose this option if you want to designate a number of controlling curves as specified in the "Number Curves" setting below.
Use Rail Knots:  The solution produce a surface using rail knots along the rails.
Adaptive Knots:  Use the Rail knots and also perform additional subdivision to achieve the desired 3-D Tolerance and Angle Tolerance specified below.

  Surface Parameters  

3-D Tolerance:  The tolerance distance used to determine edge connectivity.   
Angle Tolerance:  Angle tolerance in degrees between two surfaces being made tangent.
Number Curves:
  The number of curves to use in defining the surface.
Flip Surface Orientation: If TRUE flip the normal (direction) of the surface by swapping the UV directions.  Use this option if the surface is facing the wrong direction.
Surface Splitting: This controls when surfaces are split into separate faces.

  • No Splitting - surface are never split even if they have a crease. Note that if you plan to use the surface in subsequent Boolean/fillet/trimming operations you should not use this setting.
  • Allow G1 Surfaces - splits surfaces only if they have a crease in them.
  • Allow C1 Surfaces - splits surfaces along any iso-curves that are not at least C1 continuity.
  • Split At All Knots - splits surfaces along every iso-curve where there is a knot.
  Step Back Blending Options  

Step back blending is a fast and easy way to construct blends along breaks in discontinuity for constructed surfaces.  The blends will step back along an isoperimetric curve of two adjacent surfaces.  For example the sweep of a box would produce 4 edges with discontinuities.  The Step-Back blending is a way to round those corners without going back and putting fillets/blends on the original shapes.    

Blend None:  Don't do step-back blending.
Blend Corners: Do blending along sharp edges.
Blend All: Not Implemented.



Linear:  Make a line between step back curves.
G1 Blend Section:
Make a G1 blend between step back curves/surfaces.
G2 Blend Section:
Make a G2 blend.
G3 Blend Section:
Make a G3 blend.

  Step Back Blending  

Step Distance %:  How far relative to the size of the object to step back from the original corner.  Note that this will be an average distance.
Blend Strength: Relative strength of the blend.  Higher strength produces a tighter blend corner and lower strength flattens the blend out. 

  Trimming and Extending  

This panel allows users to step back (trim) or extend the boundaries of a surface. Note you can easily experiment with these values to determine which parameter in U or V correspond to which edges of a surface.

U:  Minimum and maximum U parameters for Trim/Extend.
V:  Minimum and maximum V parameters for Trim/Extend.

Extension Type: There are several extension types to choose from:
G1_Tangent_Extension, G1_Ruled_Extension, G2_Curvature_Extension, and G3_Extensions. The higher G2 and G3 extensions will extend the surface keeping a higher continuity but have the side effect that they may look stranger when the extension distance is somewhat larger (i.e. more than 50% outside of the original boundary). The G1 extension types tend to behave better at larger extension values.

Note:  these values are available for dynamic editing through the right mouse subobject editing menus for Pwr_Blend, Pwr_RailSweep, and Pwr_CrnrBlnd.  From the right mouse Quad menu, choose the "UV Trimming" option to begin editing.  The UV trimming values can be conveniently edited by selecting the large green rectangles shown on the edges of the surface.  Moving them allows you to dynamically trim back the surface. You may also edit the shape of the trimming boundary by pulling on the control points of the UV Boundary Curves which are the smaller of the green rectangles. Each boundary is defined by a 4 point NURBS curve. See below for examples:

Trimming Boundary Using Large Trim Boxes

Trimming Boundary Using Corner Control Point

Trimming Boundary Using Interior Control Point