Surface Workbench/zh

Introduction
The Surface Workbench introduced in FreeCAD 0.17 provides tools to create and modify simple NURBS surfaces. These tools have a similar functionality to the tool when the  option is used. However, unlike that tool, the tools of the Surface Workbench are parametric and provide additional options. In this respect, the tools in this workbench are similar to and.

Some of the features provided are:
 * Creation of surfaces from boundary edges.
 * Alignment of the curvature from neighboring faces.
 * Constraining of surfaces to additional curves and vertices.
 * Extension of faces.
 * A mesh can be used as a template to create spline curves on its surface.



Usage
The Surface Workbench intends to create faces with shapes, which is not possible to do with the standard tools in other workbenches. The OCCT kernel gives as example a rectangular box with a rounded corners of different radii.



The Surface Workbench integrates with other workbenches of FreeCAD. The above example was created from placed on  in the  PartDesign Workbench. The design can be fully parametric if all datum planes and sketches are defined accordingly. In most cases it is sufficient to draw a closed sketch to define the boundary of a face, and then use different options to further modify its shape.

As of FreeCAD v0.17, the generated surface cannot be placed inside a. However, the generated surface can be contained inside a together with the associated  that holds the datum planes and sketches. The non parametric tool can then be used in order to create a shell and finally a solid.

Tools

 * Surface_Filling.svg Filling: fills a series of boundary curves with a surface. The surface can be modified by adding constraint curves and vertices. The surface changes its shape so that the surface goes through the added constraint elements.
 * Surface_GeomFillSurface.svg Fill boundary curves: creates a surface from two, three or four boundary edges. Three different filling modes are available: Stretch, Coons, Curved.


 * Surface_Sections.svg Sections: creates a surface from edges that represent transversal sections of surface.
 * Surface_ExtendFace.svg Extend face: extrapolates the surface at the boundaries with its local u-parameter and v-parameter.
 * Surface_CurveOnMesh.svg Curve on mesh: create approximated spline segments on top of a selected mesh. If the object is not a Mesh, but a parametric Shape, it must be converted to a mesh using.