Creating a Sketch from Scan from a Mesh


This task will show you how to retrieve basic primitives (line, circle, ellipse) from the free edges of a mesh.
Those primitives are created as sketches.
Please refer to Creating a Sketch from Scan for the global operating mode (Constraints, Primitives, split points, ...).
The command recognizes the free edges of the mesh and will process them as scans,
but since free edges of meshes are not necessarily planar, recognition of basic primitives might be impossible or difficult.
Therefore, you are offered the possibility to define a plane on which the free edges are projected as planar scans,
that can be then processed to sketches.
You can also select the free edges you want to process.
Open the SketchFromScans02.CATPart from the samples directory. 
  1. Click Sketch from Scan .

  2. The Sketch from Scan dialog box is displayed.

  3. Select the mesh. A message warns you that there is at least one non planar scan.
    Click OK in the message box.

  4. The name of the mesh is displayed in the Element field, and the icon becomes available.
    The free edges of the mesh are highlighted as scans in the 3D Viewer.
    Constraints are proposed for these scans.
    The free edges are all labeled V, meaning they will be processed.
    A first plane is proposed.

  5. Use the contextual menu to de-select the free edges you do not want to process.
    The green V turns to a red X.


  6. If you have a closer look at one free edge

    you can see it is difficult to recognize a basic primitive from it.
    Therefore the command computes a median plane (see previous picture)
    and projects the free edges on it, creating thus planar scans from which primitives can be retrieved.
    However you may want to edit this plane:
    click in the dialog box or Edit plane from the contextual menu of the plane.
    The Plane dialog box is displayed.

    You can define a plane:

    • by its origin and its normal,
    • by a brush selection:
      A brush is displayed as a circle,

      Drag it over the mesh, this selects triangles that turn red.

      Now click Init with brush selection. A new median plane is computed from those triangles.
    • by selecting an existing plane:
      Select the existing plane and then click Init with plane selection.
  7. The scans are projected onto the newly defined plane.
    The operating mode is now the same as for standard scans.