Creating Midsurfaces

You can create a midsurface from a pair of faces that are offset from each other or from a set of faces with some offset. This functionality is useful for simulating medial surface representation of thin solids.

This task shows you how to:

Before you begin: Create a 3D shape in the form of a solid feature, volume feature or a solid body.
See Also
About Creating Midsurfaces

Create a Midsurface from Face Pairs

You can create a midsurface from a pair of faces.

  1. From the Transform section of the action bar, click Midsurface .
  2. In the Support box, select the solid feature, volume feature or body.
  3. In the Creation Mode list, select Face Pairs.
  4. Select one or more pairs of faces from which the midsurface will be extracted.

    The selected face pairs appear in the Midsurface Definition dialog box, under the Main Side and Other Side columns.
    Important: These columns become available only after you select a feature in the Support box.
  5. In the Offset ratio box, type the offset value or use the arrows to change the value.

    Important: Value of offset ratio should be between 0 and 1.

  6. Click OK.

Create a Midsurface by Offsetting Faces (Non-Associative Offset)

You can create a midsurface from a set of faces (or extract features) and an offset. This is useful for complex models which may not contain parallel faces to form a pair.

The created midsurface is automatically extrapolated and re-limited to the selected support.

  1. In the Support box, select a solid feature, volume feature or a body.
  2. In the Creation Mode list, select Faces to Offset.
  3. In the Faces To Offset box, select either the faces to offset or the extract features.
    • Face selection: Select one or more faces in the work area.
    • Extract feature selection: Perform one of the following actions from the context menu:
      • Select Insert Operations > Create Extract. The Extract Definition dialog box appears. For more information, refer to Extracting Elements.
      • Select Insert Operations > Create Extract (in tangency). Then, select one or more faces in the work area.
      • Select Insert Operations > Create Multiple Extract. For more information, refer to Extracting Sub-Elements.
  4. In the Computation Mode list, select Manual.
  5. Click Compute Offset beside the Offset box.
    • Offset faces from the selected faces are detected.
    • Minimum and maximum offset values are computed and displayed in the work area with the Min and Max indicators.

    • Average offset value is computed and displayed in the Offset box.
  6. Optional: Click Min or Max indicator in the work area to evaluate the offset parameter.
    The value in the Offset box is refreshed accordingly.
  7. Optional: Right-click Min or Max indicator in the work area and select Remove Min or Remove Max, respectively from the context menu.
    The Min or Max indicators are removed from the current face. They re-appear on the next sequential face with the recomputed Min or Max value.
    Note: The indicators do not appear after they are removed from the last face.
  8. In the Offset ratio box, type the offset value or use the arrows to change the value.

    Important: Value of offset ratio must be between 0 and 1.

  9. Click OK.

    The midsurface is generated.

Create a Midsurface by Offsetting Faces (Associative Offset)

You can create a midsurface from a set of faces (or extract features) and an associative offset.

  1. In the Support box, select a solid feature, a volume feature or a body.
  2. In the Creation Mode list, select Faces to Offset.
  3. In the Faces To Offset box, select either the faces to offset or the extract features.

    Note: For information and tips on face and extract feature selection, refer to the corresponding step in Create a Midsurface by Offsetting Faces (Non-Associative Offset).

  4. In the Computation Mode list, select Automatic.
    This mode uses five rays to compute the offset faces: four rays projected from each corner of the selected face and one from the center.
  5. In the Computation Method list, select one of the following options:
    • Maximum takes only the maximum applicable offset faces into account.
    • Minimum takes only the minimum applicable offset faces into account.
    • Average takes the average of applicable offset faces into account.
  6. Specify a Thickness Threshold.
    The thickness threshold is a length parameter. It represents the maximum distance from the selected faces under which the offset faces are considered for computation.

  7. In the Offset ratio box, type the offset value or use the arrows to change the value.

    Important: The value of the offset ration should be comprised between 0 and 1.

  8. Click OK.
    The midsurface is generated.

  9. Vary the Thickness Threshold and click OK.
    The midsurface is generated at another position.

    Important: Be aware that only five rays (four corner + one center) are used for the calculation of the offset faces. So, in the figure below, offset faces at 40, 60 and 70 are recognized while offset faces at 90 and 120 are ignored.

Create a Midsurface Using a Thickness Threshold

You can create a midsurface according to a thickness threshold.

  1. In the Creation Mode list, select Automatic.
  2. In the Support box, select a solid feature, a volume feature, or a body.
    An automatic threshold value representing the maximum thickness value appears in the Thickness Threshold box.

    By default, the Automatic Thickness Threshold check box is selected, and the value is not editable.

  3. Click OK.
    The midsurface is generated.

  4. Optional: Click OK.
    The midsurfaces are generated.

Create a Midsurface from Ribs

You can create a midsurface from ribs using an existing connected midsurface.

  1. Define the main shell midsurface by following the steps from 1 through 7 from Create a Midsurface from Face Pairs.
  2. Select the Create a new rib midsurface after OK check box.
  3. Click OK.
    The Midsurface Definition dialog box appears again with Limiting midsurface box containing the main shell midsurface.
  4. Select the required mode of midsurface creation in the Creation Mode list.
  5. Depending on the mode you selected (either Face Pairs or Faces to Offset), follow the steps from the appropriate tasks above to select the faces from the rib.

    Important: During the midsurface creation of ribs, offset ratio is set to 0.5 by default.
    Tip: If your model contains ribs that are crossing each other, it is preferable to select all the faces from a rib before selecting faces from the crossing rib.

  6. Click OK.
    The rib midsurface is generated with the main shell midsurface acting as a relimiter.