KOMPAS-3D v25

Surface adustment of polygonal objects: overview

The Surface ajustment command is used to perform an adjustment.

Procedure

1.Select a portion of the surface of a polygonal object, or select the entire object.

•To select an entire object, click on it in the graphics area or select it in the Design Tree. All triangles that make up the surface of the polygonal object will be selected.

•To select a segment of the object's surface, click on that segment with the mouse in the graphics area. All the triangles that make up the segment will be selected.
Segment selection is available only for objects whose surface has been divided into segments, for example, as a result of using the Segmentation of a polygonal object command or when creating a polygonal object by importing from JT files. Such objects cannot be selected in their entirety. The surface is constructed using one of the segments.

•To select a custom area of the surface, click the Select Triangles button to the right of the Object field. The triangle selection subprocess will start. Select all the triangles that make up the desired section, and click the Create Object button. The system will return to the surface fitting process.

After specifying a surface for fitting, the Object field in the Parameter Panel will display the number of triangles that make up that surface.

2.Specify the type of surface to be inscribed within the specified area. Use the Surface Type list to do this.
By default, the Auto-deterination option is selected in the list. When a section is defined, the system automatically selects the surface type that best matches the resulting set of triangles. The corresponding entry in the Surface Type list is highlighted. The system determines the parameters for the selected surface type in such a way as to minimize the deviation of the resulting surface from the original data.

If necessary, you can manually select the surface type from the list. The system will calculate the parameters for the selected surface. Manual selection is possible both before the surface type is automatically determined (i.e., before specifying the area for approximation) and after. Learn more about specifying the surface type...

After selecting the surface type, a phantom of the surface being created appears in the graphics area.

3.If necessary, specify a guide object. This will allow you to align the surface being created with the objects already in the model.
When creating a flat surface, the guide object defines the direction of the normal; when creating a cylinder, cone, sphere, or torus, it defines the direction of the axis. For a spline surface, specifying a guide object is not available.
You can specify the following as a guide object:

•a straight object — the object itself is used to level the surface,

•flat object — the normal to the object is used to align the surface,

•an object with an axis of rotation (cylindrical face, conical face, etc.) — the object's axis is used to align the surface,

•Create a vector—the object itself is used to align the surface.

The name of the object specified as the guide is displayed in the Guide Object field.

4.For certain types of surfaces, you can view and modify parameters; for example, for a conical surface, this is the slope, for a cylindrical surface, it is the cylinder radius, and so on. The Parameter Panel contains fields that display the values of these parameters, which are automatically determined by the system.
To change a parameter value, set the Manage Parameters switch to the I (On) position and enter the desired value in the field.

5.If the specified surface region is not closed and Cylinder, Cone, or Torus is selected in the Surface Type list, the Close option appears on the Parameters panel. Enable this option to construct a closed surface of the selected type based on the approximation results of the specified region. This may be necessary when it is not possible to specify all the required surface triangles (for example, if other model objects interfere with the specification or the surface is located inside a hole), as well as if the polygonal object does not contain a closed surface of the desired type, but only a portion of it.

6.Determine whether outliers (triangle vertices whose deviations exceed a specified threshold; see the next section) should be excluded from the approximation. To do this, use the "Exclude outliers" toggle.
By default, the switch is set to I (enabled). In this case, the vertices to be excluded from the approximation are first identified, and then the fitting is performed. This requires additional resources but improves the fitting results for surfaces with a large number of irregularities (e.g., those obtained by scanning). In addition, excluding outliers helps mitigate errors in triangle selection, for example, when triangles belonging to surface transition areas fall within the selected region.
If the source polygonal object has a sufficiently smooth surface and the fitting region is defined precisely, you can disable outlier exclusion by setting the switch to position 0 (off).

7.Specify the deviation threshold that determines which vertices will be included in the fitting and which will be discarded. To do this, enter the number N in the Multiplier (N*σ) field; this number will be used to multiply the standard deviation σ (sigma). Triangle vertices whose deviation from the surface being created is less than N*σ are included in the approximation. The remaining vertices are considered outliers.

8.Evaluate the accuracy of the approximation using the Result fields. If the deviations are too large, adjust the fitting parameters (for example, reduce the range of values considered by changing the number N).

9.Select the coordinate system relative to which the surface being created will be positioned. To do this, use the CS list in the Coordinate System section.

10.If necessary, you can create a local coordinate system without interrupting the operation. To do this, use the "Create LCS" button located next to the coordinate system selection list. Clicking the button launches the LCS creation subprocess. Set the LCS parameters and click the Create Object button. The system will return to the surface fitting process. The new LCS will be added to the list of coordinate systems and will be automatically selected.

11.If necessary, use the controls in the Properties section of the Parameters panel to specify a name for the surface you are creating and its display properties. Control the color and optical properties of objects...

12.To complete the operation, click the Create Object button.
A surface with no history will appear in the model, inscribed within the selected area of the polygonal object’s surface. Both the created surface and the original polygonal object are displayed in the graphics area. The Design Tree displays the surface’s name and its icon .

13.To finish the task, click the Finish button.