Semi-Automatic Repair Options

From Netfabb Wiki

Repair context menu and Actions tabsheet

Semi-automatic repair options are applied to the whole part or the whole selection of triangles, surfaces and shells. They can be found in the context menu and in the Repair menu. The most important are also available in "Actions" tabsheet (as can be seen to the right).

Close holes

There are three ways to close holes without manually inserting the missing triangles. First, after right-clicking on the edge of a hole (marked yellow, if the visualization option "Highlight Holes" is activated), you can choose the option Close Hole in the context menu. Thus, single holes can be closed. The triangles inserted to fill the hole are automatically selected.

By clicking on Close trivial holes, all holes are closed that require either one single triangle or for which only two border edges with the same corner point coordinates have to be connected.

By clicking Close all holes, all holes of the part are closed automatically. This is surely the simplest method to repair holes. However, with complicated holes regarding geometry or orientation, it may lead to unsatisfactory results.

After right-clicking on open edges, you can close single holes in the context menu.

For these holes only one triangle is missing. They can be repaired with Close Trivial Holes.

Close all holes automatically tries to repair all holes, no matter how complex they are.

Self-Intersections

Self-intersections occur whenever triangles or surfaces of one part cut through each other. netfabb is able to detect, split off and remove those self-intersections.

If you detect self-intersections, a red line will appear representing the cutting line of self-intersections. This line is also visible, when the intersections are within or at the backside of the part. If surfaces not only cut through each other, but are on top of each other, all triangles which are part of that double surfaces are marked in orange.

Split off self-intersection: The yellow line represents a border edge. The triangle mesh is adjusted on both shells.

By splitting off self-intersections, intersecting surfaces and double surfaces will be cut and divided along the cutting line, resulting in border edges along the intersections. If the surfaces are part of closed shells, sections of this shell will be cut off and can be selected and worked on separately as own shells.

The triangle mesh is changed (without changing the shape), so that neighboring border edges have identical coordinates and you get a valid triangulation across the two shells. This is done to provide easier processing when repairing the intersection (e.g. by stitching the triangles).

If you remove self-intersections, the intersections are split off, resulting interior shells and double surfaces are removed and surfaces on the outside of the part are reconnected. As a result, a valid shell is created. Self-intersections can only be removed, if the part has no holes.

Self-Intersection

Here you can see the interior of a part with removed self-intersections. Interior surfaces are removed and valid shell is created

All triangles belonging to a double surface in the interior of the part are marked orange.

Open triangle edges can be repaired with the Stitch Triangles function

Stitch Triangles

With this function, adjacent triangles are connected. Therefore, points of triangles in an identical position and the adjacent edges are merged. These edges are marked yellow, if the option "Highlight Holes" in the tabsheet is activated.

Whenever the corners of triangles are not exactly in an identical position, they are moved together. Thereby, the shape of the part is distorted very slightly. Here, the tolerance setting determines the maximum distance corners are moved.

The stitching of triangles can either be executed only with selected triangles or with all triangles. If you stitch only selected triangles, both triangles which are to be connected have to be selected.

Optionally, you can ignore the orientation of triangles. If you do so, triangles with opposing orientation will be connected as well. If you do not tick this box, the software stitches only triangle edges with fitting orientation. In general, it is recommended NOT to ignore the orientation, in order to prevent the creation of non-orientable triangle meshes.

Fix Flipped Triangles

Inverted Triangles are turned around. This is indispensable for repairing parts with an invalid orientation. In the Status tabsheet, you can see, if you have triangles with invalid orientation. The orientation of triangles can be seen easily, as the outside is blue and the inside is red (with default settings).

The inside of triangles is red so that flipped triangles can be seen easily.

In the Professional version, if the part is not orientable, a dialog is opened where you will be asked if netfabb should try to make it orientable. However, as a warning, this does not always work and may destroy the mesh. So, to be sure, it is recommended that you apply the repair before executing this function, optionally without replacing the original, and start the repair module again. Not orientable surfaces can come into being for instance because of self-intersections, or after the orientation is ignored during the stitching of triangles.

Remove double triangles

Removes triangles using the same three corner points, irrespective of their orientation. One of the triangles is kept.

Triangles with the same coordinates but different orientation

Remove degenerate faces

Degenerate faces are triangles which have no surface or only minimal surface. In the repair screen, they are marked orange. As they do not construct any surface, they usually are unnecessary. They can come into being during various operations, such as file conversion, Boolean Operations and all kinds of operations which involve retriangulations. Degenerate faces in a file principally do not result in bad parts when manufactured, but they may dramatically increase the number of corner points and hatches in the slice files necessary for the production. This may cause much longer calculation and production times.

With this function, the degenerate triangles are deleted. By setting the tolerance, you can set the maximal edge length and height of the triangles which shall be deleted.

The orange-marked triangle has no surface and consequently looks like a one-dimensional line.

Extract selected Triangles as Part

The current selection is inserted into the project as own part and is added to the parts section of the project tree. That way, for example, surfaces or single shells can be added to the project for subsequent operations. On request, you can either keep the extracted triangles in the repair or delete them.

This function can be used to start a second repair module for the extracted sections or shells only. So, you can conduct general, semi-automatic repair operations only for these extracted triangles. If you do so, delete the selection when you extracted them from the first repair and, after you have applied the second repair, use drag & drop in the project tree to move the part back into the first repair.