Invalid Facet Repairs
Time to read: ~2 min
Generally, it is not possible to automatically correct Faces that are incorrectly defined: If they have no area (defined by points that lie on a single line), then the
'correction' is ambiguous. Similarly, if Faces exist where more than two faces meet in a single edge.
Aside from there not being a perfect solution, there are a few different ways in which the problems can be addressed:
Option: Split and Move
By turning on the Split and Move option, the tool searches for edges that are considered non-manifold (meaning there are three or more facets that use the same edge) and attempts to
determine which of the facets is most different in its orientation from the others (or which two have the smallest change in their normals relative to each other if there
are more than three). Once this has been determined, the tool separates the issue surface by moving it away by a small distance from the others and forms a new edge.
Though this approach essentially only separates problematic surfaces, this can often be enough to then manually delete surface groups that are incorrectly attached.
Note: if this option is turned off and the tool executed, it will delete problematic surfaces rather than to attempt to move them away.
Option: Project Split
This scenario is more common with some source files in that some applications are 'lazy' and rather than to generate well defined triangles, they use triangles that
have all corners on a single line as a way to bridge the region where two triangles meet partially along the edge of another. Similarly, this scenario can also occur
when an OpenGL Tessellator is used as this tool is more concerned with creating triangles for display purposes than for correct representation.
With the option turned on for project split, the application looks for edges that are on the boundary (Open Edges) and that have a vertex of another open edge in close proximity to it
(the vertex needs to be within 1/2 the edge length to be considered close). If it can find such a vertex, it splits the original facet using this location and creates new facets to
heal the resulting opening.
It should be noted that if this option is turned off and the tool is run, it will instead delete the problematic items where it finds them.
Option: All, Selected, Preview, Clear & Apply
Removal of invalids can leave the data in a problematic state and therefore it is recommended to always use the Preview option as its data is
stored in memory and, if the result is statisfactory, applying is simply swapping the current data with that already obtained.
Choice of whether to use the tool on a selected-bodies or all-bodies basis depends on whether there are multiplie bodies and how the process
is best applied.