Invalid Geometry

When importing geometry into Slide2, you are guided through a validation step. The geometry validation tool identifies 5 categories of possible problems:

1. Near-degeneracies: Triangles with a high aspect ratio and vertices, edges, or triangles that are close to each other
2. Near-folding: Non-smooth features that look like they are nearly self-intersecting
3. Non-manifold features: A surface is manifold if it is continuous and non-self-intersecting
4. Holes: There should be no holes on the surface of an entity
5. Self-intersections: When triangles intersect, or nearly intersect, in their interiors. Clean triangles should only touch on their vertices or edges

The following free software, among others, can help you clean your geometry before importing it into Slide2:

• Meshlab: http://www.meshlab.net/
  • Meshlab has a large collection of "Filters" which indicate different ways to identify or fix a specific problem
• Ramesh Cleaner: https://www.scaninabox.com/2017-09-14-12-09-23/downloads/software-utilities-and-documents.html
  • This is a simple tool that can quickly identify and fix local geometry problems
• OpenFlipper: http://www.openflipper.org/
  • You can use OpenFlipper to identify non-manifold features and poor-quality triangles. It also has hole-filling, small feature collapsing, and global re-meshing tools
• Blender: http://www.blender.org/
  • Blender allows low-level editing of vertices, edges, and faces. It can identify non-manifold features and can collapse small features both globally and locally.

Our validation tool allows you to group features into visible clusters:

• If the clusters end up spanning the entire piece of geometry, you will likely need to globally re-mesh the model (approximating the original geometry with a new set of triangles). Meshlab and OpenFlipper each have a set of re-meshing tools. For example, the image below depicts OpenFlipper's Adaptive Remesher:

• If you see only a few isolated clusters of problems, then you can use local cleaning tools. Often the simplest way to overcome these issues is to delete the area, then fill the resulting hole. Ramesh Cleaner is the simplest among the listed software, so we recommend starting here. All software listed above has tools for local cleanup and hole-filling.
• If your geometry defines excavations or other artificial structures, and you need to preserve as much shape and detail as possible, you may need to manually edit the vertices or triangles in the geometry. Blender supports this type of low-level editing.