There are two types of mesh: Watertight and Unwatertight.
A Watertight mesh automatically fills any holes by adding triangles based on the scanned data, effectively "closing" the model. This is ideal for applications like 3D Printing or Virtual Reality.
An Unwatertight mesh, conversely, leaves the model open and does not fill holes. It connects points that are within a specified distance of each other. This type of mesh is more suited for tasks such as Reverse Engineering, Inspection, or further model editing.
This article will demonstrate the varied results achievable by using different meshing options, aiming to clarify their distinctions.
For this example, a gearbox was scanned using the EinScan Pro 2X. The scanned data comprises 1,552,721 points across three projects, totaling 3.25 GB. The image below shows the gearbox used in this demonstration.
The gearbox was scanned only on one side, which means there is no data for the bottom of the part, as the image illustrates.
After generating the Point Cloud, the scanned data can be meshed. The software provides two meshing options: Watertight Model or Unwatertight Model. Additionally, a checkbox for Data optimization is available.
Watertight mesh
For the watertight mesh, you can choose from three resolution levels: High, Medium, and Low detail.
The three resolution settings—High, Medium, and Low—determine the spacing between the vertices of the mesh's triangles. Greater detail results in smaller and more numerous triangles. Consequently, higher detail levels require more computation time for meshing. The table below illustrates these differences.
| Number of triangles | File size (MB) | Computing time (minutes) | |
High detail | 2.506.620 | 193 | 24 |
Medium detail | 2.500.074 | 185 | 15 |
Low detail | 1.615.962 | 118 | 11 |
The three images below display magnified views of the watertight meshes at different detail levels: high (top), medium (middle), and low (bottom).
Subtle differences are noticeable among the three detailed meshes. The high-detail mesh retains the roughened areas present on the gearbox surface, while the low-detail mesh appears smoother.
Similarly, the high-detail mesh has closed some holes, introducing excessive sharpness in certain areas. This makes the other meshes appear finer in those regions, particularly noticeable on the shaft in the center of the image.
Furthermore, the medium and low-detail meshes have distorted the hole on the left, whereas the high-detail mesh accurately preserves its cylindrical shape.
Users must select the mesh that best aligns with their project requirements and desired outcome. This often involves balancing various features to find an optimal compromise.
*NOTE: As previously stated, the watertight mesh automatically fills in any gaps using the scanned data. Notice how the software completed the bottom of the part, even though it wasn't scanned.
The outcome can be unexpected as the software, lacking complete information, disregards the part's true shape. It uses only the available edge data, specifically the points and curvature, to generate polygons and close the mesh.
Unwatertight mesh
The outcome can be unexpected as the software, lacking complete information, disregards the part's true shape. It uses only the available edge data, specifically the points and curvature, to generate polygons and close the mesh.
The unwatertight mesh details are illustrated below.
Number of triangles | File Size (MB) | Computing time (minutes) | |
| Unwatertight mesh | 2.461.494 | 200 | 20 |
The result is a hollow mesh made up solely of the data captured by the scanner.
Conclusion
If a solid mesh is needed from the scanned data, users can select the Watertight option and choose from three detail levels based on their project requirements. On the other hand, if you only need the scanned surface for further processing or additional tasks, the Unwatertight option is recommended.