Meshing with Blender

Blender is a 3D tool that is primarily developed for arts. Nevertheless it is usable for editing meshes for engineering purposes as well. In this post I will give some tips and tricks for meshing with Blender. It is assumed that you already have followed a basic tutorial on Blender, for example the ones found here: https://www.blender.org/support/tutorials/

Note: Blender can be used to clean-up and repair meshes, it can not be used to make smooth panel distributions for diffraction analysis.

Numbers

Engineers like numbers. In Blender it is possible to inspect and modify the coordinates of one or more points (vertices).

The location of a vertex in blender has TWO parts.

The position of the vertex in the object (the local transform)
The position of the object in the model (the global transform)

The global transform may include rotation and scaling. So for checking numbers it can make sense to merge the two transforms into one. This can be done as follows:

In object mode: Select the object
Press Ctrl + A
Select Apply -> All transforms

To check or edit the coordinates of a vertex

Select the object
Go to Edit mode, either by pressing tab or by using the drop-down menu on the top-left
Enable vertex selection mode, either by clicking the icon with the . (dot) or by pressing 1
Select one of more vertices. Their local or global position is now shown in transform tab. For multiple vertices the median value is shown.

Note:

Display face orientation / normals

To display the face orientation or normals in a mesh:

Go to Edit mode, either by pressing tab or by using the drop-down menu on the top-left
Click on the small arrow next to the overlay button to bring up the viewport overlays menu.
Now select Face Orientation or Normals

Simplification and cleaning up

For buoyancy meshes in DAVE the size of the panels is not important. It is only important that the panels describe the geometry well. It therefore makes sense to merge subsequent panels if their relative angle is zero or close to zero.

For purposes other than buoyancy meshes it is still a good idea to clean up the mesh before starting to refine it.

Merge faces by relative angle can be done easiest using a Decimate modifier in combination with the Planar option:

Before decimate modifier (left) and after (right)

Removal of double vertices

Duplicate vertices can be removed by merging vertices (points) based on their relative distance. This can be done as follows:

Go to edit mode (Tab)
Select all (a)
Vertex -> Merge Vertices -> By distance
Press F9 to bring up the settings menu and adapt the distance if needed.

Works on selected vertices. Press a to select all

Geometry cleanup

And then there is the mesh->cleanup menu which can be activate when in edit mode. By default the actions in this menu work on the selected geometry, so press A to select all before performing the actions.

https://docs.blender.org/manual/en/latest/modeling/meshes/editing/cleanup.html

Fill holes