saad-gh/irregular-surface-contact

Blender script to identify contact nodes between irregular surfaces

Overview

Blender is a power powerful 3D objects editor which provides a very easy to use interface for refining 3D models. It has a very comprehensive and well documented API which can be used for enhancing its features programatically. This work demonstrates how to utilize its API to find contact nodes between two irregular surfaces. This work was carried out after built in mesh assembly features of Salome Meca and Code Aster raised singularity errors. It was deduced that it is because of non coincident irregular surface nodes. This problem was resolved by generating contact groups on the irregular surfaces in Blender which was used to directed Code Aster to form contact exactly where it needs.

Prerequisites

Basic knowledge of Blender menus and selection

Quick Start

Requirement

Blender's python would need pandas library which can be installed in the following way

• Open 'Python Console' which is part of 'Editor Type' menu
• Execute the following to get Blender's python path

>>> import sys
>>> sys.exec_prefix
'/path/to/blender/python'

• Next from the terminal

cd /path/to/blender/python/bin
./python -m ensurepip
./python -m pip install pandas

• Restart Blender

Running the Script

• Import sample STL files (L5, disk)
• Select both imported objects from the 'Outliner' in the 'Editor Type' menu
• Open 'Text Editor' in the 'Editor Type' menu
• From the 'Text Editor' menu click 'Text > Create Text Block'
• Copy paste the code from 'appendixA2.py'
• While keeping the mouse pointer inside 'Text Editor' press 'Ctrl + p'

Contact vertex groups will be generated. Vertex groups can be viewed in 'Data' type property of 'Properties' type editor in 'Editor Type' menu

Basic Algorithm Detail

The samplesize Parameter

This parameter in the only directive set by the user which the script needs to identify contact between two irregular surfaces

• It is the number of least distant nodes between the two surfaces
• The distance of the most distant node among these nodes is the threshold
• All nodes with distances less than threshold are qualified as contact nodes

Reference

Blender: Using 3rd party Python modules

Euclidean distance

Minimum Euclidean Distance

irregular-surface-contact's Issues

gmsh

While using gmsh for creating contact groups it's required to generate the geometry from the STL model with the function gmsh.model.mesh.classifySurfaces(0) which is time consuming.

To resolve that this classification of surface should be divided on separate compute nodes. This would make grouping convenient since gmsh preserves the groups in a way that they are readily available in Code Aster solver. Generating contact groups with Blender requires some manual work to preserve groups which is error prone.