Blendyn Development

by Do Tien Dung, September, 2022

Project overview and objective

Blendyn is one of post-processing tools of MBDyn - multibody simulation engine. Blendyn is built as an Add-ons of Blender which allow user to visualise MBDyn output datas with 3D animations. Blendyn was first implemented in 2017. However, there are some rooms for improvement and some parts of current Blendyn was out of date. In this project, I focus on developing some of them:

1. Improving graph plotting function and adding two new plotting engines into Blendyn matplotlib and bokeh beside pygal
2. Visualising two MBDyn elements: beam slider and modal
3. Visualising internal force and internal moment for deformable elements: beam2, beam3, shell4, membrane4
4. Improving UI

Code

• Blendyn Github branch "devel2"
• File Change
• Commits History

Critical Algorithms

Animating modal

The most challenging section for visualising modal element is extract modal node data from different files and put them together in one formula to make the motion paths. The image below show how I extract and use the file data to get the modal location.

Visualising internal properties of beam2

I prefer using shader nodes to visualise internal properties of all deformable elements. The most simple one is beam2 element. beam2 have only one evaluation point in its central. Therefore, I design shader node for beam2 same as the image bellow. For each internal property value, I turn them into corresponding color in RGB shader node to set the same color for the whole beam2 object.

Visualising internal properties of beam3

beam3 element has two evaluation points in the middle of the first and second parts. They have their own internal properties values in each time point. Therefore, design beam3 shader node as bellow using Texture Coordinate and ColorRamp with linear interpolation method to show the change of internal properties along beam3 element. In addition, I use middle node object (_RF2) for source of coordinate in Texture Coordinate shader node.

Visualising internal properties of shell4 and membrane4

shell4 and membrane4 elements have upto 4 evaluation points in middle of their edges. Therefore, I have to use 2 ColorRamp shader nodes with linear interpolation. In addition, I also create one hidden empty object named elem.name + _ctr which have average location and rotation of the visualising element. The object is used as source of coordinate in Texture Coordinate shader node.

Currently, internal force and internal moment outputs for shell4 and membrane4 elements haven't implemented in MBDyn yet. I could only make some manual demo for the visualisation as the image bellow.

Example

• Beam Slider
• ssbeam
• modalbody
• Internal Force

Usage

Plotting with matplotlib

• Step1: Load MBDyn output file (.nc file)
• Step2: Select Scene Properties> MBDyn Data Plot
• Step3: Choose plotting variale (For example: node.struct.1.X)
• Step4: Choose plotting engine (Matplotlib), ploting dimension, plot frequency and plot type
• Step5: Click on Plot variable
• Step6: Open Image Editer Window and open the latest image to see the graph results

Guidance Video

Plotting with bokeh

• Step1: Load MBDyn output file (.nc file)
• Step2: Select Scene Properties > MBDyn Data Plot
• Step3: Choose plotting variale (For example: node.struct.1.X)
• Step4: Choose plotting engine (Bokeh), ploting dimension, plot frequency, plot type and output format (show in localhost or save as png)
• Step5: Click on Plot variable If you choose show in localhost, one localhost would appear on your browser with the graph
• (If you choose save as png) Step6: Open Image Editer window and open the latest image to see the graph results

Guidance Video

Visualising modal as Blendyn Components

• Step1: Load MBDyn output file (Make sure to have .mod file in the same directory)
• Step2: Standard Import
• Step3: Select Scene Properties > MBDyn Components > Add new component
• Step4: Choose elements for the component (start with "modal_")
• Step5: Choose .fem file for this modal
• Step6: Load fem file > Import all modal nodes > Add element Repeat step 4,5,6 if there is more than one modal
• Step7: Choose Mesh Object
• Step8: Confirm

Guidance Video 1

Guidance Video 2

Visualising internal force or internal moment for deformable elements

• Step1: Load MBDyn output file (.nc file)
• Step2: Tick on Import internal property
• Step3: Choose Type (internal property type), Dim (dimension), Min (Lower boundary), Max (Upper boundary)
• Step4: Standard Import
• Step5: Animate Scene
• Step6: Choose Material Preview in Viewport Shading

Guidance Video

My strace

• Blendyn development proposal
• Weekly reports

Future work

• Finishing internal force and internal moment visualisation for shell4 and membrane4 elements when their MBDyn outputs are available.
• Eventhough I have successed in visualising internal force and internal moment for beam2 and beam3, choosing correct value for Min and Max boundary is challenge. Autosetup Boundary can't solve that problem effectively. I hope that, we can have a better way to implement it in the future.
• Making 3D ploting for 'trajectory' plot type and show it in a localhost when ploting with bokeh