# Fiber Angle Fit

### Description

• These step-by-step instructions will guide you through fitting fibers’ orientation data in 2D space (on a plane)
• Fiber is an important structure of cardiac muscle which plays a critical role in cardiac muscle properties.
Therefore, the heart model will be realistic if it has fiber data.

• The concept of fiber fitting is to put the initial value of fiber angle (in radian) which should specifically refer from Xi(1) or Xi(2) direction
• An automated script that runs this tutorial is included in the Continuity installation: \examples\data02\cubic_fib_fitting.py. To run it, click File→Read script→Python or session script

### Start Continuity

• Launch the Continuity Client
• check the fitting box under Use Modules:

• Click OK to bring up the main window

### Set up mesh

• Select rectangular cartesian in the Global Coordinates: pop-up menu

• Click OK to submit Coordinate Form

• Choose Lagrange Basis Function→2D→Linear-Linear

• Choose Hermite Basis Function→2D→Cubic-Cubic

• Verify that the list of basis functions now contains:
• Linear-Linear Lagrange 3*3
• Cubic-Cubic Hermite 3*3
• Click OK to submit Basis Form

• Click Import/Export/Graph button to open Continuity Table Manager

• Select tab-delimited nodes file ( nodes.xls )

• You should now have nodes numbered 1-25
• Click on the Field Vector 1 tab

• Select Cubic-Cubic under Field Variable 1

• Click on the Fiber Angle tab

• Select Cubic-Cubic under Fiber Angle, Transverse Angle, and Sheet Angle

• Click OK to submit Node Form

• Click Import/Export button to open Continuity Table Manager

• Select tab-delimited elements file ( elems.xls )

• You should have 16 elements in the list
• Click OK to submit Element Form

• Click the lines radio button

• Click Render

• Click on the OK Button

• Leave default settings and click OK

• The mesh should now look similar to the first screenshot above

### Set up fitting

• Select fitting and click OK

• The menu bar should now show the Fitting command
• Click Import/Export/Graph button to open Continuity Table Manager

• Select tab-delimited data file ( data.xls )

• You should now have Data numbered 11-169
• Click OK to submit Data Form

• Simply click OK after opening the Weights form

• Simply click OK after opening the Constraints form

• In the Cooridinates tab, select coord_1, coord_2, coord_3 for the three coordinates

• In the Fibers tab, select field1_Var1 for Fiber Angle

• In the Fitting Variables tab, *deselect* Coordinate 1, Coordinate 2, Coordinate 3, and Fiber Angle

• Click the Fit button (Don’t close the Fit Data form yet)

• Go back to the Fit Data form. In the Fitting Variables tab, check only the Fiber Angle checkbox

• Click the Fit button

• Mesh→Render→Fibers… (Note: you should render mesh fibers, not fitting fibers)

• Leave the default values and click OK

• Click on fiber vectors4 in the list on the left

• Click on the Colors tab

• Change the R,G,B color field to 1,0,0 to change the color to the brightest red

• Click on data vectors3 in the list on the left

• Change the R,G,B color field to 0,1,0 to change the color to the brightest green

• Click somewhere in the rendered window to refresh the image
• The mesh should now look similar to the second screenshot above

### Pre-built model

This cont6 file contains all data and parameters for this problem: fit3.cont6