Design & Analysis of Hermite Surfaces

Bicubic Hermite Surface is an extension of Hermite Curve. The Hermite Surface is defined by 16 parameters (4 end points, 8 tangent vectors at end points, 4 twist vectors). It is challenging for students to understand the changes in surface as the change in parameters. This is a GUI which simulates the behavior of this surface is created within NX using NX API, C++ and Ufuncs. This enables students to interact with GUI by providing various surface parameters and visualize their effect on the shape of surface. This tool assists students with their assignment in visualizing and validating their work.

Installation Manual

  1. Download and extract the contents of the .zip file named Design & Analysis of Hermite
  2. Open the extracted folder named Design & Analysis of Hermite Surfaces.
  3. Open the folder named ug_customization. Right click on the Windows Batch File named nx and open with Notepad/Notepad++.
  4. Find the current file path of the nx file in your computer (Right click >> Properties). Copy the file path and paste it in the first line (the highlighted portion in the notepad as shown below).
  5. Change the version of Siemens NX to the one you are using (module works for Siemens NX 10.0, 11.0, and 12.0) in the third line of the notepad file (as highlighted below).
  6. Once these steps are carried out, you have completed the installation procedures before launching the application.
Support Accessibility Output Window
Support Accessibility Output Window

Instruction Manual

  1. Now, double-click nx to launch the Windows Batch File. This will launch the Siemens NX window and a terminal window (you can minimize it or close it – it contains the information you input in steps 4 and 5). You may notice the UC Geometric Modeling Modules tab in the top toolbar. Click on it. The Design & Analysis of Hermite Surfaces module will be visible.
  2. To create a hermite surface the user is supposed to specify all the 16 parameters. For illustration purposes, the text files with hermite surface parameters are saved in the folder named Examples.
  3. Once the Siemens NX is launched, you can click on the Design & Analysis of Hermite Surfaces button on the Command Ribbon. 
  4. The Design & Analysis of Hermite Surfaces GUI is shown in the figure below. The detailed explanation of each option in the GUI is given below.
NX API based GUI

a) Position vectors
The four corner points of the surface.

b) Tangent vectors
The tangent vectors in u, w directions at all the four position vectors of the surface.

c) Twist vectors
The twist vectors at all the four position vectors of the surface.

d) File Browser
Browse the text file with the parameters of the hermite surface to be generated.

e) Read
Used only when getting the surface parameters from a file. Reads the parameters of the hermite surface (position vectors, tangent vectors and twist vectors) in to the GUI.  

f) Update
Generates or updates the hermite surface according to the parameters specified manually or read using the appropriate text file.

g) Unit normal
Generates the unit normal for the hermite surface at the given U, W.

h) Tangents
Plots all the tangent vectors for the hermite surface.

i) Clear tangents
Clears tangents plotted on all the hermite surfaces.

j) Normals all over the surface
Generates normals all over the surface to visualize the change in shape of the surface in the U, W space.

k) Clear normals
Clears all the normals generated on the surface.

l) Clear all
Clears all the plotted surfaces, tangents and normals.

If the changes made are to be saved use ‘OK’ or ‘Apply’, else use ‘cancel’.

Plot of Multiple hermite surfaces by varying surface parameters

5. The output window of the Design & Analysis of Hermite Surfaces module is shown below. The result consists of the hermite surface, tangent vectors, normal at the specified U, W.

Plot of Hermite surface with normals all over the surface

Please watch the video tutorial of the module for an example included with the zip file of the module.

Example Problem

Try out the following to learn the impact of change in parameters (position vectors, tangent vectors, twist vectors) on shape of surface.

Generate and plot the hermite surface with the following parameters:

a.)   The position vectors of four corner points are:

P (0,0) = [-50 0 50], P (0,1) = [-50 -50 -50], P (1,0) = [50 -50 50], P (1,1) = [50 0 -50].

The tangent vectors are:

Pu (0,0) = [50 50 0], Pu (0,1) = [5 5 0], Pu (1,0) = [5 -5 0], Pu (1,1) = [5 -5 0],    

Pw (0,0) = [0 20 -20], Pw (0,1) = [0 -5 -5], Pw (1,0) = [0 5 -5], Pw (1,1) = [0 -5 -5].

The twist vectors are:

Puw (0,0) = [0 0 0], Puw (0,1) = [0.5 0.5 0.5], Puw (1,0) = [0.5 -0.5 -0.5], Puw (1,1) = [0 0 0].

Plot the surface and determine unit normal vector at u=0.25, w=0.75.

b.)   Multiply the tangent vectors by a scalar 5 and replot the hermite surface. Observe the impact of tangent vectors on the shape of the curve.