Example 2.5.1: The module RunPythonScript

     This example is also available on YouTube.

Introduction

The module RunPythonScript allows to execute Python scripts from within a MeVisLab network. You can draw parameter connection from modules to RunPythonScript and back, to process parameter fields using Python scripting.

Steps to do

Develop your network

In this example, we like to dynamically change the color of a cube in an Open Inventor scene. For that, add and connect the following modules as shown.

Scripting using the moduule RunPythonScript

Open the panel of RunPythonScript. There is an option to display input and output fields. For that, tick the box Fields on the top left side of the panel.

You can also name these fields individually, by ticking the box Edit field titles. Call the first input field TimeCounter and draw a parameter connection from the field Value of the panel of TimeCounter to the input field TimeCounter of the module RunPythonScript. We can name the first output field DiffuseColor and draw a parameter connection from this field to the field Diffuse Color in the panel of the module SoMaterial.

The module TimeCounter counts in a defined Frequency. We like to randomly change the color of the cube in the frequency the TimeCounter counts. Add this code:

import random

red = TimeCounter * random.randrange(0,52)/255
green = TimeCounter * random.randrange(0,52)/255
blue = TimeCounter * random.randrange(0,52)/255

updateOutputValue("DiffuseColor", str(red) + " " + str(green) + " " + str(blue))

To update the output field DiffuseColor, it is important to use the methods updateOutputValue(name, value) or setOutputValue(name, value) instead of simply assigning a value to the output field.

You can now see a color change in the viewer SoExaminerViewer every time the TimeCounter counts.

Summary

• The module RunPythonScript can be used to process module fields in your network using Python scripting.
• Use the methods updateOutputValue(name, value) or setOutputValue(name, value) to update output fields of RunPythonScript.