1         Learning Environments for Graphics
LEG01 Transformation Matrices

1.1        Copying and starting the Java LEG environment


Student preparation:




Copy over the “LEG01_ver_1_1.ZIP” file from web site, and run this Java application from the DOS prompt:

·        Download the “LEG01_ver_1_1.zip”  from the downloads section of the web site:

·        Create a folder (for example C:\LEG01\) and extract all files from the LEG01_ver_1_1.ZIP file into your new folder

·        Open a DOS window

o       START | RUN | command <enter>

·        Change to the folder you have copied

o       E.g. in the DOS window C:\> type:                   cd \leg01

·        Run the program

o       In the DOS window C:\LEG01> type: java LEG01
(this runs the Java interpreter for this project)

·        The LEG01 application window should appear


You learn:

·        To download a ZIPed file from the COM 2300 web site

·        To run a compiled Java program from a DOS window

·        how to start the “LEG01” learning environment


The LEG01[1] environment has been developed to support your learning, feel free to take a copy home on disk / ZIP and run from home (you’ll need the JDK 1.3 installed).

This LEG01 environment has been written in Java – all the source code is available (see the “.java” files). Feel free to examine / change these files for your own use.

1.2        Getting to know the LEG environment


Student preparation

Complete the previous exercise to get the LEG environment running



Clicking the mouse cursor into one of the matrix text boxes allows you to repeat a transformation by pressing the <RETURN> key.


Try to achieve the following (after each click UNDO ALL TRANSFOMATIONS):

·        Translate (move) the house so its centre is over the origin


·        rotate the house by a quarter turn about (0,0) anti-clockwise


·        scale the Y values of the house (by a factor of 2) but do not change the X values


·        rotate the house by 5 degrees anticlockwise and make the house circle the origin by clicking the [] LOOP check box


·        make the house “lift off” by:

o       translating it to the origin

o       rotating it so it points to the top right

o       translating it (with LOOP) so it goes in a straight line off the top left of the screen


·        make the house rotate about the origin while the roof points towards the origin:

o       translating so the roof points to the origin

o       rotating it  (with LOOP)


·        enter the following matrix (to reflect about the line Y = -X) and click the LOOP button – the house should jump back and forth


·        enter the following matrix (to scale by 80% both X and Y) – and press the <RETURN> key a few times to reduce the size of the house


·        enter the following matrix (to rotate by 10 degrees anticlockwise) – and press the <RETURN> key a few times to make the house rotate around the origin




You learn:

·        how to instruct the LEG environment to perform transformations

·        how you can see the relationship between a 3x3 matrix and a 3D transformation

·        how to enter a matrix and see the transformation take place


[1] Learning Environment for Graphics : LEG