UPDATES:

• Comments have been added to LuxoApplet.java.

Ground Rules:

• Feel free to discuss assignments and your approach with others.
• The design and code must be your own.
• Don't use code from previous semesters.
• Cite any models, images, ideas, or algorithms that you do not develop yourself
• Assignment is due before midnight of the day indicated
• A working version of your applet and source code must be linked to your course home page.  
• You must test to make sure your applet is runnable by following links from the students link off the course webpage.
• All source code must also be submitted via Athena's turnin procedure
• Check this page frequently for updates and clarifications

In this assignment you will write code to move two 3D articulated figures (Luxo lamps) and navigate three virtual cameras. These interactions are with respect to various coordinate frames associated with the different Luxo lamp elements and cameras. You are supplied with a Java class files that implement a 4 by 4 Matrix Stack as well as a 3D rendering system. These classes are stored in a single archive file called Project3.jar. In order, to make use of this file you must either include it in your CLASSPATH or unzip the archive's contents into you working directory. No source code is provided for these classes.

All of your code modifications must be confined to a single file called LuxoApplet.java. This file contains two classes. The class LuxoApplet has sets up the panels and buttons used in the user interface. It is unlikely that you will need to change any code in this class, other than possibly renaming the user-defined buttons to provide optional capabilities. The majority of your code changes will to the LuxoCanvas Class.

To begin with, you are given an operational, but incomplete, version of the LuxoCanvas Class. You goal in this exercise will be to implement each Button and Mouse function as specified. You are free to change any or all of the LuxoCanvas Class. This includes adding, deleting, or redefining methods in the supplied class.

As provided, the LuxoApplet code operates as follows:




The scene is composed of four elements. The top of the tan ground plane is the plane z = 0. The global origin is at the center of this plane. You will find three characters are placed on the plane. These are: a blue mom Luxo lamp, a second smaller red Luxo lamp (who we will call Jr.), and a ball with a star on top.

Dragging the mouse inside the viewer canvas, with the left-button pressed, causes the viewpoint to orbit the scene. Pressing the right-mouse button generates a short animation while timing the renderer. If you find the rendering speed too slow (less than 300 mS per frame) you should consider shrinking the size of the applet. As small as 300 by 300 should still be usable. Note: On my relatively slow 266 MHz Pentium II, I get around 100 mS per frame in IE 5.0 when the applet is set to 400 by 400. Of the 16 buttons provided, only the Reset button does anything. The other buttons merely print their function number on the applet's status line.

Each of the Luxo lamps has only 4 degrees of freedom, each represented by a joint angle. You are not permitted to add any new degrees of freedom, beyond those expressed in the DrawMom( ) and DrawJr( ) methods. You may, however, rewrite these methods in any other fashion you deem necessary. The 4 movable joints, along with their relative coordinate systems, are shown in the following diagram:



Note that the y axis (green) for all frames extends out of the plane of the page.

• The Reset button should force the LuxoCanvas into the "sky camera" mode, set the viewpoint to [0, -60, 24]^T, and look at the global origin with the global frame's z-axis pointing up. You should also place the Luxo lamps into a known configuration. The mouse functions will then operate in sky camera mode as described below.
• The Sky Cam will set the view to the position and orientation to the "sky camera". In sky camera mode the mouse should exhibit the following behaviors. With the right button down, moving the mouse right causes the sky camera to translate right (the x direction of the sky camera's frame), moving to the left translates left, moving up translates up (the y direction of the sky camera's frame), and moving the mouse down translates down. When the left button is pressed, moving the mouse right causes a rotation about the camera's y-axis by a negative angle, moving the mouse left causes a positive rotation, moving up causes a positive rotation about the x-axis, and moving the mouse down causes a negative rotation about the camera's x-axis.
• Both the Mom Cam and Jr Cam use the same mouse interface. The viewpoint is determined by the position of the cyclopean eye, and looks in the -z direction of the lamps head. Mouse motions to the right and left will cause a corresponding rotations about the z-axis of the lamp's base, on either button press. Mouse motions up and down will rotate the head of the lamp correspondingly when the left button is pressed. When the right mouse button is pushed the lamp should rotate about its elbow joint (between its body and neck section) in a direction that consistent with the mouse's motion. Mom Cam and Jr Cam rotations actually change the lamp's pose as well as the camera's position and orientation. The mouse behavior is completely determined the current camera mode. No other buttons do effect the interpretation of mouse presses and movements.
• The Mom @ Jr button should cause the Mom Lamp to look at the Jr Lamp. This will cause rotations about the z-axis of the Mom lamp's base, and the y-axis of the Mom lamp's head such that Mom's eye "looks" at Jr's Eye along the -z direction of the mom lamp's coordinate frame. It is okay if Jr's eye is covered by its shade, but mom should have an unimpeded view of Jr.
• The Mom @ Ball button causes the Mom lamp to look at the center of the star on the ball, by rotating about only the mom lamp's base and head joint.
• The Jr @ Mom button should cause the Jr Lamp to look at his mom. This will cause rotations about the z-axis of the Jr lamp's base, and the y-axis of the Jr lamp's head such that Jr's eye "looks" at Mom's Eye. It is okay if mom cannot see Jr's glance, but Jr should have a clear view of mom.
• The Jr @ Ball button causes Jr to look at the center of the star on the ball, by rotating about only the lamp's base and head joint.
• The Move Jr N button should translate the Jr lamp 1.0 unit in the direction of the global frame's y-axis.
• The Move Jr S button should translate the Jr lamp 1.0 unit in the direction opposite of the global frame's y-axis.
• The Move Jr E button should translate the Jr lamp 1.0 unit in the direction of the global frame's x-axis.
• The Move Jr W button should translate the Jr lamp 1.0 unit in the direction opposite of the global frame's x-axis.

You will need to make extensive use of the MatrixStack class in this assignment. MatrixStack provides the following access methods.

public class MatrixStack extends Matrix4x4 {
  public MatrixStack();                      // matrix stack with default depth
  public MatrixStack(int depth);             // matrix stack with specific depth
  public MatrixStack(Raster r);              // Initialize with viewport mapping (default depth)
  public MatrixStack(Matrix4x4 copy);        // Initialize with matrix (default depth)
  public void push();                        // Push copy of current tos
  public void pop();                         // Pop matirx to current tos
  public void set(int j, int i, float val);  // set element of current matrix[4][4]
  public void set(int i, float val);         // set element i of current matrix[16]
  public float get(int j, int i);            // get element of current matrix[4][4]
  public float get(int i);                   // get element of current matrix[16]
  public void copy(Matrix4x4 src);           // copy matrix to current matrix
  
  // Transform one list of 3D vertices to another using the matrix
  // on the top of the stack. The in and out arrays can be the same.
  public void transform(Vertex3D in[], Vertex3D out[], int vertices);
  
  public Vertex3D transform(Vertex3D in);     // transform a single vertex using the
                                              // matrix on the top of the stack

  public final void compose(Matrix4x4 M);     // compose the matrix M with the matrix
                                              // on the top of the stack:
											  //   M[tos] <- M[tos]*M
  public void loadIdentity();                 // load the current matrix with identity 
  public void mult(float r[]);                // compose the tos with the 16 element array
  
  public void translate(float tx, float ty, float tz);	// compose the tos with a translation
  public void scale(float sx, float sy, float sz);      // compose the tos with a scale
  public void rotate(float ax, float ay, float az, float angle);  // compose the tos with a rotation
  public void lookAt(float eyex, float eyey, float eyez,          // compose the tos with a viewing matrix
                     float atx,  float aty,  float atz,
                     float upx,  float upy,  float upz);
  
  public void frustum(float left, float right,  // compose the tos with a prespective
                      float bottom, float top,  // projection matrix
                      float near, float far);
					  
  public String toString();
}

You can use the 4 user-defined buttons to add your own functionality. Some potential ideas are given below.
• Add more interesting positioning commands. For instance, Jr on Ball.
• Deflate Ball Consider preserving the surface area as you deflate it.
• Limit joint angles to avoid self-intersections
• Add the capability to zoom in and out within the current camera's view.
• Make each button click cause a multi-frame animation. Or add a special key for a particular animation. For example add a Jr. Dance button, or Mom Nod.
• Define a different camera interface. For example a Ball Cam.
• Add a Roll Ball button.
• Try raising the lamps head while constraining it to look at a fixed point. Perhaps by adding Raise Jr and Lower Jr buttons.

• You will need the classes contained in the archive Project3.jar to create your applet. Source code will not be provide for these classes. You can access the contents of this Jar file by adding it to your CLASSPATH environment variable. If you have no luck making this work within your development environment you may unzip the jar file and place the class files that it contains in the same directory as the code you are developing. Do not wait to the last minute to find out which approach works for you. The staff will be unsympathetic to those people who try to figure out how to link in these classes on the night of the due date.
• A template for you applet is provided in LuxoApplet.java. This is the same working version of the code that is displayed elsewhere on this page. I suggest that you try compiling this code without modification first, and try a few incremental experiments before setting out to code the final version of your project. I recommend that you concentrate most of your changes to the LuxoCanvas class contained in that file. The primary function of the LuxoApplet class is to provide a user interface.
• You will probably find this exercise more time consuming than the two previous exercises. Try to get an early start.