CMSC 110 (Introduction to Computing)

Fall 2012

Assignment#4

Due before start of class on Wednesday, October 24, 2012

Design an interactive art composition based on classes.  A new object should appear wherever the user clicks on the sketch, and each object should be animated with time.  For example, clicking could generate a snowflake that falls, or a set of concentric circles that expand outward in a rainbow and then collapse inward.  The objects can layer on top of each other in any order.  In this project, we will be limiting the overall number of objects that can appear in the sketch.

To get you started, write a class for your object using the following template:

```/** Your header comments go here to describe the class */ class MyObjectNameGoesHere { ```

```    // the object's x-coordinate     int x;```

```    // the object's y-coordinate     int y;```

```     /** Constructor      * @param xCoordinate the initial x coordinate of the object      * @param yCoordinate the initial y coordinate of the object      */     MyObjectNameGoesHere (int xCoordinate, int yCoordinate) {         ...     } ```

```     /** Draw the object.       *   This function should be called every iteration of draw() to display the object.      */     void display() { ```

```        // drawing code for your object, with an animation based on t         ...        ```

```    } ```

```    /** Advance the object's animation.       *   This function should be called every iteration of draw() to advance it's animation.      */     void step() {```

```        // increment the animation          ...        ```

`    }`

`}`

You do not need to follow this template for your class exactly, it is merely a suggestion.  You must also create the controlling code that creates new objects based on where the user clicks and drawing code that displays all of the animated objects.  Again, here is a template to get you started:

```// The maximum number of objects that can be displayed at once (your sketch must work if this value is changed!) int MAX_NUM_OBJECTS = 20; ```

```// An array of all the created objects MyObjectNameGoesHere[] myObjects = new MyObjectNameGoesHere[MAX_NUM_OBJECTS]; ```

```// An index into the myObjects array to show where to save the next new object.  Note that // this index cannot ever be allowed to exceed MAX_NUM_OBJECTS; instead it should // cycle from 0 to MAX_NUM_OBJECTS and then be reset to begin again at 0. int idxMyObjects = 0; ```

```/** Processing's setup function */ void setup() {```

```    size(500,500);     ...```

```} ```

```/** The main drawing loop for Processing */ void draw() {```

```    background(255);  // NOTE:  you are welcome to change this background ```

```    // use a for loop to display all of the objects and advance their animations     // NOTE:  When writing this loop, you will need to test each element of the myObjects array to see if it is a object or is empty.      //            Use the following code as we discussed in class:   if (myObjects[i] != null) { ... }    This example uses i as the loop variable;     //            your implementation may use something different.```

```    ... ```

```} ```

```void mousePressed() {     // create a new object based on the location clicked and store it into myObjects[idxMyObjects]     ... ```

```    // increment the index into myObjects, keeping it in the range 0...MAX_NUM_OBJECTS     // NOTE:  Make sure you understand how this line of code works!  It is complete as-is.      //        You don't need to do anything else to make the idxMyObjects counter work correctly.     idxMyObjects = (idxMyObjects+1) % MAX_NUM_OBJECTS;```

`}`

Be sure to note that you must fill in code wherever you see an ellipsis (...) at a minimum, but you will most likely need to add other variables and functions as well.  Be creative and artistic!!  For example, add a background that moves behind the objects.

Hints:

• Keep it simple at first.  Start with something basic, get it working, and then build upon it piece by piece, each time ensuring it is working before you move on to the next piece.
• Start with a hand-drawing of what you want, preferably on graph paper.
• START EARLY!!!  I cannot emphasize this enough.

Submission Instructions (including what to submit) are available here.