Recall that creating or declaring a variable can be done as follows:

Transcription

1 Lesson 2: & Conditionals Recall that creating or declaring a variable can be done as follows:! float radius = 20;! int counter = 5;! string name = Mr. Nickel ;! boolean ispressed = true;! char grade = A ;! long distance = ;! double calibration = ; Each variable has been created and assigned an appropriate value. (Note: If you try assigning a value of the wrong type it would result in a syntax error) Random Values Sometimes we want values to be unpredictable! To get a random value between 0 and 255:!! float red = random(0,255);! float green = random(0,255);! float blue = random(0,255); Take a look at the example given in the Learning Processing text about a robot called Zoog. Zoog has position variables zoogx and zoogy. The position of each of Zoog s shapes are relative to these variables (all shapes are drawn a distance away from zoogx and zoogy). Notice in the code what happens to Zoog s eyes! float zoogx; float zoogy; float eyer; float eyeg; float eyeb; void setup() {! size(200,200);! zoogx = width/2;! // Zoog always starts in the middle! zoogy = height + 100;! // Zoog starts below the screen! smooth(); }

2 void draw() {! background(255);! // Set ellipses and rects to CENTER mode! ellipsemode(center);! rectmode(center);! // Draw Zoog's body! stroke(0);! fill(150);! rect(zoogx,zoogy,20,100);! // Draw Zoog's head! stroke(0);! fill(255);! ellipse(zoogx,zoogy - 30,60,60);! // Draw Zoog's eyes! eyer = random(255);! eyeg = random(255);! eyeb = random(255);! fill(eyer,eyeg,eyeb);! ellipse(zoogx - 19, zoogy - 30, 16, 32);! ellipse(zoogx + 19, zoogy - 30, 16, 32);! // Draw Zoog's legs! stroke(150);! line(zoogx - 10, zoogy + 50, zoogx - 10, height);! line(zoogx + 10, zoogy + 50, zoogx + 10, height);! // Zoog moves up! zoogy = zoogy -1; } Copy this code into Processing and try it! Action 1. Change your snowman/robot code to move based on two variables much like Zoog.! Save your work into your M Drive as Robot or Snowman.! Submit your work by copying it into your folder in the Hand-In folder (I Drive)

3 2. Create a program that draws randomly sized, positioned and coloured balloons (Alpha should be set to 50). Save your file as Balloons and submit.! Bonus: Add a string to the balloon whose length is twice the diameter. Change the thickness of the string accordingly!

4 Conditions We ve already seen decisions being made in example programs: void setup() {!! size(480, 120);!! smooth();!! if (mousepressed == true) {!!! fill(0);!!! else {!!! fill(255);!!! ellipse(mousex, mousey, 80, 80); Try it! The colour of the ellipse is based on whether or not the mouse is pressed. How fun! Numbers and variables can be compared in a similar way, making our programs instantly very powerful and dynamic.! int rad = 15;! // Width of the shape! float xpos = 200;! // Starting position of shape! float speed = 4;!! // Speed of the shape! int xdirection = 1;! // -1 for Left and +1 for Right! void setup() {!! size(400, 200);!! smooth();!! background(100);!! xpos = xpos + speed * xdirection ; //move the ball!! if (xpos > width) { // check if the ball s x pos!!!!!! // is greater than the right!!!!!! // of the screen!! xdirection *= -1;! //change the direction!!!!! ellipse(xpos, 75, rad, rad);

5 Try it! Numbers can be compared using the following relational operators Action Modify the program so the ball bounces off the left wall by adding an if statement below the existing!...!! background(100);!! xpos = xpos + speed * xdirection ; //move the ball!! if (xpos > width) { // check if the ball s x pos!!!!!! // is greater than the right!!!!!! // of the screen!!!xdirection *= -1;! //change the direction!!!!!!! if (xpos?????????? ) {!!! xdirection *= -1;!!! ellipse(xpos, 75, rad, rad);