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Computer Science
COMP 1005
Jason Hinek

The draw function. • Unusual function which introduces a time element into the code. • Called automatically from after setup() and is like an infinite loop. It executes the code inside the function perpetually. You never call the draw function explicitely. • Can be stopped by stopping the program or calling the noLoop() function from within the function. • The number of times n the draw() function executes in each second may be controlled with the frameRate() function. • The default frame rate is 60 frames per second but you can e.g. make it say 30 frames per second as follows: frameRate(30) If you can’t call the draw functions how do you pass parameters to it? You use global parameters. Example: A moving circle in one dimension. //MOVING CIRCLE in ONE DIMENSION // Make these variables Global int x= 20; int y =250; int radius=20; void setup(){ size(500,500); framerate (60); } // THE DRAW FUNCTION void draw(){ drawcircle( ); } void drawcircle(){ background(0); // set background to zero…wipes out previous circle // to give the illusion of motion ellipse(x, y, radius, radius); //when circle gets to the right hand side reset it to the left hand side if(x>480){ x=20;} else {x=x+1;} } Example 2 //MOVING CIRCLE in TWO DIMENSIONS // Global Variables int x= 20; int y =250; int vx=3; int vy = 6; int radius=20; // setup Function void setup(){ size(500,500); // note that default framerate = 60 frameRate(120); } void draw(){ drawcircle( ); } void drawcircle(){ background(0); ellipse(x, y, radius, radius); if ((x<0)||(x>500)){vx = -vx;} if ((y<0)|| (y>500)){vy = -vy;} x=x+vx; y=y+vy; } Example 3 // Moving Circles in two dimensions using Angles // Here we do not think in terms of speed but the angle of motion //Global variable declaration float x= 0; float y =500; float radius=10; float angle = -3.14159/6.0; void setup(){ size(500,500); drawcircle( ); } void draw(){ drawcircle( ); } void drawcircle(){ background(0); ellipse(x, y, radius, radius); if((x>500) ||(x<0)||(y>500) ||(y<0) ){ angle = 3.14159 - angle ; x=x+1*cos(angle); y=y+1*sin(angle);} else {x=x+1*cos(angle); y=y+1*sin(angle);} } Using the Mouse An example of event driven code. The program is driven b
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