The Tools - Making Things Talk - page 10

Here's a second program that's
a bit more exciting. It illustrates
some of the main programming struc-
tures in Processing.

8

/*
Triangle drawing program
Context: Processing

Draws a triangle whenever the mouse button is not pressed.
Erases when the mouse button is pressed.
*/

NOTE: All code examples in this topic
will have comments indicating the
context in which they're to be used:
Processing, Processing Android mode,
Arduino, PHP, and so forth.

// declare your variables:
float redValue = 0; // variable to hold the red color
float greenValue = 0; // variable to hold the green color
float blueValue = 0; // variable to hold the blue color

// the setup() method runs once at the beginning of the program:

void setup() {
size(320, 240); // sets the size of the applet window
background(0); // sets the background of the window to black
fill(0); // sets the color to fill shapes with (0 = black)
smooth(); // draw with antialiased edges
}

// the draw() method runs repeatedly, as long as the applet window
// is open. It refreshes the window, and anything else you program
// it to do:

void draw() {

// Pick random colors for red, green, and blue:
redValue = random(255);
greenValue = random(255);
blueValue = random(255);

// set the line color:
stroke(redValue, greenValue, blueValue);

// draw when the mouse is up (to hell with conventions):
if (mousePressed == false) {
// draw a triangle:
triangle(mouseX, mouseY, width/2, height/2,pmouseX, pmouseY);
}
// erase when the mouse is down:
else {
background(0);
fill(0);
}
}