# September 4

## 15-104 Lecture 3 Notes, 9/4/15

Prof. Roger B. Dannenberg

Once again, this is an outline and some pointers to material.

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### Introduction to Using Variables

``````// Learning Processing
// Daniel Shiffman
// http://www.learningprocessing.com
// Example 4-2: Using variables
// Declare and initialize two integer variables at the top of the code.

var circleX = 100;
var circleY = 100;

function setup() {
createCanvas(480, 270);
}

function draw() {
background(255);
stroke(0);
fill(175);
// Use the variables to specify the location of an ellipse.
ellipse(circleX,circleY,50,50);
}
``````
``````// triangle to the right of ellipse

var y = 100;
var x = 50;

function setup() {
// set canvas size
createCanvas(400, 200);
}

function draw() {
// set background color
background(200, 200, 225);

// set a fill color (red, green, blue)
fill(0, 180, 180);
// set stroke properties
stroke(0, 0, 255);
strokeWeight(10);
// draw a circle
ellipse(x, y, 100, 100);
// set a new fill color
fill(255, 0, 0);
// set a new stroke property
noStroke();
// draw a triangle
triangle(x + 100, y + 50, x + 150, y - 75, x + 210, y + 50);
}
``````

### Mouse Input

``````function setup() {
createCanvas(400, 400);
}

function draw() {
background(200, 250, 200);
ellipse(mouseX, mouseY, 100, 100);
// try this:
// ellipse(100, 100, mouseX, mouseY);
}
``````