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Many of the tutorials for Processing concentrate on what the language

the programs at <a href="http://openprocessing.org/">openProcessing.org</a>.

You wouldn&rsquo;t think of building a house without a blueprint, and you

keyboard. So that&rsquo;s where I started.

The first step was to draw a crude diagram to dredge up old memories of how regular

So, if you have a line of length <em>r</em> starting at (0,0) at an angle theta (&theta;),

what are its coordinates in terms of <em>x</em> and <em>y</em>? If you know a little bit of

<p><img src="imgs/sketch2.jpg" alt="Diagram of angle showing relationship of cosine and sine"

width="250" height="164" /></p>

It looks like this is a job for a <code>for</code> loop that runs from 0 to

<em>n</em> (the number of sides), calculating the points for each vertex and drawing

The program works, so it&rsquo;s time to see if there are things that

could be added or changed. First, the triangle and pentagon seem

the vertices were within the proper area.

I now had a much more flexible function for drawing polygons, but

it came at the expense of more parameters. It would be nice to be

What happens if someone tries to draw a polygon with 2 sides, 1 side,

or worse, 0 sides? The first two will generate a line and a point,

Now that I was satisfied with the <code>polygon()</code> function, it was time

to move on to drawing stars. From some playing around with a crude sketch, I

When I ran this program, I just freaked out. Everything looked great,

except for the three-sided star. How come I didn&rsquo;t

Finally, in order to use the functions in something other

than a test, I decided to write a program that

Now that I have working functions for polygons and stars, it might

be useful to make a <code>Polygon</code> and <code>Star</code> class

a tutorial about objects in Processing.</a>

This tutorial has shown you the things you never see in books.

In a book, all the diagrams are

You can <a href="code/polystar.zip">download the files from this tutorial</a>.

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Before we begin programming with Processing, we must first channel our eighth grade selves, pull out a piece of graph paper, and draw a line. The shortest distance between two points is a good old fashioned line, and this is where we begin, with two points on that graph paper.

<br /><br />

<br /><br />

<img src="imgs/1.2.jpg">

<br /><br />

<br /><br />

Nevertheless, there is a catch here. The graph paper from eighth grade ("Cartesian coordinate system") placed (0,0) in the center with the y-axis pointing up and the x-axis pointing to the right (in the positive direction, negative down and to the left). Th e coordinate system for pixels in a computer window, however, is reversed along the y-axis. (0,0) can be found at the top left with the positive direction to the right horizontally and down vertically.

<br /><br />

<img src="imgs/1.3.jpg">

The vast majority of the programming examples you'll see with Processing are visual in nature. These examples, at their core, involve drawing shapes and setting pixels. Let's begin by looking at four primitive shapes.

<br /><br />

line(110,150,120,160);

</p>

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In the digital world, when we want to talk about a color, precision is required. Saying "Hey, can you make that circle bluish-green?" will not do. Color, rather, is defined as a

range of numbers. Let's start with the simplest case: black & white or grayscale. 0 means black, 255 means white. In between, every other number - 50, 87, 162, 209, and so on - is a

<br /><br />

<img src="imgs/order.jpg" border="1">

<img src="imgs/rgb.png" width = 200><br />

<br />

<br /><br />

<img src="imgs/selector.jpg" border=1>

In addition to the red, green, and blue components of each color, there is an additional optional fourth component, referred to as the color's "alpha." Alpha means transparency and is particularly useful when you want to draw elements that appear partially see-through on top of one another. Th e alpha values for an image are sometimes referred to collectively as the "alpha channel" of an image.

<br /><br />

rect(0,150,200,40);

</pre>

RGB color with ranges of 0 to 255 is not the only way you can handle color in Processing. Behind the scenes in the computer's memory, color is always

talked about as a series of 24 bits (or 32 in the case of colors with an alpha). However, Processing will let us think about color any way we like, and

<br />

With <a href="http://processing.org/reference/colorMode_.html"><strong>colorMode()</strong></a> you can set your own color range.

</p>

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This tutorial introduces you to the three types of curves in Processing:

arcs, spline curves, and B&eacute;zier curves.

Arcs are the simplest curves to draw. Processing defines an arc as a section of an ellipse.

Arcs are fine, but they&rsquo;re plain. The next function,

<code>curve()</code>, lets you draw curves that aren&rsquo;t

lets you do just that.</a>

In isolation, a single <code>curve()</code> is not particularly appealing. To draw a

continuous curve through several points, you are better off using

Though better than arcs, spline curves don&rsquo;t seem to have those

graceful, swooping curves that say &ldquo;art.&rdquo; For those,

lets you do just that.</a>

Just as <code>curveVertex()</code> allows you to make continuous

spline curves, <code>bezierVertex()</code> lets you make continuous

endShape();

<li>Use <code>arc()</code> when you need a segment of a circle

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</table>

<table width="656">

<tr>

Before we begin programming with Processing, we must first channel our eighth grade selves, pull out a piece of graph paper, and draw a line. The shortest distance between two points is a good old fashioned line, and this is where we begin, with two points on that graph paper.

<br /><br />

<br /><br />

<img src="imgs/1.3.jpg">

The vast majority of the programming examples you'll see with Processing are visual in nature. These examples, at their core, involve drawing shapes and setting pixels. Let's begin by looking at four primitive shapes.

<br /><br />

line(110,150,120,160);

</p>

</td>

</tr>

</table>