Processing: Creative Coding and Computational Art

Figure 11-13. Weight on a Spring sketch
Notice the actual springing code in the setSpring() function:
// spring behavior
y += cos(radians(angle))*amplitude;
amplitude*=damping;
angle+=frequency;
This code is very similar to other trig expressions used throughout the book. Again, by
damping a simple sine or cosine wave over time, you can create pretty realistic spring
motion. Lastly, notice within the createSpring() function that I used the modulus operator
(%) when drawing the spring. I needed a way of alternating the plotting of the spring
coil right and left. By using the if...else block with the condition (i%2==0)—only an
even number leaves a remainder of 0 when divided by 2—I was able to accomplish this
easily.
We can build upon this concept by simulating some values for mass and spring strength. In
the next sketch, shown in Figure 11-14, I create a series of springs that have varying sizes
(representing differences in mass) and spring strengths, illustrated by varying the stroke
weight when drawing the springs. Based on these variations, the sketch simulates how
these different configurations might move. For example, a heavy weight attached to a
spring with a small rod diameter would stretch further than the same weight on a spring
with a wider diameter. The damping effect of the spring is based on the stroke weight as
well. Each time you run the sketch or click the mouse in the display window, random
values are generated for mass and spring strengths.
// Weights on Springs
int weights = 5;
float[]x = new float[weights];
float[]y = new float[weights];
float[]w = new float[weights];
float[]h = new float[weights];
float[]angle = new float[weights];
MOTION
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